REDESIGN OF A
SUBMERSIBLE AUTONOMOUS DATA
COLLECTION AND TRANSMISSION SYSTEM
(S.A.D.C.A.T.S.)
PRELIMINARY DESIGN REPORT
Department of Mechanical Engineering
Department of Electrical Engineering
Kate Gleason College of Engineering
Rochester Institute of Technology
76 Lomb Memorial Drive
Rochester, NY 14623-5604
Design Team 34
09 March, 2016
Matthew Rhoads
Matthew Buchwald
Matthew DeHaven
John Robinson
Daniel Rubin
Matthew Stith
Executive Summary
This report is a summation of the collaborative work produced by the persons defined
within to achieve a reworking of a Submersible Autonomous Data Collection and
Transmission System (SADCATS) for utilization in naturally formed bodies of water. The
end product is intended to serve the needs of The Chester F. Carlson Center for Imaging
Science as well as the Biology Department of The State University of New York College
at Brockport. The goal is thus to design and fabricate a vessel that is capable of data
collection in the scope of spectral irradiance, pressure, temperature and turbidity.
Improvements have been achieved in the areas of data transmission, geo-location and
weight. This year’s design also incorporates capabilities for directed surface locomotion
which were not available on the original design.
The design process of this years design incorporates multiple facets of the Engineering
Design Planner™ as developed by Dr. Edward Hensel, PE. To this date, the facets
involving the concept development and paper design phase have been completed.
These facets include recognition and quantification of the need, concept development,
feasibility assessment, design and performance parameters, analysis and synthesis of
design elements, and a report of the current status of the project, including a project
outlook. Preliminary design documentation in the aspect of a technical data package
has also reached fulfillment at this time.
Through this design process, the idea of the data collection submersible vessel evolved.
The design decided on for the second generation of SADCATS will incorporate both
surface navigation and static diving. A ballast system in the rear of the sub will be used
to control diving via an air/water bladder. The vessel will only be capable of surface
navigation by using two propellers mounted on the side of the vessel. These propellers
will not only control forward propulsion but will also be used to change direction. The
sensors that will be used include temperature, pressure, color, and turbidity along with a
GPS module.
The technical data package portion of this report has been developed to incorporate
relevant Computer Aided Design (CAD) documentation for the finalized design.
Supplementing the CAD drawings, electrical flow diagrams and schematics of all
relevant systems have been integrated into the package. All relevant computer coding
and syntax has also been included for review as necessary.
Following the review of the Preliminary Design Report, the production and testing phase
of the project will commence. The design will be fabricated, and assembled. It will then
be calibrated and tested for conformity to the project sponsors specifications. After the
relevant testing period has been completed, the finalized physical model will be
delivered to the project sponsor for deployment and utilization.
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Table of Contents
Executive Summary
Table of Contents
Table of Illustrations
1.0 Recognition and Quantification of the Need
1.1 Mission Statement
1.2 Definition of Involved Parties
1.3 Product Description
1.4 Scope of Limitations
1.5 Project Goals
1.6 Financial Parameters
1.7 Primary Market
1.8 Secondary Market Possibilities
2.0 Concept Development
2.1 Surface Vessel Concept
2.2 Solar Vessel Concept
2.3 Dynamic Submersible Concept
3.0 Feasibility Assessment
3.1 Surface Vessel Assessment
3.2 Solar Vessel Assessment
3.3 Dynamic Submersible Assessment
3.4 Resultant Concept from Feasibility Assessment
4.0 Design and Performance Parameters
4.1 Design Objectives
4.2 Performance Specifications
4.3 Design Practices Utilized
4.4 Safety Concerns
5.0 Analysis and Synthesis of Design Elements
5.1 Mechanical Design
5.1.1 Hull
5.1.2 Ballast System
5.1.3 Propulsion System
5.1.4 Stability Control
5.1.5 Component Mounting System
5.2 Electrical Design
5.2.1 Microcontroller Selection and Design
5.2.1.1 Selection of Microcontroller
5.2.1.2 Integration with Electrical System
5.2.1.3 Organization of Program Structure
5.2.2 Power Electronics Board
5.2.2.1 Diodes (Vishay, 1N5820)
5.2.2.2 Power FETs (Motorola, IRF540)
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5.2.3 Communications
5.2.3.1 Modem and Radio Transceiver
5.2.3.2 Radio Amplifier, and Tx/Rx switch
5.2.3.3 GPS
5.2.3.4 Antenna
5.2.3.5 Data flow, error detection and error correction
5.2.3.6 Legal Restrictions
5.2.4 Data Acquisition and Sensory Package
5.2.4.1 Pressure Sensor
5.2.4.2 Temperature Sensor
5.2.4.3 Turbidity/Conductivity Sensor
5.2.4.4 Color Sensor
5.2.5 Power Sources
5.2.5.1 Selection of battery chemistry
5.2.5.2 Determination of Battery Capacity/ Configuration
5.2.5.3 Power Management
5.2.5.4 Battery Voltage Sensing, Power Redundancy, Power Switching
5.2.6 Electromechanical Devices
5.2.6.1 Motors
5.2.6.2 Pump
5.2.6.3 Solenoid Valve
5.3 Lighting
5.4 Analytical Conclusion
6.0 Status and Outlook
6.1 Obtainment of Components and Materials
6.2 Fabrication
6.3 Testing and Calibration
6.4 Budget
6.5 Project Completion Timeline
7.0 Conclusion
References
Appendix
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Table of Illustrations
A
Table 5.2.1
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1.0 Recognition and Quantification of the Need
1.1
Mission Statement
The Submersible Autonomous Data Collection and Transmission System Team
is to design and fabricate a functional prototype to be delivered to the project
sponsor for use in data collection. The prototype is to be a second generation
offspring of the model produced during work conducted in the year prior. The
model also is to be designed so as to not loose any of the functionality provided by
the previous design.
1.2
Definition of Involved Parties
Project Sponsor:
Dr. Robert Kremens
Senior Research Scientist
Chester F. Carlson Center for Imaging Science
College of Science
Rochester Institute of Technology
Team Mentor:
Dr. Wayne Walter
Tenured Professor
Mechanical Engineering
Kate Gleason College of Engineering
Rochester Institute of Technology
Project Group Leader:
Matthew Rhoads BS ME
Project Group Members:
Matthew Buchwald MS/BS EE
Matthew DeHaven BS ME
John Robinson BS ME
Daniel Rubin BS ME
Matthew Stith BS EE
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1.3
Product Description
While significant resources have been allocated to research of the offshore
regions within the Atlantic and Pacific Oceans; the quantity of data available from
shallow lake research pales in comparison to the oceanic data available.
Currently, data collection is carried out in a labor intensive manual fashion, often
times via a bucket method, where specimens must be transported back to dry land
for analysis.
This tends to lead to issues of data inaccuracy resultant from
contamination during transport, and the variation of environ between eco-system
and laboratory. Thus it was proposed that an autonomous system be developed to
aid in the acquisition and transmission of relevant data from the point of origin back
to a base station for distribution and analysis.
The device in question was to be designed such that the capabilities of the first
generation prototype are maintained.
At the same time, improvements in
communication, dry weight, geo-location capability, horizontal motion, and sensor
feedback were to be realized.
Specifically, the project sponsor provided three scenarios under which the vessel
could be deployed. The design team was informed that the project design could
be made to address one of the scenarios, or to incorporate the means to be
deployable in a multitude of situations.
Scenario:
A. Surface Water Temperature Mapping
Water acts as an ideal blackbody emitter and therefore is a valuable calibration
source for detectors of radiant flux. Thus Landsat,
EO-1 and other satellites
are calibrated using the lake. On an “overflight” day, GPS measurements and
water surface temperatures are taken at about the time the satellite is
overhead.
Consequently a surface vessel could be designed to relay position and
temperature data to fixed station that serves up info on the web. A lifetime of
two orbital passes, which typically takes 11-12 days, would be required.
Inclusion of a measurement device for downwelled radiance, light that hits the
surface of the water form all sources direct and reflected, was also desirable.
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B. Submersible Data Acquisition
A device capable of taking temperature depth profiles, in Lake Ontario and
Conesus Lake, to a depth of 20 to 30 meters was another possibility. GPS was
to be utilized for positional feedback along with data collection telemetry and a
radio transmitter to transfer the data to a base station. The data collection
telemetry was to include temperature and turbidity as a function of depth and
time. High time resolution is required at a rate of one measurement every
minute, especially during rain events. The radio range was to be approximately
18 miles in radius about the base station located at RIT in Rochester)
C. Boats/Buoys with Full Directional Control
The
ideal
device
was
to
measure
surface
temp,
water
color,
brown/green/yellow, and downwelled light thus amounting to maybe 6 channels
of data. Again GPS was to be utilized for positional accuracy, with radio range
similar to that of Scenario B.
Throughout the design, for any or all missions, the most important features were to
be:




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Position awareness via GPS telemetry
Mechanical design to suit the mission profile
Cost effective design
Simple design
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1.4
Scope of Limitations
The SADCATS product design phase is to be completed by the conclusion of Fall
Quarter (14 November, 2003) and is to include the following deliverables:

Preliminary Design Documentation

Graphical Representation of the Elements Required to Construct the
Design

Bill of Materials, Price Quotes, and Purchase Orders for Elements

Design Presentation and Defense During Preliminary Design Review
The SADCATS product fabrication and testing stage is to be completed by the
conclusion of Winter Quarter (20 February, 2004) and is to include the following
deliverables:

Working Physical Prototype

Finalized Design Documentation

Testing and Calibration Results

Team Binder of Data Collected During the Design Phases
The SADCATS team members ARE NOT responsible for:
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Deployment of the Prototype

Development of Individual Components of the Design

Component Integration rather than Fabrication

Reception of Data at Base Station

Relay of Data to Secondary Market Customers
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1.5
Project Goals
The project will meet successful completion when the following facets have been
met:

The project team members have developed the necessary skills to become
an integral part of the multi-disciplinary engineering design process

The project team members have learned the appropriate analysis
techniques as required by the design process

The final prototype product meets and or exceeds the goals and
expectations imposed by both the project sponsor and the design team.

The final prototype has been completed within the budgeted time and
financial allotments

The project’s results provide a basis for further development and or data
acquisition.
1.6
Financial Parameters
The budget for the SADCATS project is tentatively set at $1000.00, and is to
include:
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
Raw Materials Required for Vessel and Skeleton Construction

Data Acquisition Sensors

Lighting Elements

Motor(s)

Propeller(s)

Pump

Dive System Components

Hydraulic Lines and Fittings

Power Source(s)

General Hardware
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Electronic components are to be sourced first via the project sponsor.
Specifically the sponsor is to provide:

GPS Unit

Radio Communications Equipment

Electronic Controller Hardware
The possibility for some limited fabrication of parts via the sponsor does exist.
1.7
Primary Market
The primary market sector for the SADCATS project is defined as the project
sponsor. This consists primarily of Dr. Robert Kremens of the Imaging Science
Center.
1.8
Secondary Market Possibilities
Secondary market possibilities exist in the provision of data acquired by the
SADACATS device for use and interpretation by the following:



