Duke University, Pratt School of Engineering
Department of Mechanical Engineering and Materials Science
Autonomous Underwater Vehicle Mechanical Design
ME160
Dr. Robert Kielb
Spring 2008
Advisor: Marc S. Verdiel
Mark Peterson
Brandon Guard
Andrew Camacho
Brayden Glad
David Klein
Abstract
The goal of this project was to design and fabricate
multiple components to be utilized in an Autonomous
Underwater Vehicle (AUV). It is our intent that with the
help of other members of the Duke Robotics Club from the
ECE/CS departments the AUV will compete in San Diego
at the end of July. The scope of the project included the
chassis, mechanical claw, and marker dropper. It was our
aim to improve the previous designs of the chassis and
marker dropper and the mechanical claw was incorporated
as a new task for the upcoming competition. The tasks that
must be completed during the competition involve both
vision as well as acoustic software in concert with a durable
mechanical structure. A layout of the testing pool is shown
in Appendix 5.
Problem Definition - Chassis
Purpose
The AUV competition has been attended by the Duke Robotics club for the last
eight years. Along the way, three vehicles have been designed and manufactured. The
chassis that was used most recently is still fully functional and only requires the
replacement of a couple cards on the computer stack. However, the cylindrical shape of
the electronics housing on the previous model did not lend itself to the installation of the
newly acquired Doppler Velocity Log (DVL). The DVL is a key component of the AUV
providing it with the ability to move in an x-, y-, z-coordinate system once a point of
origin is established in the water. The top AUVs in the competition are getting lighter
and smaller so reducing the weight of the vehicle was also important. Past chassis
designs used a larger, heavier DVL so incorporating the new DVL was crucial in our
decision to build a new chassis.
Current Standard
The goal of this project is not to produce an AUV that is up to the industry
standard since most of these vehicles are designed by the military or large engineering
firms and are far beyond the scope of any undergraduate project. The current standards
that our design team is basing the project off of are the previous AUVs built by the Duke
Robotics Club as well as the other top competition from schools like The University of
Florida (UF) and École de Technologie Supérieure (ETS). A CAD of the previous year’s
vehicle can be seen below:
Figure 1: CAD of previous AUV
Expert Consultation
For the AUV, most of the expert consultation was received from the professional
machinists. One of the things that must be understood when going into a design project
involving components that must be water tight is the difference between the ability to
design and the ability to fabricate that component. Past vehicles had made use of
cylindrical plastic tubes which were easily made water tight using a plastic weld and/or
an end cap sealed with o-rings. The new chassis would be rectangular in shape so it was
necessary to consult with Don Pearce from the medical machine shop to determine how
this could be accomplished.
Preliminary Design Work - Chassis
Product Design Specifications
The physical requirements of the chassis are that it remains water tight up to
approximately two atmospheres of pressure (approximately 30 ft), it must avoid
entangling with the external environment of the testing pool, it must be able to operate in
chlorinated and saline water, it must fit in a 1.83x0.91x0.91 meter box, and it must be at
least 5% positively buoyant. It is also a goal that the overall weight of the vehicle be
minimized from the previous year’s model which weighed 36 kg.
Quality Function Deployment (QFD)
The QFD performed on the chassis can be viewed in Appendix two. The
information gathered from this calculation was vital in determining the shape of the
chassis that will be housing the computer, DVL, and various other electronics. The three
shapes that were compared in the QFD were a rectangular box design, the cylindrical
electronics tube used last year, and the flooded parabolic shell design that had been
employed in the AUV from two years ago. Some of the key parameters were the relative
shape of the components stored inside the chassis to the chassis itself. Since most of
these components are rectangular in shape, optimal space usage would favor the
rectangular chassis. Also of importance was the weight of the vehicle. The competition
disqualifies all vehicles weighing over 50 kg and gives a bonus to those vehicles that
weigh less than 38 kg. Thus, a design that optimizes the volume of the chassis is ideal.
Given that we have already noted the rectangular shape provides optimal packing, the
rectangular chassis is again favored. The last parameter that is important to mention is
the ease by which the new lightweight DVL can be attached. The cylindrical shell does
not offer a conceivable solution to this problem nor does the parabolic shell design.
Design Decision
Given the results found in the QFD exercise, it was determined that the
rectangular chassis design would be optimal for the continuing improvements that have
been made to the AUV project in the last few years. The chassis will be less bulky and
more lightweight with the incorporation of the new DVL and the increased space
efficiency. Further additions will need to be made to the chassis to improve the
hydrodynamics of the AUV however this is beyond the scope of this design project.
System Modeling - Chassis
Stability and Buoyancy Calculations
One of the most important calculations required for the AUV is the buoyancy and
stability of the vehicle. In order to determine these two values, an excel spreadsheet was
first set up that determined the total weight and buoyancy of each component being
attached to the chassis. The results of this can be seen below. A buoyancy force of zero
indicates that a component is located inside the chassis and therefore is already being
accounted for in the total buoyancy of the chassis.