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The State University of New York College at Brockport
Calibration of Landsat, E0-1 and similar Satelites
Other Parties interested in Research Data in Shallow Water Bodies
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2.0 Concept Development
Initial concept development for the SADCATS design began with a brainstorming
session to bring to light possible solutions to the proposed topic areas inclusive to
section 1.3 of this report. The brainstorming session produced a long list of twenty
concept ideas which can be found in Appendix A.1. In order to obtain the greatest
benefit from this initial concept development stage, no idea was left uncovered and
every idea has been documented. Through group discussion and a team polling
procedure, the long list was narrowed to the three concepts described below.
While the three selected concepts contain distinct variances, all relevant original
concept components have been retained.
Due to the variability of the project
statement by the sponsor, specific design concepts may be found to be inherently
biased toward a given sector of project development.
Found hereafter, is an in depth description of the three top concepts. While not
intended to actually represent the finished design product, they are meant to
portray possible solutions to the above design criteria while maintaining the
general physical properties consistent with products similar to the aforementioned
conceptual models. Also included, the electrical block diagrams are intended to
give a general feel for the integration and interaction of required components within
the design envelope.
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2.1
Surface Vessel Concept
The surface vessel concept arose directly from the concept reduction process.
The main drive for a surface vessel capable of the required tasks was a reduction
in complexity over that of a submersible vessel.
The design team thought that the surface vessel could be “overbuilt” to enable
future modifications to make the vehicle a submersible.
Creating extra space
would also allow for further additions of sensing and communication technology.
The concept of the surface vessel incorporates two motors which extend
outboard from the hull. The motors would be located away from the body of the
vessel to ease turning. The motors would be configured to be under the water line
to allow the propellers to have full contact with the water. A rudder was planned
for the bottom of the vehicle to aid in vessel stability. The components of the
surface vessel would be mounted in the center and near the bottom of the hull.
The location of the internal components is critical to allow the vehicle to be upright
in the water.
Since this is a vehicle that operates on the surface of the water, it would
also have navigation lights designed to increase safety. Other boats must be able
distinguish water from this vessel so they can avoid a collision. Since the vessel is
small in size, and low speed, the most effective solution would incorporate a white
light viewable 360 degrees around the vessel.
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2.2
Solar Vessel Concept
During the initial design phase of the project, one of the main areas of interest
was that of solar cell power. The idea mainly arose from the desire to have an
active way to replenish and or increase the power capacity of the vessel. Thus the
two main scenarios for operation were in that of a vessel obtaining all of its
required power via solar means, and a vessel that would use to solar cells to
recharge batteries that would in turn power the vessel.
In addition to the possibility of using solar cells, one group member suggested
using a sail to provide some to all of the navigational power, thus allowing for the
solar cells to only provide enough energy to power the data acquisition equipment.
As the solar vessel was mainly thought of as a surface going craft, the data
acquisition and telemetry design would be similar to that of the electric surface
vessel, and as such the vessel would be best suited to the Scenarios A and C of
Section 1.3.
Electrically, the solar vessel would require the addition of the cells themselves,
and a battery recharging board to regulate the replenishment of battery power.
Mechanically, a device to orient the solar panels would also likely be needed.
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2.3
Dynamic Submersible Concept
Keeping in tune with the development work conducted in the prior generation of
SADCATS, the main concept was the development and construction of a
submersing vessel.
Thus the concept would be capable of meeting all of the
scenarios of Section 1.3.
The initial submersible concept development looked at the inherent benefits of
both open and closed frame designs. The main scope of the initial submersible
was to contain dynamic motion capabilities both above surface and below, via a
design that would be inherently productive in both scenarios. Said design would
thus allow for a varying mission where data acquisition below surface could be
obtained, as well as surface data.
The concept model looked to achieve navigational means on surface via GPS,
and under surface via either inertial or magnetic means. Radio transmission of the
data collected would be conducted during surface dwelling time only as the radio
would not be capable of transmission while under water.
A ballasting system was to be incorporated either inboard or in connected
outboard dive tanks. From an early stage, the possibility of using two externally
mounted motor-propeller assemblies on opposite sides of the vessel was
incorporated.
Moveable control surfaces were discussed in an effort to aid in
navigational capabilities. The submersible would carry a similar sensory package
to that of the surface vessel, with the addition of pressure and turbidity sensors for
use when submersed.
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3.0 Feasibility Assessment
3.1
Surface Vessel Assessment
Navigation was one of the primary concerns of the project. As such, it became a
large part of the driving force behind designing a service vessel.
Underwater
navigation is difficult due to the presence of location control where as surface
navigation provides a means for satellite communication via GPS.
The GPS
system used under last years design was found to be sufficient for all required
mission parameters, and provides easy integration.
The radio transmission
capabilities for the surface vessel are also easily accomplishable, and again the
equipment utilized in the prior generation could be incorporated.
The surface vessel would be able to take measurements of surface temperature,
water color, and down-welled radiance. By the general nature of the design, the
vessel would not be able to acquire information from water at depths greater than a
foot or two under the surface without a deployable means of “dropping” sensors to
greater depths.
To address the issue of underwater data collection, a tether was investigated as
a way to have surface mobility while still maintaining the ability to take
measurements of the water below. If the tether was long enough, it would be able
to reach up the desired depth of 100 feet. However, there is no way to make sure
the tether would drop straight down. The hanging tether also presents snagging
hazard to the device. A hanging cable 100 feet long is bound to get stuck on
something sooner or later. A built-in location error that is a result of the GPS
system must also be considered. The combination of the errors would make for
unreliable underwater data collection.
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3.2
Solar Vessel Assessment
For the best efficiency, the solar panels would need to be angled toward sunlight.
Thus the design of a mechanism to tilt the solar cells such their orientation would
allow for the absorption of maximum sunlight would need to be incorporated. This
in turn leads to additional complexity within the control system.
If the vessel
submerged, it would also complicate the dive systems due to the added
mechanical parts.
If the panels were fixed and not controlled to correct with
sunlight, they would still require integration with the hull, which adds difficulty in the
area of watertight design.
Due to the constant motion of the water’s surface, a tilt mechanism would likely
not be able to maintain the proper angle, and the solar panels would therefore be
subject to a somewhat random ability to receive solar radiation. It would be difficult
if not impossible to ensure that the panels would even be angled towards the sun.
As solar panels only absorb a certain range of wavelengths of electromagnetic
radiation, they will not absorb all the available energy from a panel even when at
maximum angle. This may be as low as 15% of the total possible power due to
electromagnetic radiation.
Average yearly available sunlight for the Rochester area is roughly 50%, which
determines that the panels will not always receive sufficient sunlight. As of 1990,
the solar radiation in the area would yield roughly 2.5kWh/m² per day. As the
panels that could be integrated within the vessel would be small in size, the power
generated by the cells would be relatively low.
The absence of sunlight on
particularly cloudy days is unpredictable. Therefore even when on the surface, the
vessel would not be guaranteed to receive sufficient power from the cells. In this
case, the cells would merely be added weight, thus adding to the power required to
propel the vessel through the water.
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3.3
Dynamic Submersible Assessment
Due to the inherent properties of water as a medium of submersion, the first
issue encountered in the analysis phase of the concept was that of underwater
navigation. GPS signals are not able to be used in underwater environ due to the
scattering of the signal as it hits the water’s surface. This led to research into the
areas of inertial navigation and magnetic navigation.
On the topic of inertial navigation, it was determined that many ocean going
research submersibles utilize pre-made inertial navigation systems. Unfortunately,
these systems tend to be large in physical size. Smaller versions are available, but
were found to be beyond they financial scope of the project at hand.
Another option in the realm of inertial navigation was that of creating a custom
package using accelerometers purchased from an outside source, and utilizing a
custom circuit. From the standpoint of cost and mechanical feasibility this was a
viable option, but the programming for such a device was seen to be quite
complex, and thus, due to limited project development time, this option was also
surpassed.
Digital, steady-state magnetic devices are also available on the common market.
Again research was conducted into pricing and integration into the overall design
of the vessel. Unfortunately, due to the limited budget, and the complexity of the
algorithm requited to process the data feedback from the device, magnetic
navigation was ruled out.
While research was being conducted into the navigational control facet of the
design, research was also conducted into the possibility of mobile control surfaces
for underwater application. It was found that the sealing of any actuator rods and
other linearly mobile items would be somewhat difficult.
From a ballast standpoint, the design team was limited only by imagination in the
area of design. Both external and internal ballast tank systems were considered.
The main drawback in many of the commonly applied systems was found to be an
excessive dry weight. In looking at the previous generation SADCATS device, one
soon finds that a good majority of the weight, and the reason for such a large
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vessel, is directly correlated to the issue of the scuba tank used to purge the
ballast water from the ballast tanks.
Not only does the weight of the tank play into weight hindrance, but if one looks
at the physical size of the tank, they find that volumetrically there is a large quantity
of displacement, which creates a high buoyancy force that must be overcome in
order to provide diving capability. Consequently, it was determined that the system
must be both significantly lighter and much smaller in size than commercially
available systems.
Lastly under consideration when building a submersible, is the issue of pressure
vessel design. A main concern with the GPS module was the issue of metallic
enclosure. Thus it was decided that at the least, the section of hull in which the
GPS is located would have to be constructed of a non-metallic material.
Investigation into the capabilities of in-house welding also proved that metallic
construction was likely out of the question due to concerns for a water tight seal at
pressure.
3.4
Resultant Concept from Feasibility Assessment
Further analysis was conducted to determine which of the above concepts would
best meet the needs of the design project. A list of criteria that would be
incorporated into the design was constructed. The listed consisted of weight, cost,
reliability, adaptability, difficulty, part availability, life span, package, serviceability,
communications, power consumption, and capability.
Definitions of Criteria:
Weight: total weight of deployable device
Cost: total cost of parts and man hours to put together device
Reliability: accuracy of data
Adaptability: ability to add more parts in the future, space for expansion, easy to
modify
Difficulty: will the group be able to build debug to intended design function
Part Availability: ease of acquiring parts to build and replace in order to service
when repair is needed
Life Span: length of mission the device as able to sustain measuring devices
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Package: ease of fitting all components inside the hull
Maintenance: ease of repair, device must fairly easy to disassemble and fix
Communication: ability of device to transfer data to base station for
analysis
Power Consumption: power used by device
Capability: the number of tasks the vessel can achieve
Once all of the criterion were determined and defined, Pugh’s Method was
utilized to assign weight to each of the variables.
After the criteria were weighted according to their importance (Appendix A.1),
they were crossed referenced to the three design ideas with the surface vessel set
as the base concept. Due to the style of this method, and the quantification of a
relative increase or decrease in the given criteria, a score of three is considered
baseline. Thus, for a concept to show improvement over the baseline its combined
score must be greater than three. Results are provided in Appendix A.2.
The calculations show all the designs to be relatively similar. While the electric
surface vessel won out by a slight margin, the design team felt that the increased
capability of the submersible design should not be ignored. Upon re-inspection of
the concept feasibility voting results, it was determined that the two main shortfalls
of the submersible concept were the weight and difficulty criteria.
The concern relative to weight with regard to the submersible was mainly in the
excessive weight in the design of the ballast system. Therefore it was decided that
in order to incorporate a submersible design a significant weight reduction in the
design of the ballast system would be crucial. The group also decided that the
ballast system should not be designed in such a manner so as to prohibit the
design of a vessel capable of surface research, should a light weight ballast
system design prove to be beyond the scope of the project.
The other major shortfall, difficulty, was analyzed to determine if improvements
could be integrated into the design. The main complexity of the submersible
concept was found to be resultant from the desire to provide underwater
navigational capabilities. While surface navigation can be easily accomplished via
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the utilization of GPS, the inherent properties of a water medium provide to negate
the possibility of GPS for submerged location finding. Thus, a study into
information on the possibility of navigation via inertial means, and or utilizing
magnetic compass devices was conducted. Both means proved to be quite cost
prohibitive.
The previous generation of the SADCATS project incorporated static diving
capabilities. Even though the complexity of a dynamic-dive and submerged
navigation system was proved to be prohibited by budget and time factors for the
scope of the project at hand, the possibility existed for the incorporation of a static
dive system within the timeframe allotted.
The design decided on for the second generation of SADCATS will incorporate
both surface navigation and static diving. A ballast system in the rear of the sub
will be used to control diving via an air/water bladder. The vessel will only be
capable of surface navigation by using two propellers mounted on the side of the
vessel. These propellers will not only control forward propulsion but will also be
used to change direction. The sensors that will be used include temperature,
pressure, color, and turbidity along with a GPS module.
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4.0 Design and Performance Parameters
4.1
Design Objectives
The design and production of the SADCATS project is to be considered complete
when the following deliverables are met:
 The finalized design accomplishes all of the required tasks
o
Data acquisition is accurate and within the specified tolerances
o
Data transmission is accurate and reliable
o
The control software is robust, fully capable, and easily modifiable
o
The vessel is capable of accurate navigation via GPS
o
The vessel is light weight and easily transportable
o
The vessel and related electronics are capable of autonomous deployment
o
The vessel is able to perform its tasks over the full mission length
o
The vessel is within the required budget
 All options have been exhaustively analyzed, discussed, and processed
 The design is properly documented so that future users can benefit from the work
accomplished by this years project team
 All project deadlines, both internal and external have been satisfactorily met
 The design provides the means for addition of other payloads in the future
4.2
Performance Specifications
Among with the design objectives, there are a number of specific performance
specifications that are to be met in order for the SADCATS project to achieve
successful completion. They are as follows:
A. Dive Depth: The maximum dive depth of the vehicle is to be 100ft
B. Horizontal Speed: The vehicle is to achieve a surface speed of at least one
knot.
C. Target Mission Length: 16 Hours (Daytime Deployable)
D. Tracking Range: Data points can be taken from 30km outside Rochester
4.3
Design Practices Utilized
The SADCATS vessel has been designed utilizing the following principles:
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A. Design for Manufacture: All parts of the design have been selected and
designed with easy of manufacturability in mind. All custom parts can typically
be made on premise for users with an engine lathe and upright milling
machine.
B. Design for Assembly: The overall design of the vessel is such that it can be
constructed using commonly available tooling. It is also such that no special
training is required to assemble the vessel.
C. Utilization of Common Hardware and Materials: The design incorporates
hardware and materials that are commonly available. The end user will thus
benefit due to the easy of part replacement.
D. Design for Expandability: The vessel is structured such that additional
payload sections can easily be incorporated. This provides the user endless
possibilities for data collection and or scientific experimentation
E. Economical Design: Without compromising integrity, the design incorporates
a low cost solution, thus allowing the end user to maximize return on financial
investment
F. Recyclability: The SADCATS vessel has been designed to allow for ease of
recyclabiity. This includes the reuse of some items, and the separation and
sorting of those parts not reusable.
4.4
Safety Concerns
Due to the nature of the project, there were many safety standards to be taken
under consideration. The foremost is that of the ASME Boiler and Pressure Vessel
Code. Other design standards include, but are not limited to Cost Guard
specifications for small scale powered watercraft and research vessels, and FCC
regulations governing radio transmission. As always, electromechanical devices
present some risk of shock, and this risk is increased due to the utilization of the
design in water environ.
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SADCATS
5.0 Analysis and Synthesis of Design Elements
5.1
5.1.1
Mechanical Design
Hull
The hull of second generation SADCATS design has been modified greatly
from that of the original variant. When compared to the previous generation, the
urge to lower weight and add directed mobility were the main driving factors for
such a radical redesign. Thus the design of the hull was greatly dictated by the
internal component requirements in addition to the need for a streamlined profile
to minimize losses while in motion.
Due to the requirement of the vessel to have the capability to submerge, the
hull is subject to pressures not typically experienced during surface mobility.
When one travels below a fluidic surface, the pressure distribution experienced is
defined by the expression
P=Patm+ρgh
Equation 5.1.1
Thus as a general rule derived from the density of water as a fluidic medium, for
every 33 feet one dives, they experience one additional atmosphere of pressure.
Based on this rule, the vessel design must be able to withstand four atmospheres
of pressure.
Based on electrical requirements of the dictated GPS navigation system, the
material of the vessel was required to be non-metallic in nature, so as to not
interfere with communications between the GPS sensor and its satellite
communications. Thus it was a direct goal of the design to provide a solution
that utilized such material.
Moreover, due to propulsion and stability theory as found in sections 5.1.3 and
5.1.4 respectively, it was determined that the vessel would be most stable when
the latitudinal cross section was symmetric about the vertical plane traveling
through the geometric midpoint of the vessel.
In an effort to reduce drag,
contoured surfaces were investigated. The geometric strength of the design was
also analyzed due to the external pressures seen during service. In addition, the
possibility of internalizing the ballast system was investigated.
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SADCATS
The resultant hull design was dictated largely by concerns for structural rigidity
and low resultant drag. The above considerations where also included in the
analysis.
As the sponsor is providing a means the outsourcing of some
fabrication tasks, the hull design also reflects discussion with the fabrication
facility.
The second generation SADCATS hull design thereby incorporates the use of
three composite materials in its design. The need for color sensing technology
provided a necessity for a transparent hull portion to allow for light feed back to
the color sensor.
Therefore Plexiglas Acrylic has been selected for the
hemispherical front section.
The Plexiglas material will provide machinability
during the fabrication phase, while maintaining high optical qualities as required.
The center sections of the hull have been designed to be fabricated from
Schedule 80 Polyvinylchloride (PVC) pipe. Due to the need to compartmentalize
the hull sections, PVC was chosen as a low cost solution to the need for a
durable material that would provide easily modifiable components.
Finally, the tail section is to be comprised of Acrylonitrile Butadiene Styrene
(ABS) material. The ABS material provides excellent mechanical properties and
an inherent easy of machinability. It thus provides a means for the internalization
of the ballast system in the rearward section of the submersible.
The American Society of Mechanical Engineers (ASME) Boiler and Pressure
Vessel Code was used to derive a means for the proper specification of material
thicknesses and verification techniques for the hull design. As dictated by the
ASME in Section X, the vessel is to be considered a Class II vessel and due to
service under both external and internal pressure, is to be analyzed via Finite
Element Analysis (FEA) for stress and deformation under load as specified by
Method B of Section RD-11. Material Data Properties for the hull materials can
be found in Appendix with corresponding FEA results in Appendix. The following
table provides results for the analytical analysis of the hull, based on a wall
thickness corresponding to that of Schedule 80 PVC piping, and calculations
provided in Section RD-11 for Method A design.
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SADCATS
Table 5.1.1
Design Based Parameters
Hemispherical End-Cap
Do
Outter Radius of Vessel
6.625 in
Material: Plexiglas (Acrylic)
EABS 348091 psi Allowable External Pressure
PaEXT 1413.03 psi
Tensile Modulous
Tensile Modulous
Tensile Modulous
Cylindrical Design Factor
EPLG
EPVC
FC
449617 psi
362594 psi
5
Hemispherical Design Factor
Length of Section
Length of Tapered Section
FH
L
l
10
40 in
4.98 in
Target External Pressure
Internal External Pressure
Outter Spherical Radius
PE
PI
Ro
90 psi
150 psi
3.3125 in
Tensile Strength
Tensile Strength
Cylindrical Section
Material: PVC Schedule 80
Adjusted Length
Allowable External Pressure
Allowable Internal Pressure
Lc
PaEXT
PaINT
28.06 in
96.58 psi
375.73 psi
Conical Frustrum Section
Material: Lexan
SABS
6498 psi Allowable External Pressure
SPLG 10660.3 psi Allowable Internal Pressure
PaEXT
PaINT
1094.0 psi
473.82 psi
Tensile Strength
SPVC
5134 psi
Thickness
t
0.458 in
Sectional Pressure Divider
Poissons Ratio
ν
0.3
Material: PVC
Target Pressure=Design Pressure +30psi
Design Thickness
tD
0.4879 in
All Pressures ABSOLUTE
Adjusted Allowable Pressure PaEXT
199.8 psi
While the PVC Schedule 80 pipe would not be able to withstand the required
design pressure, the inclusions of divider walls between sections of the main hull
section shorten the effective length of the PVC Schedule 80 sections and thus
increase the range of operation pressure.
Based on the initial calculations under the scope above, the vessel was
designed utilizing the PTC Pro/Engineer and Pro/Mechanica analysis packages.
With the solid model created, the vessel structure was subjected to loading in the
three following cases:

Full Ballast System to Achieve Dive from Surface: 165psi internal pressure

Empty Ballast System at Depth for Accent: 90psi external pressure

Combined Loading State: 90psi internal and 165psi external pressures
The analytical results are provided in Appendix !!!!!!!. From the resultant
models, it can be found that maximum material deformation is with in reasonable
tolerances for the scope of the project. The stress loadings of the vessel are also
within the specifications dictated by the ASME pressure Vessel Code
5.1.2
Ballast System
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One of the major downfalls to the first generation SADCATS design was the
weight of the ballasting system.
The previous system required the need to
transport compressed air in order for the vessel to regain positive buoyancy after
a dive. Thus a major design consideration of the second generation dive system
was to allow for the ability to submerse and resurface without carrying excessive
weight as a functional requirement.
Another specific requirement derived from the desire for a mixed mission
capability incorporating surface travel was the need to create the capability to
rotate the vessel upon its horizontal axis when diving. With the negation of
dynamic diving capabilities, it was determined that this style of dive was most
logical in nature. Thus the ballast system has been designed to create a moment
such that the vessel will orient itself tail down during the dive phase. Decent and
accent are both then accomplished in a near vertical manner, with the tail
mounted water outlet serving to aid in thrust during the accent.
From a design standpoint, the ballast system is required to alter the buoyancy
of the vessel from a positively buoyant, surface mode to a negatively buoyant,
diving mode.
For the vessel to hover at a specific depth the buoyancy of the
vessel must be neutral. As the force of buoyancy is defined as
 F   ρgdV
Equation 5.1.2
As the vessel displaces a volume that is dictated by its height in its submersion
medium, the permissible weight of the vessel is directly correlated to its desired
“ride height” in the water.
In turn, the static ride height of the vessel then dictates the requirement for the
ballast weight necessary to create neutral buoyancy. The ballast system is then
designed to allow the vessel to add mass to achieve a neutrally buoyant state to
allow for the dive condition.
The table below lists the ballast system
characteristics for the SADCATS ballast system, based on critical design
parameters derivative of the hull design process.
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Table 5.1.2
Design Based Parameters
External Vessel Diameter
D
6.625
Tapered Frustum Diameter
d
3.000
Cylindrical Vessel Length
L
30.00
Wall Thickness
t
0.458
H2O Ballast Volume
Vw 244.10
H2O Ballast Volume
Vw
4.00
Conical Half Apex Angle
α
20
in
in
in
in
in³
Liters
°
Calculated Design Parameters
External Vessel Radius
R 3.3125 in
Tapered Frustum Radius
r
1.5 in
Tapered Sectional Length
l
4.98 in
(1 slug=1 lbf-s²/ft)
Mission Based Parameters
Atmospheric Pressure
Patm 14.69 psi
Air Temperature
TA
70.0 °F
Tw
Water Temperature
50.0 °F
Maximum Dive Depth
Waterline Height
Mission Parameters
d
100.0 ft
h
5.00 in
Physical Constants
Density of Water
ρ
1.94 slug/ft³
Gravitational Acceleration
g
32.17 ft/s²
Molecular Mass of Air
M
28.97 lbm/lbmol
Universal Gas Constant
R
1545 ft-lbf/lbmol-°R
Resulting System Data
Total Volumetric Displacement
VT 1186.1
Total Ballast System Volume
VB 319.65
VB
Total Ballast System Volume
5.24
Total Wetted Volume
VWET 978.65
mD
Displaced Mass
35.35
Required Air Pressure
Pc
30.0
mA
Mass of Air
0.04
H2O Mass Required to Hover
mh
7.50
H2O Volume Required to Hover
Vh 207.45
H2O Volume Required to Hover
Vh
3.40
H2O Pressure at Hover
Ph
85.47
H2O Mass at Full Dive
md
8.82
H2O Pressure at Full Dive
Pd 126.93
H2O Pressure at Depth
Pw
58.04
Maximum Dry Mass w/o Air
mD
35.31
Maximum Dry Mass
mT
35.35
Total Mass Under Full Dive
m
44.17
in³
in³
Liters
in³
lb
psi
lb
lb
in³
Liters
psi
lb
psi
psi
lb
lb
lb
The second generation SADCATS ballasting system therefore implements a
pressure differential system accomplished via the use of a water bladder
enclosed within a pressurized air chamber. As water is introduced via pump into
the bladder to add mass and change buoyancy, the air is pressurized above its
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SADCATS
static condition. The water is then expulsed through the tail section of the vessel
via the accumulated pressure under the control of a solenoid valve. A Schrader
valve allows for ease of filling and adjustment to the internal air pressure. A
pressure sensor installed in the ballast wall provides feedback to the controller,
which can open the solenoid valve in an emergency situation.
Diagram 5.1.1
P-7
P-7
P-8
Solenoid Valve
E-3
Inlet Pump
Water
Bladder
V-1
Ballast Tank
V-2
E-2
Schrader Valve
The generation one SADCATS ballast system consumed a large portion of the
vessel volume, while this years system have been reduced to less than 25% of
total vessel volume.
The reduction in weight is significant, with the second
generation system weighing less than five pounds when dry, which in turn is only
20% of the total dry weight for the second generation SADCATS.
Provision for the dive system due to the mass transfer resultant of the ballast
system design allows a dive to full 100ft depth in a maximum of 15 seconds. The
sizing of the corresponding solenoid valve was determined imperially with the
calculations found in the following figure
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SADCATS
Figure 5.1.3
Full Ballast Tank (Diving) at Depth
Internal Pressure
External Pressure
Water Density
Velocity
Pint
Pext
ρ
V
126.93
58.04
1.94
101.1279
Psi
Psi
slugs/ft³
ft/s
Mass flow for 1/8"
Time to Neutral
Buoy
Mass flow for 1/4"
Time to Neutral
Buoy
m1/8
0.53793
lb/sec
T1/8
m1/4
2.46053
2.15173
Sec
lb/sec
T1/4
0.61513
Sec
Neutral Buoyancy to Empty Ballast Tank
Internal Pressure
External Pressure
Water Density
Velocity
Pint
Pext
ρ
V
85.47
58.04
1.94
63.819
Psi
Psi
slugs/ft³
ft/s
Mass flow for 1/8"
Time to Empty
Mass flow for 1/4"
m1/8
T1/8
m1/4
0.33948
22.09286
1.357905
Time to Empty
T1/4
5.52322
Sec
Area of 1/8" Orifice
A1/8
0.012272
in²
Area of 1/4" Orifice
A1/4
0.049087
in²
lb/sec
Sec
lb/sec
From the data above, a solenoid with a ¼” orifice was selected. It is estimated
that so equipped, the SADCATS generation two vessel would reach a maximum
velocity of less than 20 feet per second.
5.1.3
Propulsion System
Part of the required capabilities of the second generation SADCATS is the
ability to collect data at different waypoints. Calculations for propulsion take into
account various aspects of the sub and its environment. Such variables as
estimated speed, density of traveling medium, and surface area must first be
considered to find the drag force. The estimated speed of 1 knot is the value the
group decided on. The density of the traveling medium is dependent of the
temperature. Surface area was found via CAD modeling. The hull sections were
made separately and then sliced to mimic the vessel as it would sit in both 4 and 5
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SADCATS
inches submerged in water. The drag force is the reaction force the sub will
experience while traveling through the water. The drag force is important to
know because in order to obtain forward motion, the drag force must be
overcome. Refer to the below equation:
FD = ½*CD**V2*A
CD is the coefficient of drag. The coefficient of drag is solely based on the
geometry of the part that the fluid is moving over. The coefficients for each hull
section were found in table.
A flow analysis was then configured for the hull. A Reynolds Number was
found for each section of the hull for the estimated speed over the temperature
range the sub would operate in. The viscosity of the fluid, speed of the fluid and
the affected length are used to find the Reynolds number. The dimensionless
value of the Reynolds Number is an indication of the nature of the flow. The
equation to calculate for Reynolds Number can be seen below:
Re = V*L/
Ideally, we would like the sub to operate in a laminar flow. A laminar flow
means that all the molecules of the medium in which the sub is traveling in are
aligned. If the molecules of the fluid are aligned, the friction the surface
experiences, is at a minimum. For a flow to be considered laminar Re must be
less than 5x105.
The complete flow analysis for the vessel is located in Appendix.
The next consideration in relation to propulsion is thrust. Thrust is the force
exerted by the propellers to achieve motion. The value of thrust is influenced by
the major diameter of the propeller, the speed of advance, the density of the fluid
medium and the rate of rotation for the propeller. The speed of advance is our
estimated speed. The major diameter of the propeller we made as a flexible
dimension. Below is the equation for thrust:
T = *V*D3*N
Propulsion is not a perfect method of forward movement. Slippage is defined as
a ratio of the speed attained divided by the speed the vessel exerts for. The
calculation for slippage is below:
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s*(s + 1) = CT
Slippage also takes into account the thrust coefficient, CT . The thrust
coefficient is an offset to account for the propeller’s major diameter, revolutions
that the prop turns per sec and the density of the medium. The equation to
calculate for CT is below:
CT = T / *N2*D4
Pitch is a dimension of a propeller that corresponds to distance traveled per
revolution of the prop. If a prop has a pitch of 2.5 inches, its ideal performance
would provide 2.5 inches of forward motion to one revolution. The theory behind
slippage infers that a propeller doesn’t perform to specification. Slippage is a
function of a vessel’s thrust coefficient.
The torque coefficient is a factor that is a ratio of the applied thrust force with
respect to the density, rate of rotation of the prop and the major diameter of the
propeller. The equation of the torque coefficient can be seen below:
CF = FT/*N2*D5
Another factor that must be considered is speed of advance coefficient, J. J is
an independent variable that is used to find the efficiency. The speed of advance
coefficient can be found using the equation below:
J = V/N*D
Efficiency of the propeller is very critical. If the efficiency of the propeller is
known or can be closely estimated, losses can be planned and compensated for.
The efficiency of the propeller is found from a table where the speed of the
advance coefficient, the torque coefficient and the thrust coefficient are plotted
against each other.
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Left y-axis is the Thrust Coefficient, CF
Right y-axis is the Torque Coefficient, CT
The x-axis is the speed of advance coefficient, J
The calculations located below allow for determination of a motor and a propeller
simultaneously.
The propeller can be sized accordingly in order to achieve
maximum performance. Vender feedback will determine the motor. The
calculations below use an example propeller.
Propulsion Calculations
major diameter
pitch
disk area of propeller
Max Drag Force
Propeller Dimensions
D=
P=
2.52
3.9
in
in
A0=
Flow Analysis
4.99
in2
F D=
Other Variables
1.89
lbf
density of fluid