Table 1: Totaled Weight and Buoyancy for Chassis Assembly
By performing these calculations it was possible to determine the total weight as well as
the net buoyancy of the vehicle. Given that the dry weight of the vehicle at the
competition last year was 36 kg, the new chassis design has stripped approximately 6.5
kg off of the previous model. Also, there is a net buoyancy force of 6.25 N ensuring that
the AUV will return to the surface if there happened to be a loss of power.
In order to perform the stability calculations for the AUV in terms of the pitch and roll
degrees of freedom, an (x,y) origin was set at the center point of the bottom plate as seen
in the drawing below. The +Y axis runs vertically upward and the +X axis runs
horizontally to the right from the origin. After determining the center of mass for each
individual component and multiplying that by the weight of the component, the total Xand Y-moments can calculated. Next, by dividing the moments by the total weight of the
vehicle the X and Y center of mass for the AUV is found. Considering the origin is at the
center of the base plate, X and Y center of mass values close to zero will ensure the
vehicle’s stability with respect to pitch and roll.
Figure 2: Top View of Chassis Assembly
Table 2: X- and Y- center of mass for chassis assembly
The stability of an underwater vessel is also determined by the relative locations
of the center of mass and the center of buoyancy in the Z-direction. Another spreadsheet
was used to determine these values with the origin set at the top of the base plate as seen
below. The +Z axis runs vertically upward and the +Y runs horizontally to the left from
the origin.
:
Figure 3: Front View of Chassis Assembly
Table 3: Z-center of mass and Z-center of buoyancy
The calculations show that the Z-center of mass is approximately 3.2 inches
below the Z-center of buoyancy. This ensures that the AUV remains stable and is not
prone to rolling.
Finite Element Analysis
A fluid dynamics analysis using Solidworks FloWorks was conducted on the
entire chassis, using a gliding (motors off) velocity of 1 m/s forward in water. As is
visible from the table below, the pressure change over the body is negligible at this speed,
which represents more than the maximum velocity of the vehicle. The maximum
pressure increase is about 2 kPa, and the wake area generates a pressure drop of a further
7 kPa. From the images, recirculation effects are noticeable but are apparently minor.
Table 4 Minimum and Maximum Values for Chassis gliding at 1 m/s in water
Figure 4: Velocity Profile: A front view demonstrates the effect of the forward-facing fins in forcing
fluid over the top of the craft.
Velocity Profile: A side view illustrates the flow over the claw assembly and along a
thruster.
Prototype Construction
Because the tolerances involved in fabricating a water tight vessel are so small,
our design team found it necessary to have the chassis machined by a professional
machinist. Features of the chassis include two view ports machined from polycarbonate,
a hole through which the DVL is mounted and made water tight, flanges that run along
the base plate as well as the front face of the chassis to which external components are
mounted, and a top plate that will be latched to the sides of the chassis using nonlocking
screw latches allowing the tension in the clamp to be regulated. An image of this
mechanism is shown below:
Figure 5: Nonlocking Latch From mcmaster.com
Aluminum was chosen as the material used for the exterior of the chassis because of its
durability and light weight. Other than the low tolerances required for an underwater
vessel, it is also difficult to weld aluminum thus providing us with another reason to have
the chassis machined professionally. There was an unforeseeable delay in the completion
of the chassis so it will be necessary to complete the assembly over the summer.
Problem Definition – Marker Dropper
Purpose
As stated in the AUVSI and ONR’s 11th International Autonomous and
Underwater Vehicle Competition, one of the challenges that the AUV must complete is to
place a marker within a 12” by 24” box (See Figure 1). There are four possible target bins
that the markers can be dropped into, but only two markers may be dropped during the
competition. Each bin will have a different point value associated with it, depending on
its color or another distinguishing characteristic.1
Figure 6 - Marker Box Diagram
1
http://www.auvsi.org/competitions/PreliminaryMissionStatementfor2008AUVCompetition.pdf
The competition rules further state that the marker must fit within a 1.5” by 1.5”
by 6” box and weigh no more than 1.5 pounds while in air. Each marker must bear the
team name or marking to be differentiated from the other markers that may be in the
target bin. Any marker that exceeds these limits by less than 10% will incur a significant
point penalty, while any marker that exceeds the limits by 10% will be disqualified.2
Current Solution
Last year’s AUV was equipped with a single marker dropper system. It operated
through use of a permanent magnet that would be jolted with a pulse of electricity to
release a metal ball from its attractive power. This mechanism affected the AUV’s
positioning sensor.
It weighed approximately one kilogram and the solid steel ball used as a marker
weighed approximately 20 grams.
Proposed Solution
The new competition rules meant that the old marker dropper could not fulfill all
the requirements necessary to receive full points in the contest. The proposed solution not
only improves accuracy and precision over last year’s model, but also contains sufficient
room for additional markers if needed in future competitions.
In the new marker dropper, a cartridge with six holes for markers, 60o apart, is
rotated by a stepper motor that turns 7.5o each pulse. Each step rotates the marker
cartridge towards a stationary hole in the base of the marker dropper, with eight steps
needed to go from one hole to the next. Once the cartridge hole is over the stationary
hole, the marker in the cartridge hole will fall through and travel through the water and
land in the target bin.