0.001123
speed of advance
revolutions per unit time
Va=
N=
40.56
66.667
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slug/in3
in/s
rps
SADCATS
Propeller Calculations
Thrust, T =
T=
VaD3N
48.595 in*slug/s2
T=
4.050
lbf
Resultant Thrust, TR =
2.160
lbf
Thrust Coefficient, CT =
T/2D4
CT =
0.241
Resultant Thrust Coefficient, CTR=
0.129
Torque, Q =
Q=
Q=
(TVa)/(2piNI)
0.45096
7.2154
lb-in
oz-in
Resultant Torque, QR =
3.848
oz-in
Torque Coeffecient, CQ =
Q/N2D5
CQ =
Resultant Torque Coefficient =
CQR =
0.01067
Slippage, s =
s=
(1+4*CT).5 -1
0.231
Ideal Efficiency, I =
I=
(1-s)/(1-s*.5)
0.870
Speed of Advance Coefficient, J =
J=
Va/ND
0.241
0.00759

A motor originally was found that met the requirements from a mechanical and an
electrical engineering standpoint. However, due to the extended lead time the order for
the motor was cancelled. Another motor was found at a local store, Dan’s Crafts and
Things, that provided similar electrical requirements but the torque was lower than
originally planned for. In testing this motor in the propulsion assembly, it was found that
the torque was not large enough to turn the propeller through the lipseal. Because of time
constraints, the next available option was a hand drill motor.During the course of
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designing the propulsion system, there were two main concerns.
The first
concern was how the system would be sealed under static and dynamic
conditions. The second concern was the alignment of the shaft under loading. A
seal around the propeller shaft must be able to prevent leakage while operating
near the surface as well as provide static sealing while diving to 100 feet.
It was advised that a radial lip seal be used to give the propulsion system
proper sealing under both conditions. The information below was found in a text
that describes the functionality of a lip seal.
An elastic circular member with a beamlike cross section is bonded
to a rigid case (figure xxx). The inner diameter of the elastomeric
beam is smaller then the shaft outer diameter. The difference
between the shaft outer diameter and lip inner diameter is called
interference. When the seal is installed, the elastomeric lip is stretched
outward, which creates a force between the sealing tip and the shaft.
(reference from lip seal book page 10)
INSERT Lip Seal FIGURE HERE!!!
The function of the lip seal is very critical. If the lip seal doesn’t prevent
leakage, water will fill up the propulsion assembly and possibly cause other
systems in the submarine to fail. Not only does the sealing ability of the of radial
lip seal affect the sub as a whole, the friction of the seal affects the ability of
motor to rotate the propeller shaft.
Previous configurations didn’t take into account the friction of the lip seal.
After assembling the system it was found that a motor with greater torque
capabilities would be required to overcome the friction of the lip seal.
Other locations where sealing must be taken into account are the
interfaces between the plates at either end of the motor tube. It was planned to
use PVC pipe to house the propulsion assemblies. Holes were taped into both
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SADCATS
ends of the PVC pipe to allow for plates to be bolts to them. Bolt circles were
configured so that their force was distributed most efficiently across the bolts to
provide best possible sealing scenario. The equation below was used to create
the desired bolt circle.
3 < D/N*d < 6
Variable
D
d
N
Description
Diameter of bolt circle
Diameter of bolt
Number of bolts in bolt circle
By varying “N”, one can control the proximity to either 3 or 6. Numbers
closer to 3 correlate to space required for wrench clearance and numbers closer
to 6 correlate to spacing for uniformity. Since a uniform seal was our greatest
concern, our bolt circle calculations drew closer to values of 6.
Through testing, it was found that a gasket is necessary to prevent
leakage into the propulsion assemblies. Cork-rubber seals were cut to size for
both the front and back of the enclosure. Previous experimentation proved that a
torque wrench was not a suitable tool to apply torque to the bolts. Threaded
holes were stripped by trying to use a torque wrench. A stripped hole makes the
interface between the end plate and PVC wall much weaker. It was then decided
that all the bolts had to be “hand tight”. This specification is very arbitrary,
though it was needed since the PVC is much softer than bolts used for clamping
the ends of the propulsion assembly.
As a result of the arbitrary torque requirement of the bolts, the applied
gasket pressure is also arbitrary. Calculations were still completed to provide
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SADCATS
information on a how much pressure should be applied to the gasket. Applied
force to the gasket was limited due the properties of the PVC. To prevent
destruction of the PVC threads, 1/3 the magnitude of the PVC yield stress was
calculated and used as a reference for the applied force. Gasket pressure
calculations are found below.
Yield Strength of PVC = 2466 psi
Fm = (1/3) * (Yield Strength of PVC) * Area of bolts
Variable
Fm
Ag
N
Description
applied force to gasket
area of gasket
number of bolts
Gp = Fm / Ag / N
Part of the effectiveness of a bolt is the length the engagement provided
by the threads of that bolt. The pitch and diameter of the bolt determines how
much should be threaded into the mating material to be adequate. The below
equation was used to determine this specification:
Le = ( 2*At ) / .5** ( D - .64952p )
Variable
p
D
Description
screw thread pitch
nominal diameter of screw
At
tensile stress area of screw
Another aspect of important consideration for the propulsion system is the
alignment of the shaft under loading. A thrust bearing was integrated into the
design to provide linear and axial stability of the shaft while adding minimal
friction. The total length of the shaft is approximately 7 inches and would have a
tendency to wobble under loading sustained while used.
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SADCATS
The shape of the propeller required that the shaft would need a geometry
to fix the propeller in place while in motion. Initially, it was ideal to have a drive
dog be machined onto the propeller shaft. This would allow the propeller to fit
into a key way. However, the drive dog is complicated to machine, especially
with time constraints. The final idea was to fit the propeller onto the shaft by
using a split pin that had to be press-fitted into the shaft. The propeller would
then be clamped on by a washer and nut. The picture below is the final propeller
– shaft mating scenario.
INSERT PICTURE OF PROPELLER SHAFT!!!! (Figure ???)
The use of the split pin allows for a good technique to fix the propeller to
shaft. However, removing material from the shaft creates a weakness that must
be analyzed. The torque of the shaft is limited with respect to the diameter of the
pin, diameter of the mating shaft, and the shear yield strength of the shaft
material.
Tcapacity = *d2*D*Ssy / 4
Variable
d
D
Ssy
Description
pin diameter
shaft diameter
shear yield strength
Another machine characteristic of the propeller shaft is the stress
concentrated created by the narrowing of the diameter.
This is also a
weakness that would limit the strength of the material.
The below
equations state the variables that adjust for this phenomena.
Kt is the
variable that is an offset that is found by correlating D, d and r.
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SADCATS
nom = 16*T / *d3
max = Kt*nom
Variable
D
d
T
r
Description
major shaft diameter
minor shaft diameter
applied torque
radius between diameter change
It’s important to know the amount of torque that can be applied to the
shaft due to the stress concentration. Though we can also figure out what
the shaft can handle simply from material properties.
chosen because it’s a lower density material.
Aluminum was
A lower density material
would be easier to rotate through the lip seal and would require a smaller
motor to be used. A very rough estimate of the torsional yield strength can
be obtained by assuming that the tensile yield strength is between 60% and
90% of the tensile strength.
*******
5.1.4
Stability Control
The concept of stability can be seen most easily when considering what happens
when the vessel is inclined from the vertical axis due to some external moment on
the body. In equilibrium, the center of gravity of the vessel is directly above the
center of buoyancy. When an external moment is applied to the body, a heeling
moment occurs. That is to say, the vessel moves away from its state of initial
equilibrium. As long as the vessel has the properties of stable equilibrium, a
righting moment will occur after the removal of the external moment.
Along with the center of gravity, the metacenter of the vessel needs to be
considered. The metacenter is basically a pivot point and can be seen
schematically by drawing a vertical line upwards from the center of buoyancy at
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SADCATS
initial equilibrium and at some given incline. The intersection of these lines is the
metacenter. This concept can be seen in Figure 1. The usefulness of this point
can be seen in determining the stability of the craft. The goal is to have the
metacenter located above the center of gravity; this will create a stable
equilibrium. Also, the farther the center of gravity and the metacenter are from
each other the greater the righting moment is (assuming the center of gravity is
lower than the metacenter).
oM
W1
W0
L0
L1
oG
B1 o o B0
The position of the metacenter can also be determined through the use of several
equations by considering a slight inclination from the vertical. The two triangles
produced at this inclination (W0OW1 and L0OL1) must be equal in area. In figure
2, the distance y is the half-ordinate of the original waterline while the center of
gravity moves from two thirds of this value on one side of the center line to two
thirds of the half-ordinate on the other side. Therefore if the moments of volume
are considered, the resulting moment is given by:
 * 0∫L (2y3/3) dx
where 0∫L (2y3/3) dx is equal to the moment of inertia, I, of a waterplane about
its centerline. Therefore the resulting, or excess, moment is equal to IAs can
be seen in figure 2, the center of buoyancy is just the excess moment divided by
the volume of displacement.
BB1 = IQ/V
The distance BM is then equal to the inertia divided by the displaced volume.
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SADCATS
BM = I/V
The height of the metacenter can now be defined as the difference from the center
of gravity to the metacenter point.
M
y
W0
2/3y
W1
L1
2/3y
L0
y
B1
B0
K
In regards to stability of a fully submerged vessel, the concept is very similar to
that of a surface vessel. The main difference is that for a submerged vessel the
center of gravity is located below the center of buoyancy. This S.A.D.C.A.T.S.
design incorporates a ballast tank in the rear section of the hull. This will cause
the vessel to submerge tail first. With a full ballast tank the center of gravity will
have shifted from its original location to a location closer to the rear of the sub in
closer to the centerline of the sub.
5.1.5
Component Mounting System
The component mount rack was designed to accommodate all of the electronic
controls in such a way that they will be secure while the vessel is in and out of
the water. The mounting rack was designed to be of light weight and still be
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SADCATS
structurally stable while supporting the electronics. The rack comprises of three
shelves, two supporting rings, and is located in the front two sections of the hull.
PICTURES
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SADCATS
5.2 Electrical Analysis & Synthesis
5.2.1
Microcontroller Selection and Design
5.2.1.1
Selection of Microcontroller (Atmel, ATmega128)
The Atmel ATmega128 was chosen because of its computational ability,
quantity of input/output pins, and ease of programming. Of primary concern was
the ability to calculate floating point numbers, which would be useful for
calculating angles and storing sensor data. This capability was lacking in the
BASIC Stamp used in the previous generation SADCATS. The ATmega128 has
a low cost of about $5, while the BASIC stamp came as a package and cost
around $100.
In addition to its low cost, the ATmega128 consumes power at a comparable
rate to the BASIC stamp. It also contains 128kB of program memory, and 128kB
of data memory, which is useful for storing the data to be collected.
Another option investigated was the Handy Board, which has a sufficient
processor for handling the required calculations. However, since the chip itself is
only a microprocessor, an additional I/O interface would need to be designed to
handle connections to sensors and controls.
Because of this, board layout
becomes more difficult due to extra components, which also use more physical
board space than the ATmega128, which contains all needed components.
5.2.1.2
Integration with Electrical System
Since the microcontroller is required to communicate with the sensors, motors,
and other electrical devices, each needed input and output pin was designated
based on the requirements of the system.
Microcontroller pin requirements
A/D input pins
Battery Voltage Sensor #1: Any Port F pin
Battery Voltage Sensor #2: Any Port F pin
Temp Sensor: Any Port F pin
Pressure Sensor #1: Any Port F pin
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SADCATS
Pressure Sensor #2: Any Port F pin
Color Sensor: Any Port F pin
Serial I/O pins
GPS: UART 0, Port D pins 2 and 3
Modem/Radio: UART 1, Port E pins 0 and 1
General I/O pins
Turbidity/Conductivity Sensor:
Any two general purpose pins (virtual serial
connection)
Radio Tx/Rx Select: Any general purpose pin
Solenoid Valve Control: Any general purpose pin
Color Sensor Mode Control: Any two general purpose pins
Status LED: Any general purpose pin
PWM output pins
Motor #1: Port B pin 4, 5, 6, or 7
Motor #2: Port B pin 4, 5, 6, or 7
Pump: Port B pin 4, 5, 6, or 7
5.2.1.3
Organization of Program Structure
The program structure was broken into phases for purposes of a control
outline. Flowcharts and psuedocode are provided in Appendix .
A. Initialization Phase
B. Waypoint Determination Phase
C. Waypoint Seek Phase
D. Dive Cycle Phase
E. Rise Cycle/data Collection Phase
F. Transmission Phase
Steps B through F are repeated until the vehicle detects a low battery state,
upon which it enters into a phase where it will transmit its location and await
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SADCATS
retrieval.
This transmission will occur once per designated time interval
(Potentially this occurs every time a signal is read for the GPS; t=1sec).
Upon startup initialization, the vehicle will check its battery voltages and flash a
code on an LED enclosed in the clear end cap if one or both batteries are low to
alert the person deploying the craft that there is a problem. If both batteries are
okay, the vehicle will flash a continuous signal for 3 seconds. The craft will then
wait for several minutes before beginning its algorithms so that the motors and
other devices will not kick on until after it has been placed in the water. This also
gives the GPS time to initialize.
5.2.1.4
Waypoint Seek Algorithm
Since the vehicle may have a heading of any direction, the system must be
able to control the angle at which the vehicle will travel with respect to the
waypoint. The goal of this is to reduce the angle error of heading with waypoint
direction to zero. To do this, two vectors are constructed using the data from the
GPS.
First, the movement vector, of previous position to current position will be
determined, and then the error vector of current position to waypoint position will
be determined. To find the angle error, the error between these two vectors will
be calculated as follows:
 


1    
  cos  


 


Equation 5.2.1
This angle will be from 0 to 180°. In order to determine which motor should
receive less power, it is important to know whether this is a negative or positive
angle. To do this, the slope of each vector will be calculated, and the results are
as followed:
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SADCATS
Table 5.2.1
Case
True If
Angle is 0 to 180°
OR
Angle is 0 to –180°
OR
m  m AND y  0
m  m AND x  0
m  m AND y  0
m  m AND x  0
If the angle is 0 to 180°, then the craft must turn to the right to correct the angle
error, and thus the right motor will be reduced in power proportional to the angle
error plus the integral angle error. The left motor will be full power.
If the angle is 0 to -180°, then the craft must turn to the left to correct the angle
error, and thus the left motor will be reduced in power proportional to the angle
error plus the integral angle error. The right motor will be full power.
P   K p err   integral  K i err 
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Equation 5.2.2
46
SADCATS
5.2.2
Power Electronics Board
5.2.2.1
Diodes (Vishay, 1N5820)
Diodes are used on the power electronics board to prevent backflow into the
batteries so that they can be configured in parallel and have a more even drain
on their charge. This results in a larger total capacity without the need for an
array of FETs to switch between battery packs.
A parallel configuration of the packs allows for less voltage drop across the
battery when a load requires a large current draw. This is the case when the
pump is running, as it can draw up to 8A.
The chosen diodes will have a
maximum forward voltage of 0.475V, and thus the maximum power loss due to
the diodes will be at most 4% in worst case scenario.
Six diodes are used on the board with each of the six battery packs followed by
a diode.
5.2.2.2
Power FETs (Motorola, IRF540)
Power FETS are used to switch on and off the heavier load electromechanical
devices. There is one FET for each Motor, one for the Pump, and two for the
Solenoid Valve. The FETs that are connected to the motors and pump have their
gates connected to the PWM channels of the microcontroller. This allows these
devices to be run at a variable speed. The solenoid valve is connected to a FET
whose source connects to the motor battery pack, and one whose source
connects to the communications & control battery pack. This is for emergency
surfacing in case the motor pack dies while the vehicle is submerged.
The FETs were chosen to be able to handle a high continuous drain current,
due to the high current draw of the pump. The chosen FETs have a continuous
drain current rating of 19A at 100°C, with a PDS(on) of 0.07. This means that at
the worst-case scenario, there is a power loss of (.07*8A)*8A = 4.48W. This
translates to at least 95% efficiency at the worst case. Since this worst case
occurs infrequently, the nominal efficiency is much higher. For the drive motors,
the worst-case power loss is (.07*1.5A)*1.5A = .1575 watts. This is an
efficiency of better than 99%.
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5.2.3
Communications
A goal of the design team was communication of vessel location, via radio
transmission. This is essential attribute that allows vessel retrieval on a large
lake like Lake Ontario.
Additionally, transmission of vessel status and the
collected scientific data would be very useful.
Communication stretching from a base station at Rochester Institute of
Technology (RIT) to large portion of Lake Ontario is necessary so that the vessel
can maintain communication. Thankfully, an antenna at RIT can communicate
with a station on the lake almost Line-of-Sight, allowing a good range on any of
the 144-148Mhz, 222-225Mhz, and 420-450Mhz bands at low transmitting
power. Additionally, any shortcoming in the vessel’s antenna can be mitigated by
the selection of the base station antenna at RIT, where a significantly larger and
more suitable antenna design can be utilized.
5.2.3.1
Modem and Radio Transceiver (Chipcon SmartRF CC1000)
A modem is needed to take data, such as serial GPS data, and modulate it into
frequency information. A radio is needed to move the modulated signal to the
appropriate frequency range.
Two possibilities were given serious consideration, a simpler pricier solution and
a more complex but cheaper and more compact solution. The simple solution
was to use the Maxim modem chip used by last year’s team, and connect the
chip to an amateur radio band transceiver, which is a handheld size device.
Most handheld transceivers offer 5 Watts output power, and often have a lowpower output mode.
The more complex option, is use of the Chipcon CC1000, an IC that performs
both modem and transceiver functions in one chip. The chip’s output power is
10dbm, or 10mW, thus use of the chip would require an amplifier module to step
up the chip transmit output. A Tx/Rx switch to toggle the amplifier in and out of
the circuit is also required. However, this combination of parts is cheaper and is
a slightly more compact space-wise. The CC1000 is confined to a range of 300
to 1000Mhz, which means the vessel would need to transmit on the 440Mhz
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SADCATS
band.
Another useful feature is of the CC1000 is the programmable output
power, selectable from –20dBm to 10dBm in 1dDm increments. This allows fine
control over output power.
5.2.3.5
Radio Amplifier, and Tx/Rx switch
(Mitsubishi, RA07H4047M, Ramsey RFS1 Kit)
The radio amplifier chosen is a compact four-pin module that is capable of 10W
output for 10mW input, which is the capability of the Chipcon CC1000.
5.2.3.6
GPS (Garmin GPS-35)
The GPS chosen by the team is a module that has no interface aside from a
serial connection. This allows the vessel to travel to data points, and allows the
user to locate the vessel for retrieval. The GPS has an absolute accuracy of 15
meters, but relative accuracy is much better, usually less than a meter.
A
WAAS-capable GPS with an accuracy of less than 3 meters was considered, but
it was found the client had no need for the increased absolute accuracy.
The GPS supplies the Microcontroller with positional data once every second,
and this allows re-calculation of speed and heading once a second.
5.2.3.7
Antenna
The antenna of the craft must be tuned for the 440Mhz band, be omnidirectional, and be unobtrusive enough to not affect vessel drag and stability. A
¼-wave single element antenna measuring approximately 7” is chosen by the
team, because it requires only one puncture of the hull and creates little drag.
The antenna could be cut from a standard car antenna, as that would provide
flexibility and ensure that the antenna does not break off during user handling.
The antenna could also be used as a mount for a florescent orange flag,
enhancing the vessel’s visibility. A longer ½-wave type antenna could be used if
the longer length did not create handling problems for the user deploying the
vessel.
5.2.3.5
Data flow, error detection and error correction
A few possibilities for increasing the reliability of transmission are still being
considered by the team at the time of this report. A simple strategy would be to
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SADCATS
send transmit ASCII-encoded data to the base station, and wait for an ACK, a
keying of the receiving station indicating it acknowledges the signal. An addition
to this, Hamming Coding or some other method can be used to provide some
data redundancy and allow one-way error detection and correction.
5.2.3.7
Legal Restrictions
The FCC Code of Federal Regulations Title 47, Volume 5, Part 97, Section
97.301. grants use of the 144-148Mhz, 222-225Mhz, and 420-450Mhz bands,
among others, to license-holding amateur radio operators, known as “Hams” (see
Figure 5.2.4.1)
One of the team members, Matthew Stith, is a licensed
technician-class amateur radio operator, as is Dr. Kremems of the College of
Imaging Science. While the vessel is under a control of a licensed Ham, the
FCC part 97 rules allows the vessel to transmit and receive data on the allotted
frequency bands provided the Ham has licensed access to those frequency
bands.
Figure 5.2.4.1
5.2.4
Data Acquisition and Sensory Package
5.2.4.1
Pressure Sensor (SenSym ICT, 19C-100P-A-6-K)
In order to ensure an accurate measure of depth, various pressure sensors
were examined in order to provide a large range of pressures, a high degree of
linearity, and easy integration with the microcontroller.
Since the maximum
required dive depth was set to be 100 feet, which is roughly 58psia, a sensor was
selected to go well beyond this range.
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SADCATS
The sensor selected provides a reading of 1mV/psi, with a maximum zero
pressure offset of ±2mV, but typically has no offset. The operating range (fullscale span) of the sensor is 0-100psi, with ±0.1% pressure nonlinearity. The
effect on this reading by temperature is only a maximum 0.5% of the full-scale
span, so this sensor will be relatively accurate. It receives power from a 12V
connection.
In order to receive input from the sensor through an A/D channel on the
microcontroller, the voltage will be scaled from 0 to 3V in order to account for a
possible unexpected pressure surges. Since the A/D channel is 10 bits wide, the
resolution of the pressure will be .163psi/level, or 6.135 levels/psi. In order to
accomplish this task, an amplifier will be constructed using an op-amp circuit.
5.2.4.2
Temperature Sensor (Analog Devices, AD592CN)
Since temperature was an important quantity to measure, the temperature
sensor was selected to provide accurate, linear measurement. The range of
operation was selected from 0°C to roughly 32°C. The sensor itself has a total
range of -25˚C to 105˚C. The temperature sensor receives power from a 5V
connection.
The AD592CN has a temperature coefficient of 298.2μA/°C. This is scaled
using a voltage dividing circuit and calibrated to then output 10mV/K. Since the
range of input of interest is 273.2K to 305.2K, this would mean that the output
would need to be shifted by 2.73V in order to set 0°C as the 0V point. Since the
range is now 32K, or.32V, this is scaled to correspond with the 5V limit of the A/D
channel. A difference amplifier implemented using an op-amp circuit performs
the scaling and shifting.
As configured, analysis of the difference amplifier results in the following
equation:
Vout  Vsensor  Vbias 
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R2
R1
Equation 5.2.3
51
SADCATS
In order to scale 0.32V to 5V, we select R2/R1 = 5V/0.32V, or about 15.625.
Here, a higher gain would result in a lower maximum temperature, and if this max
temperature is set to 82°F, a gain of 18 could be used. This shift of the sensor
output, results in .03125°C/level, or 32 levels/°C.
5.2.4.3
Turbidity/Conductivity Sensor (Honeywell, APMS-10G)
Turbidity and Conductivity of the water were also useful quantities to measure,
and thus a sensor with dual capability was chosen in order to make the sensor
interfacing simpler. This turbidity sensor uses a serial port connection to the
microcontroller, and collects data when a request signal is transmitted to it. It
receives power from a 12V connection, but is compatible with a varying input
from 8V to 30V.
Turbidity is a measure of the degree to which light traveling through a water
column is scattered by suspended particles in the water and is measured in
Nephelometric Turbidity Units (NTU). The selected sensor can measure turbidity
from 0 to 4000 NTU, with a maximum response time of 1.3 seconds.
Electrical conductivity is measured in mSiemens, with a range of .0001 to 15.
The response time for said measurement is .85 seconds.
Since the turbidity/conductivity sensor interfaces with the controller through a
serial port connection, no extra circuitry is needed to scale or shift the signal.
Data is collected when an activation signal is transmitted to the sensor.
5.2.4.4
Color Sensor (Taos, TCS230)
The color sensor is used to detect the intensity of light in the water from each
color component of light. It is designed to measure red, blue, green, and white
light intensities and output the data as frequency. A module made by parallax
will be used to interface the Taos color sensor with the microcontroller through an
A/D channel. The color sensor receives power from a 5V connection.
The module allows the frequency range to be scaled down to a range that the
microcontroller can detect, and must be put in a separate mode to detect each
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SADCATS
color’s intensities. In order to do this, four output pins will be needed to set the
scaling and the mode.
For the scaling, the pins on the board can be directly tied to VDC or GND,
depending on the scaling that is needed. The two mode control pins will be
controlled by two general purpose I/O pins on the microcontroller.
5.2.7
Power Sources
The battery design is required to be a secondary type, rechargeable, battery, as
primary batteries require frequent replacement, and thus would make the vessel
very expensive to operate.
Furthermore, it is much easier to recharge the
batteries in place than to open the entire hull every time batteries needed to be
replaced. However, when secondary batteries are used in an application that
requires reliability, care must be used to ensure that any battery failure during, or
at the onset, of vessel operation is properly sensed and reported to the user.
5.2.5.1
Selection of battery chemistry
The team rapidly realized during the design phase that compared to the first
generation SADCATS, power consumption would be much greater, because the
second generation vessel is to be propelled with electric motors where the first
generation vessel is un-powered. In addition to this, the new vessel also needs
to be much lighter than its predecessor, perhaps even light enough for handdeployment. Naturally, the conclusion is that batteries with higher energy density
would help meet these two design goals.
Therefore, the most desirable battery chemistry for the project would offer high
gravimetric and volumetric energy density.
On top of that, a chemistry that
requires simple power management circuitry allows for many charge/recharge
cycles, and is easily available at a reasonable cost.
Of the many possible
chemistries available, discussion here within is limited to the three biggest
contenders: Lead-Acid, Nickel Metal-Hydride, and Lithium Ion.
Lead acid was the chemistry choice of the Generation One SACATS project
team. Lead-Acid batteries are available for a low cost, and are available in a
wide variety of capacities (per cell), making power delivery simple.
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This
SADCATS
chemistry is also very resistant to overcharging, which simplifies charging of the
cells. Additionally, Lead-Acid cells can be found in a large range of capacities,
simplifying the construction of a battery pack that has a large energy density.
However, the gravimetric energy density, 30 to 50 Watt Hours/Kilogram, is poor
compared to the other contenders.
Lead-acid cells are not desirable for
applications in which a battery is deep discharged, as this damages the cells and
shortens the number of charge/discharge cycles of the battery before failure.
Lithium-Ion is a much newer battery technology that allows for very good
gravimetric energy density at 110 to 160 Watt Hours/Kilogram, and excellent
volumetric energy density. However, Lithium-Ion cells are very expensive per
Watt hour, and the Lithium-Ion cells are sensitive to overcharging and
discharging at too high a rate, requiring more complex electronics for power
management to prevent damage. Lithium-Ion cells are not commonly available
in large capacities, meaning that a large-capacity pack requires many cells.
Nickel-Metal Hydride (NiMH) chemistry has been chosen, mainly because of its
high gravimetric energy density, ranging from 60 to 120 Watt Hours/Kilogram.
This chemistry carries a significant price premium over Lead-Acid, but the
increased energy density gives tangible improvements to the weight of the
vessel, making deployment easier, decreasing hull material costs, and
decreasing drag through the water. NiMH cells are not commonly available in
capacities exceeding 9 Watt hours per cell, and the most dense NiMH cells are
typical in the area of 5 Watt hours per cell. This means that a large capacity
pack requires a high quantity of cells, but a large number of smaller cells
provides more options for battery positioning inside the hull.
5.2.5.2
Determination of Battery Capacity/ Configuration
A power budget was constructed to compare different battery pack
configurations, and to find a solution that provides enough capacity to meet the
target mission length of 16 hours. A good portion of the duty cycle data is a bestguess estimate, and this means that in action, the vessel could use power at a
different rate than shown. It is preferable to partition the cells into packs such
that an incorrect estimation of the motor's rate of power use would not cause one
pack to discharge a long time before another pack. It is also be ideal to provide a
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SADCATS
way for the microcontroller board, GPS, and radio to remain active even if the
power allotted to the drive motors, dive pump and solenoid valve has been used.
Thus it was decided that two packs are to be used, a high capacity pack for large
current devices, such as the motors, pump, and solenoid valve, and a smaller
capacity pack for everything else, including the Microcontroller, GPS, and Radio.
This configuration has the added benefit of protecting the Controller Board from
the voltage fluctuations caused by switching high current devices on and off.
Table 5.2.2 Vessel Power Budget
Part
Voltage
Temp
Current,
Wattage,
Current,
Wattage,
Duty
Effective
inactive (mA)
inactive (W)
active (mA
active (W)
cycle
(W)
5
0
0
.300
.002
10%
.000
12
00
0
1.500
.018
10%
.002
12
0.007
0
2.000
.024
10%
.002
Opamps
12
0
0
2.000
.024
100%
.024
Modem
3
8
.024
10.00
.030
1%
.024
12
0
0
32.00
.384
10%
.038
uContorller
5
12
.06
20.00
.100
100%
.100
Radio
12
0
0
1000
12.00
1%
.120
GPS
5
20
.1
120.0
.600
90%
.550
Solenoid
12
0
0
1220
14.64
5%
.732
Pump
12
0
0
8000
96.00
2%
1.920
Motors
12
0
0
3000
36.00
50%
18.00
sensor
Press
sensor
Color
sensor
chip
Turbidity
sensor
valve
All parts
21.57
Pump,
20.65
motors,
solenoid
valve
All
other
0.837
parts
Based on the Power Budget spreadsheet, it is determined that the Motor Pack
have a capacity of around 300Wh, and the Communications Pack should have a
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SADCATS
capacity of around 20Wh to ensure long communications lifetime and increase
reliability.
Table 5.2.3 Battery Capacity Options
Pack 1 battery Pack 2 battery Travel/Dive life Communication life
capacity (Wh) capacity (Wh) (hours)
(hours)
Option 1
Option 2
108
216
Option 3
Option 4 (lead-acid)
324
288
21.6
5.23
10.46
23.72
15.69
13.95
Table 5.2.4 Battery Capacity Options
cell
pack
Weight Weight Weight price
Volume
cell type/
capacity capacity number price/cell per Cell per Pack per Pack per
(in^3) (as
chemistry voltage (mAh)
(Wh)
of cells ($)
(gram) (gram) (lbs)
pack ($) a block)
pack 1, option 1 4/3A NiMH
pack 1, option 2 4/3A NiMH
1.2
1.2
4500
4500
108
216
20
40
5.75
5.75
62
62
1240
2480
2.728
5.456
115
230
27.3
54.7
pack 1, option 3 4/3A NiMH
pack 1, option 4 Lead Acid
1.2
6
4500
12000
324
288
60
4
5.75
21.8
62
3720
8.184
15.72
345
87.2
82
184.7
pack 2, option 1 AA NiMH
pack 2, option 2 Lead Acid
1.2
12
1800
2300
21.6
27.6
10
1
2.00
12.5
28
280
.616
2.05
20
15
22.4
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5.2.5.3
Power Management
A key problem the team encountered in building a high capacity NiMH pack is
that capacity must be increased without paralleling cells, which can lead to
discharging problems that shorten the life of the cells.
One solution given a lot of consideration was the use of a higher voltage than
the standard 12 Volt DC system. For instance, a 36V system would allow for
triple the pack capacity than compared with a 12Volt system using the same cells
in each case. 36V motors should, theoretically, be lighter than a 12V version for
the same power output, because lighter gauge wire can be used for the windings,
though in practice the team did not see this advantage while looking for parts.
Moreover, pumps, motors, and solenoid valves are generally more available at
12V. 12V components could still be used, but a high current switching regulator
would be needed to convert from 36V to 12V, adding to the expense and
complexity of the power electronics board and creating a 20% worst-case power
loss through the regulator. Still, even if suitable 36V components could be found,
the Power Budget shows that the resultant 36V pack would probably still not
have the capacity needed, and some sort of other provision (paralleling,
separating packs) would be needed to get a high enough capacity.
A simpler method involves putting diodes in series with each pack, which allows
packs to be paralleled without any discharge problems. The drawback is that
there is a power loss due to the voltage drop across the diode, and high current
devices exacerbate this problem. The efficiency for this method could be better
than 95% if the right diodes were chosen, and this convinced the team to go with
the diode solution.
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5.2.5.4 Battery Voltage Sensing, Power Redundancy, Power Switching
Sending a sample of each pack’s voltage to two ADC inputs on the Atmega128
allows the battery pack voltages to be monitored.
This in turn allows the
microcontroller to ensure that the vessel does not initiate a dive when the Motor
pack is depleted. In addition, two power FET's are connected the solenoid valve
to allow vessel surfacing using power from the Communications Pack even if the
Motor Pack is depleted to the point that its voltage is insufficient to actuate the
valve. In this case the vessel is able to make a final surfacing and enter Battery
Fail Mode.
5.2.6
Electromechanical Devices
5.2.6.1
Motors
The motors operate for a large portion of the duration of the mission. For this
reason, motors with a relatively low current draw are desirable, so as to not drain
the capacity of the batteries. From calculations of the power needed to push the
vehicle thorough the water at a desirable speed, it was determined that motors
should have an input power between 15 and 20W.
Since the motors are
powered by a 12V connection, the motors should nominally draw 1.25A to1.67A
each.
Using the power budgeting calculations, and that power range, the
vehicle’s motor pack will last from 14 to 18 hours.
Further analysis was conducted in order to find the ideal motor for this
application. The motors will need to put out between 6oz-in to 12-oz-in of torque.
There are no specific size limitations due to the fact that a casing for the motors
has not been developed as of yet.
Refer to Appendix (xx) for calculations
regarding the actual amount of torque needed for the motors.
5.2.6.2
Pump
As the determination of the battery chemistry was made prior to pump
selection, electrically importance was thus placed on the requirement that the
pump use a rate of power that the batteries could support. The chosen pump
draws 8A maximum, which translates to 1.33A per battery if the batteries are
connected in parallel. This amperage will cause little voltage drop within the
battery when configured in this fashion, since batteries of NiMH composition
have relatively low internal resistance.
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5.2.6.3
Solenoid Valve
Two types of solenoid valve were investigated; normally open and normally
closed. The normally open valves were desirable in the case of battery failure
underwater. If the batteries fail, the valve would open and the vehicle would
surface.
However, since investigation determined that normally open valves
require higher current to close than normally closed valves would require to
open, a software failsafe was designed in order to allow the a normally closed
valve to operate if the motor pack were to be depleted.
A normally open valve would require power to remain closed during the enter
dive phase, and when stopping to collect data. However, a normally closed valve
would only require power when it needs to be opened to rise. As such, the
normally open solenoid valve would be active for longer amounts of time, further
decreasing battery life.
The selected valve is normally closed and draws .33A when closed.
5.2.7
Lighting
The intent of navigation lights for the vessel is to provide compliance to the
United States Coast Guard boating regulations. Aside from regulatory concern, it
was important for recreational boaters to be able to distinguish the difference
between the vessel and the water surface.
The total vessel length is less than 48 inches and thus the Coast Guard
Regulations designate motor-powered vessels under 12 feet in length to have a
light on the bow with a green and red light. Each light on the bow must be visible
from 120-degrees. There is also a requirement for a stern light which is white.
The white light must be visible for 360-degrees. The driving principle of the
lighting configuration is to allow for nocturnal boaters to decipher the direction of
waterway traffic. The table below correlates the direction of travel with the light
that is visible from the boat.
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Table 5.1.X
Lighting Visible
Direction of Travel for Vessel
white light
green light and white light
red light and white light
red and green light
away from observer
right
left
toward observer
Another variable that had to be considered was the estimated speed of the
vessel. The group planned the speed of the vessel with respect to the maximum
foreseeable current it would experience on Lake Ontario during typically weather
patterns. As the max current was estimated to be one-half of a knot, the design
team planned the vessel to have surface mobility at a speed of 1 knot, which
translates to 1.15 mph.
It was determined that the U.S. law was questionable on the point of lighting for
a powered autonomous craft. The SADCATS project vessel does not fit the
United States Coast Guard's definition of a “vessel”, because it is autonomous.
On the other hand, the team's vessel is not just a buoy, as buoys are defined as
moored or drifting, while the SADCATS vessel is powered.
The U.S. Coast
Guard Inland Navigation Rules are not clear on the requirements for such a
vessel and no clarification was given when the Coast Guard was contacted.
The design team attempted to find components to achieve the United States
Coast Guard boating regulations. Mounting lights on the outer surface of the
vessel was not a feasible option and available lighting did not meet the pressure
specifications that would be needed for diving to 100ft. Lights mounted on the
outside of the vessel would also create more drag.
The vessel is predicted to have a mission length of 16 hours and thus could be
deployed at the beginning of the day and retrieved in the evening. Therefore its
operational period would typically take place in daylight.
Nevertheless, if the vessel is to run between sunset and sunrise, it must have
some lighting, even if it is lighted as if it was a drifting buoy. Installation of a mast
head light on the exterior of the vessel was found to be problematic for the
mechanical design due to stability, sealing, and drag concerns. The team has
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decided instead to opt for a daytime mission profile, so that the vessel will not
require lighting, but will instead feature a florescent orange flag on the antenna
mast and the hull will be outfitted for high visibility. The design will be kept
flexible to allow possible future installation of a buoy caution light on the exterior
of the vessel, or the installation of a 180-degree visible blinking light inside the
transparent front hemisphere of the craft.
When the group weighed all the factors, it was talked about to put a white light
in the hemisphere section of the sub. Since the sub will run day missions, it is
not critical for it to have a white light. A white LED during the day doesn’t serve a
great deal of purpose. By containing the light inside the sub, it would not be
subjected to external pressures caused by the water depth. The hemisphere will
be made of plexiglass which is transparent. The light would be visible from
inside the hull. During the course of our information search, a correlation was
found to relate candle power of an LED with a distance of visibility. The LED(s)
we have picked provide for a visibility of up to 6 nautical miles.
Table XXX (refer to reference XXX
Range of visibility
Minimum luminous
(luminous range) of light in
intensity of light in
nautical miles
candelas for K = 0.81
1
0.9
2
4.3
3
12
4
27
5
52
6
94
However, at this point in time we do not know how well the plexiglass will allow
light to pass through. Testing would need to be done following assembly to be
sure of the visibility distance provided by the LED(s) from inside the hull.
Another possible implementation to make the sub more visible is to apply
reflective tape to the cylindrical sections of the hull. This would make the sub
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highly visible during daylight hours or in the proximity of other the navigation
lights of other vessels.
5.3
Analytical Conclusion
The design of the electrical systems allow the vessel to make accurate scientific
measurements more easily than the present “bucket” practice. The craft is able to
navigate to waypoints autonomously via utilization of GPS telemetry and
transmission of acquired data to base station for analysis.
Power redundancy decreases the chance of losing the vessel to sea or to the
bottom of a lake. A system status LED alerts the user to any error conditions prior
to deployment, and verifies proper operating status.
Power management is
efficient and the battery has proper capacity to complete the misson.
There are some unresolved issues, however. Integrity of the transmitted data
must be ensured either by uni-directional or bi-directional error detection and
correction protocols. Additionally, a copy of the data should be logged locally so
that it can be downloaded after the vessel is retrieved. Motors and propellers also
need to be determined. Calculations have been made that can determine the
correct motor and the correct propeller.
As of now, the team is waiting for a
response from the motor vender on what the most suitable motor will be for our
situation. After that is taken care of, propellers can be sized accordingly.
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6.0 Status and Outlook
With the conclusion of the Preliminary Design Phase of the Sr. Design Project,
the SADCATS group now looks forward to the transition from the design phase to
the fabrication and testing phase.
6.1
Obtainment of Components and Materials
Purchase requests have been turned in for all of the components and materials.
The bill of materials can be found in section 6.4 under Budget. As for the motors and
propellers, exact models are still to be determined. Their respective prices and vendors
have been left out for the time being.
6.2
Fabrication
The fabrication of the frustrum and hemisphere for the hull of the sub is to be
made by Quickturn modeling. The cylinder section will be fabricated by the team.
The rest of the construction, including the integration of the electrical components
will be completed in the next ten weeks.
The microcontroller board schematic is being jointly developed under Dr.
Kremens, the sponsor. The board layout, board manufacture, and component
stuffing will be performed by FSI systems, Farmington NY.
6.3
Testing and Calibration
6.3.1 Temperature Sensor Calibration
The temperature circuit will be calibrated to provide 10mV/K before
amplification and shifting. This should be done using a potentiometer to calibrate
the circuit with the proper resistance value. Since the range of interest is from 0°C
to 32°C, the circuit will be shifted by some bias voltage which will be
provided using a calibrate voltage divider that uses a potentiometer.
6.3.2 Pressure Sensor Testing and Calibration
The zero point offset of the pressure sensor will be measured by measuring the
atmospheric voltage compared to a known current value and interpolating the data
back to the zero to measure the offset. If the offset is non-zero, it will be
compensated via software.
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6.3.3 Dive and Surfacing System Testing
Testing the dive system will be accomplished by setting the software to only
include the dive system. The vehicle will be placed in a deep swimming pool or
other large body of contained water. A short dive depth will be specified in order to
determine whether the system can properly dive and surface in a body of water in
which it can easily be retrieved should the system fail to either dive or rise.
6.3.4 Locomotion Control Testing
The craft will be tested on an open body of water in order to determine if the craft
will adequately be controlled on the surface. Starting from a random bearing, the
craft will be required to accurately seek the waypoint within a minimum error
distance to be determined. This test will be performed independently of the dive
and surface phases of the code.
6.4
Budget
The budget for SADCATS is shown below.
Bill of Materials
Item
Part Name
Ballast System
Part
Number
9171K22
Material
Vendor
Brass
9171K214
Brass
9802K4
Brass
44555K132
Brass
7876K11
8063K37
Delrin /
nitrile
Brass
7768K16
Brass
7768K22
Brass
Tubing
5394K16
Hose
Clamps
Dromedary
Bag
Dromedary
54195K14
Nitrile /
Nylon
Stainless
Steel
Cordura
Nylon
Plastic
McMasterCarr
McMasterCarr
McMasterCarr
McMasterCarr
McMasterCarr
McMasterCarr
McMasterCarr
McMasterCarr
McMasterCarr
McMasterCarr
Campmor
Pipe Fitting
Inline
Strainer
Tube Fitting
Solenoid
Valve
Air Tank
Valve
Check
Valve
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REI
Quantity
Price ($)
Line Price ($)
2
7.09
14.18
3
1.84
5.52
1
11.58
11.58
3
1.38
4.14
1
34.38
34.38
2
2.80
5.60
1
8.17
8.17
1
8.17
8.17
10
.92
9.20
1
4.47
4.47
1
24.95
24.95
1
10.00
10.00
SADCATS
Bag Cap
Pump
Electromechanical
Hull
Mechanical
Miscellaneous
61957
Motor
Cylinder
48855K52
Frustrum
Hemisphere
ABS block
Plexiglass
block
Supports
8747K128
Propeller
Teflon Tape
4591K12
O-rings
9557K201
PVC
ABS
Plexiglass
PVC
PTFE
Teflon
EPDM
Advanced
Auto
Faulhaber
1
McMasterCarr
Quickturn
Quickturn
Quickturn
Quickturn
1
63.60
63.60
6
3
1
1
45.00
45.00
TBD
TBD
270.00
135.00
TBD
TBD
McMasterCarr
1
18.08
18.08
2
1
1.59
TBD
1.59
2
6.67
13.34
McMasterCarr
McMasterCarr
154.14
2
154.14
TBD
Estimated Cost = $796.11
The electric components will be covered
under the College of Imaging Science
Electrical
Power
Amplifier
Batteries
GPS
Temp
Sensor
Color
sensor kit
Diode
MOSFET
Relay kit
RA07H404
7M
MhDBA170
0TAB
GPS35HVS
28138
RFparts.co
m
Thomas
1
19.75
19.75
10
2.65
26.50
Purchased
by sponsor
Parallax
1
0.00
0.00
1
9.00
9.00
30054
Parallax
1
79.00
79.00
177973
210518
RFS1
Jameco
Jameco
Ramesy
Electonics
10
10
1
.73
.25
19.95
7.30
2.50
19.95
Estimated Cost = $164.00
6.5
Project Completion Timeline
The project completion timeline can be found overleaf.
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6.6 Unresolved issues
6.6.1 Mechanical
6.6.1.1 Motors
Although calculations have been made in order to select motors for the vessel,
the vendor is in the process of selecting the best motor for the mechanical and
electrical requirements.
6.6.1.2 Propellers
In order to select the propellers, the motor selection is needed first. The
dimensions of the propellers can somewhat make up for a lack of torque from the
motor.
6.6.2 Electrical
6.6.2.1 Recharging Cables
Among the electrical issues still remaining is the issue of recharging the
batteries. Currently there is no simple way to recharge the cells. While it would be
possible to remove the end cap and access a charging cable in that manner, this is
hardly ideal. Possible solutions include a watertight plug that could allow access to
the charging apparatus, or some sort of inductive charger. Currently there is no
way to bring out a charging cable, however charging equipment has been
obtained.
6.6.2.2 Power Switch
Also undressed is a method of powering on and off the craft. Similar to the issue
of recharging methods, it would be beneficial to have some external means of
switching the power on and off. Possible methods include a sealed plug that would
be attached to the wires connected to the power switch. The power switch could
be fastened to the underside of the plug. If it were difficult to fasten wires to a plug,
they should be easily accessible using a pair of tongs or my reaching in with a
hand.
6.6.2.3 Software Revisions
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It had been desirable to be able to reprogram the microcontroller via radio,
however since the ATmega128 receives code through a JTAG interface, this is
no longer possible. Concurrent with the power switch and recharging
mechanisms it would be desirable to have a means of revising software without
removing the end cap.
6.6.2.4 Control System Parameters
Due to lengthy mechanical systems analysis, there had been insufficient time
to simulation and design for the exact control system parameters. A PI controller
had been designated for locomotive control on the surface, while simple on/off
control methods had been specified for the controlling the pump and solenoid
valve. The next step is to develop a working simulation in which the control
system parameters can be designed and developed by integrating the
mechanical design equations into a MatLab simulation alongside a model of the
control system.
6.6.2.5 Waypoint Determination
A method of waypoint determination is currently undecided. Some possibilities
are for the craft to use its initial position as the first waypoint, and calculate other
waypoints relative to that location. The waypoints may spiral outward from the
initial position, move in a zigzag pattern from west to east, or any other scheme
that would allow for a suitable grid of data to be collected.
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7.0 Conclusion
The presented design provides a solution that will be invaluable to the client. The vessel
is much lighter weight, has horizontal locomotion ability, and also boasts the addition of
turbidity, conductivity, and water color sensing. The second generation design still
retains the features of the first generation vessel, namely diving ability and GPS
awareness.
There have been some bottlenecks in the design. The first priority of the electrical
designers will be to finalize the microcontroller board schematic allow prompt testing of
sensors and programming. The mechanical designers will acquire the motors and
propellers to allow fabrication of the motor housing.
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References
American Society of Mechanical Engineers. ASME Boiler and Pressure Vessel Code An
American National Standard: Section X Fiber-Reinforced Plastic Pressure Vessels.
1989 ed. New York: ASME, 1989.
Buchmann, Isidor. Batteries in a Portable World. 2nd ed. New York: McGraw-Hill,
2001.
Coast Guard Boat Crew Seamanship Manual. Stability. Chapter 9. 29 Oct. 2003.
Faulring, Jason. Personal Interviews. Sep.-Nov. 2003
Federal Communications Comission. Code of Federal Regulations Title 47. Volume 5.
Part 97. Section 97.301. 30 October 2003.
<http://www.w5yi.org/Part97BCD.htm#Sec.%2097.301>
Fox, Robert W., and Alan T. McDonald. Introduction to Fluid Mechanics. 5th ed. New
York: John Wiley & Sons, Inc., 2000.
Gieck, Kurt, and Reiner Gieck. Engineering Formulas. 7th ed. New York: McGraw-Hill,
1997.
Incropera, Frank P., and David P. Dewitt. Fundamentals of Heat and Mass Transfer.
5th ed. New York: Wiley, 2002.
Kozak, Dr. Jeffery. Personal Interviews. Sep.-Nov. 2003
Kremens, Dr. Robert. Personal Interviews. Sep.-Nov. 2003
Lewis, Edward V. ed. Priciples of Naval Architecture: Resistance, Propulsion, and
Vibration. Jersey City: The Society of Naval Architects and Marine Engineers, 1988.
Lewis, Edward V. ed. Priciples of Naval Architecture: Stability and Control. Jersey City:
The Society of Naval Architects and Marine Engineers, 1988.
MatWeb Online Material Properties Database. 6 Nov. 2003 and 11 Nov. 2003.
<http://www.matweb.com>
Megyesy, Eugene F. Pressure Vessel Handbook. 11th ed. Tulsa: Pressure Vessel
Publishing, 1998.
Muckle, W. ed. Naval Architecture for Marine Engineers. England: Newnes –
Butterworths, 1975.
Pagliarulo, Todd. Personal Interview. 24 Oct. 2003.
Papoulias, Dr. Fotis A. Ship Hydrostatics. 27 Oct. 2003.
<http://web.nps.navy.mil/~me/tsse/NavArchWeb/1/toc.htm>
Uhl, Steven. Phone and Email Correspondence. Oct.-Nov. 2003.
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United States Department of Transportation. United States Cost Guard Navigational
Rules: International-Inland. Washington D.C.: US Governetment Printing Office,
1999.
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Appendix
A.1
A.2
A.3
A.4
Initial Concept Development Ideas
Weighting of Criteria for Analysis
Concept Feasibility Voting Results
B
Psuedocode for Controller
B.1
B.2
B.3
B.4
B.5
B.6
Psuedocode for Initialization Phase
Psuedocode for Waypoint Seek Phase
Psuedocode for Dive Cycle Phase
Psuedocode for Rise Cycle
Psuedocode for Data Transmission
Psuedocode for Battery Fail
C
Flow Chart for Controller
C.0
C.1
C.2
C.3
C.4
C.5
C.6
Flow Chart of Entire System
Flow Chart for Initialization Phase
Flow Chart for Waypoint Seek Phase
Flow Chart for Dive Cycle Phase
Flow Chart for Rise Cycle
Flow Chart for Data Transmission
Flow Chart for Battery Fail
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A.1
Initial Concept Development Ideas
01.
02.
03.
04.
05.
06.
07.
08.
09.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
106761095
Gas powered boat
Sailing surface vehicle
Buoy that takes measurements
Submersible with electric motors
Pontoon boat
Solar Buoy
Solar Boat
Surface vehicle with sensors on a tether
Submersible with snorkel to transmit data
Dynamic diver
Static diver
Hybrid diver
Drifter without powered directional control
Open frame submersible
Closed frame submersible
Surface vehicle with electric motors
Cluster of transmitting and receiving pods
Electric surface vessel with programmed diving
Closed frame boat
Drifter powered by solar cells
72
SADCATS
Capability
Power Consumption
Communications
Serviceabiltiy
Package
Life Span
Part Availability
Difficulty
Cost
Reliability
Adaptability
Weighting of Criteria for Analysis
Weight
A.2
Weights
Weight
5
0.07576
Cost
3
0.04545
Reliability
7.5
0.14394
Adaptability
2.5
0.06818
Difficulty
2.5
0.06818
Part Availability
2.5
0.09091
Life Span
1.5
0.05303
Package
1
0.06061
Serviceability
1
0.05303
Communications
2
0.15152
0.5
0.07576
0
0.11364
Power Consumption
Capability
0
0
2
2
2
3.5
2
3
2.5
8
4.5
7.5
1.00000
Favors Row
Split Decision
Favors Column
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A.3
Concept Feasibility Voting Results
Pugh's Method with Weighted Scale
Base Model: Electric Surface Vessel
Weight
Cost
Reliability
Adaptability
Difficulty
Part Availability
Life Span
Package
Serviceability
Communications
Power Consumption
Capability
Comparative Score
Electric
Submersible
1
2
3
4
1
3
2
4
2
3
2
5
2.84091
Solar
Surface
3
2
3
2
2
3
3
2
3
3
4
3
2.83333
Weights
0.07576
0.04545
0.14394
0.06818
0.06818
0.09091
0.05303
0.06061
0.05303
0.15152
0.07576
0.11364
1.00000
A score of 3 is equal to base line, with 5 best, 1 worst
A.4
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B
Psuedocode for Controller
B.1
Psuedocode for Initialization Phase
Psuedocode for Initialization Phase
read: battery voltage from the motor pack (A/D, Port F)
read: battery voltage from the communication pack (A/D, Port F)
if (motor pack voltage too low OR communications pack too low)
while (vehicle is on)
if (motor pack voltage is too low)
flash: red LED for 3 flashes (General I/O Pin)
pause
end
if (communications pack voltage is too low)
flash: red LED for 2 flashes (General I/O Pin)
pause
end
end
/* All systems go */
set: integral error to zero
flash: red LED continuous for 3 seconds
delay: 3 minutes until exiting initialization
check: if GPS has initialized properly (General I/O Pin, Virtual Serial)
while (GPS not initialized)
NOP
end
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B.2
Psuedocode for Waypoint Seek Phase (Perform algorithm every sec)
check: if GPS has initialized properly (General I/O Pin, Virtual Serial)
while (GPS not initialized)
NOP
end
read: GPS string from I/O pin (virtual serial, port).
fetch: current position, (x,y) from the GPS string
Δx=xcurrent-xprevious
Δy=ycurrent-yprevious
xerr=xwaypoint-xcurrent
yerr=ywaypoint-ycurrent
θerr=(Δx*xerr+Δy*yerr)/( (Δx2+Δy2)1/2 *(xerr2+yerr2)1/2 )
mΔ=Δy/Δx
merr=yerr/xerr
PE = Kp*θerr
/* Kp is %/˚ */
if [ (|mΔ|>|merr|) AND Δy>0 ] OR [ (|mΔ|<|merr|) AND Δx<0 ]
/*Means angle is 0 to 180˚*/
IE = Ki*θerr+IE
Left motor gets 100%
Right motor gets 100% - (PE+IE)
else
/*Means angle is 0 to -180˚*/
IE = Ki*-θerr+IE
Right motor gets 100%
Left motor gets 100% - (PE+IE)
end
if (left motor power less than minimum motor power)
set: left motor power to minimum power
end
if (right motor power less than minimum motor power)
set: right motor power to minimum power
end
set: left motor PWM to the set percentage (Port B, one of [7..4])
set: right motor PWM to the set percentage (Port B, one of [7..4])
save: current position, (x,y) to memory for next waypoint seek calculation
read: battery voltage from the motor pack (A/D, Port F)
if (battery voltage is too low)
call: the battery fail function
end
Δs=(xerr2+yerr2)1/2
if (Δs < Δsmin)
/* Sub is within range of waypoint*/
set: left motor PWM: 0% (Port B, one of [7..4])
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set: right motor PWM: 0% (Port B, one of [7..4])
set: integral error to zero
end
B.3
Psuedocode for Dive Cycle Phase (Loop performs every sample
interval)
Apply Voltage to pump
read: pressure from sensor (A/D, Port F)
while (pressure < Pmax)
read: battery voltage from the motor pack (A/D, Port F)
if (battery voltage is too low)
turn off pump
do
open solenoid valve (General I/O Pin)
while( not on surface)
call: the battery fail function
end
read: pressure from sensor (A/D, Port F)
end
read: pressure sensor (A/D, Port F)
while (below depth for first data point)
open solenoid valve (General I/O Pin)
end
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B.4
Psuedocode for Rise Cycle (Loop performs every sample interval)
next data point depth = 100ft
while (depth > 1 ft)
save: coordinates
read: pressure (A/D, Port F)
save: depth/pressure
read: temperature (A/D, Port F)
save: temperature
send: data request to turbitidy sensor (General I/O Pin)
read: turbidity (General I/O Pin)
read: conductivity (General I/O Pin)
save: turbidity
save: conductivity
set: color sensor: red mode (2 General I/O Pin)
read: red intensity (A/D, Port F)
set: color sensor: blue mode (2 General I/O Pin)
read: blue intensity (A/D, Port F)
set: color sensor: green mode (2 General I/O Pin)
read: green intensity (A/D, Port F)
set: color sensor: white mode (2 General I/O Pin)
read: white intensity (A/D, Port F)
read: battery voltage from the motor pack (A/D, Port F)
if (battery voltage is too low)
switch solenoid valve to controller battery pack
do
open solenoid valve (General I/O Pin)
while( not on surface)
call: the battery fail function
end
while (depth < depth for next data point)
open solenoid valve (General I/O Pin)
read: pressure (A/D, Port F)
end
next data point depth = current data point depth + 1ft
end
open solenoid valve (General I/O Pin) /*empty ballast*/
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SADCATS
B.5
Psuedocode for Data Transmission
enable: transmit (General I/O Pin)
while (Δt < .1sec)
NOOP
end
transmit: data (tx serial, UART 1, Port D)
while (Δt < Δtmax)
read: rx serial, UART 1, Port D
if (transmission acknowledged)
return
end
NOOP
end
enable: transmit (General I/O Pin)
while (Δt < .1sec)
NOOP
end
transmit: data (tx serial, UART 1, Port D)
while (Δt < Δtmax)
read: rx serial, UART 1, Port D
if (transmission acknowledged)
return
end
NOOP
end
save: transmission not ack’d status
B.6
Psuedocode for Battery Fail (repeats every second)
while (vehicle has power)
read: GPS (General I/O Pin, Virtual Serial)
fetch: coordinates from GPS string
enable: transmit
while (Δt < .1sec)
NOOP
end
transmit: location (tx serial)
end
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SADCATS
C
Flow Chart for Controller
C.0
Flow Chart of Entire System
Start
Initialization
Phase
Waypoint
Determination
Phase
Waypoint
Seek Phase
Battery Fail
Process
Dive Phase
Rise Phase
Data
Transmission
Phase
C.1
Flow Chart for Initialization Phase
Start
Read Motor and
Communication
Pack Voltages
No
Is either
voltage low?
Yes
Set Integral Error
to Zero
Flash LED
continuously for 3
seconds
No
Is motor pack
voltage low?
Yes
Flash LED 3 times
Delay 3 Minutes
Pause
No
GPS
Initialized?
Yes
No
Is comm. pack
voltage low?
Yes
Flash LED 2 times
End
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Pause
80
SADCATS
C.2
Flow Chart for Waypoint Seek Phase
No
θerr > 0
Yes
Right Motor Power
= 100%
Left Motor Power =
100%
Left Motor Power =
100%(Kpθerr+IE+Kiθerr)
Right Motor Power
= 100%(Kpθerr+IE+Kiθerr)
Save Current
Coordinates
No
No
No
Any Motor
Power < min?
Yes That motor Power
= min
Motor Pack
Voltage low?
Yes
Δs < Δsmin?
Battery Fail
Chart
Yes
Set both Motor
Power to zero
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SADCATS
C.3
Flow Chart for Dive Cycle Phase
Start
Apply Voltage to
Pump
No
Is Motor Pack
Voltage low?
Yes
Turn Off Pump
Open Solenoid
Read Pressure
No
Open Solenoid
No
Is Pressure >
Pmax?
Yes
No
Is pressure
within εp of Pmax
?
Yes
Yes
On Surface?
Battery Fail
Chart
End
C.4
Flow Chart for Rise Cycle
Start
Collect and Save
Data
No
Is Motor Pack
Voltage low?
Switch Solenoid
Valve to
Communications
Pack
Yes
Open Solenoid
Valve
Open Solenoid
Read Pressure
No
No
Within 0.5ft of
surface?
Yes
On Surface?
Battery Fail
Chart
Yes
Open Solenoid
Valve
No
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Within εp of
next data point
pressure?
End
Yes
82
SADCATS
C.5
Flow Chart for Data Transmission
Start
Transmit Data
No
Acknowledged
?
Yes
No
Has Δt
passed?
Yes
Retransmit Data
No
Acknowledged
?
Yes
No
Has Δt
passed?
Yes
Save
Transmission not
Acknowledged
Status
End
C.6
Flow Chart for Battery Fail
Start
Read GPS
Transmit Location
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SADCATS
D
Results of Finite Element Analysis
D.1
Displacement Due to 165 (Expected +30)psi Internal Ballast System Load
D.2
Von Mises Stress Due to 165 (Expected +30)psi Internal Ballast System Load
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SADCATS
D.3
Strain Due to 90 (Expected +30)psi External Vessel
D.4
Von Mises Stress Due to 90 (Expected +30)psi External Vessel Load
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SADCATS
D.5
Displacement Due to Maximum External and Internal Pressure Loads
D.6
Von Mises Stress Due to Maximum External and Internal Pressure Loads
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SADCATS
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SADCATS