2
http://www.auvsi.org/competitions/PreliminaryMissionStatementfor2008AUVCompetition.pdf
This solution should weigh less than the previous model due to the lighter
materials needed for this proposed design.
Information Gathered – Marker Dropper
Existing Products
While there are few, if any marker droppers that have been designed with the
specific needs that the International Autonomous and Underwater Vehicle Competition
have set out, there are many products out on the market that drop material to a central
point or area. Examples include gumball machines and vending machines. However, for
this ME 160, project, these products would not efficiently fulfill the contest regulations.
Figure 7 - Gumball Machine and Vending Machine34
A design based on either a gumball machine or a vending machine would have the
advantage of being able to hold many markers. However, a gumball machine does not
pack gumballs in an organized or efficient manner that this competition demands. Also, a
gumball seems to work best with spherical markers, whose path through water can be
hard to predict. A vending machine packs its internal products in a very ordered manner,
but its drop point is very irregular, which leads to poor accuracy.
3
4
http://www.crobike.de/en/werbemittel_bilder/promopeddler/9300/20050.jpg
http://www.usvendingking.com/images/Img20.jpg
More applicable and practical existing products are ones that focus primarily on
accuracy and precision. A very recognizable example of this currently on the market is
the revolver. Every bullet is shot from the same position in a repeatable motion. A
revolver also loads the bullets in a very ordered and efficient manner.
Figure 8 – Revolver5
Preliminary Design Work- Marker Dropper
Product Design Specifications (PDS)
In order to conform to the rules set out by the International Autonomous and
Underwater Vehicle Competition, as well as to try and be as efficient as possible in
design, some overall goals were established.
Performance Goals:
The marker dropper must drop at least two markers in a simple, repeatable
motion; however, if the dropper can release more than two markers, it is more
advantageous. The markers must be dropped from the same point each time to maximize
accuracy.
Physical Requirements:
In accordance with the International Autonomous and Underwater Vehicle
Competition rules, the markers must be able to a 1.5” by 1.5” by 6” box and weigh no
5
http://julia.hanovercomputer.com/press%20release/gun/10-05/postpress%2010.05/images/57412.jpg
more than 1.5 pounds. The marker dropper should also be neutrally buoyant and small, so
that it can be placed anywhere on the AUV.
The marker dropper must also be waterproof to at least 20 meters and must
function for a minimum period that will last for the entire contest (approximately 10
hours). However, a long lifetime, of four years is preferred.
Quality Function Deployment
The QFD is a tool used to compare customer requirements with the engineering
characteristics of a design. Results from this tool are used to weigh the importance of
consumer concerns and how they are correlated to considered design elements. In the
QFD used for the marker dropper, the design options included: a circle of compartments
which turn (six-shooter); spiral rotation flips a catch (vending machine); spring action
loads next round (pistol clip). These three designs were compared using the following
criteria: ability to drop different sized markers; ability to drop multiple markers; weight;
size; cost; style; hydrodynamics. Correlations between the design options were weighted
on a -3, -1, 0, 1, 3 scale (-3=terrible, -1=weak, 0=average, 1=good, 3=excellent).
The six-shooter design focuses on rotating a hole to each marker, allowing it to
fall through the hole towards the target bin. Depending on its construction, it could
handle many different sizes and numbers of markers, but once built, it would be difficult
to change the design to accommodate a change in marker design. It would be cheap and
lightweight depending on the materials used, but would probably not look very nice and
would not be very hydrodynamic.
The vending machine-inspired design would contain a rotating screw that would
flip a catch at specific intervals to drop the marker into the water. This seemed very
difficult to create and while very versatile, the difficulty in creating it outweighed any
advantages it might have.
The pistol design would have a clip of markers that would be pushed out one by
one from behind by a piston. The next marker would move into place immediately due to
a spring that would be pushing all the markers towards the opening. This design could
hold a large amount of markers, but the size and shape of the marker would be limited.
The QFD results show that the simpler design of the six-shooter pushed it over the
pistol clip design, as it would be easier to control a stepper motor rotating a hole from
place to place over a piston pushing a marker through a hole. The uncertainty of how a
marker would perform under the compressing stress of a piston also made a gravityinduced fall more preferable.
Figure 9 - Preliminary Design
Theory of Inventive Problem Solving (TRIZ)
TRIZ was developed in 1946 by Genrich Altschuller as a method for generating
solutions to problems involving engineering contradictions. Altschuller catalogued 39
different engineering characteristics as well as 40 inventive principles that have been
used to solve these contradictions between these characteristics. For the marker dropper,
the contradictions looked at using TRIZ were how to improve the reliability (#27) of the
drop point in the marker dropper without increasing the complexity of the device (#36).
TRIZ suggested three inventive principles to solve this dilemma: #35 Parameter
changes; #1 Segmentation; and #13 The other way round. Parameter changes were not
looked into because neither phase nor state changes would improve reliability without
increasing device complexity. Segmentation was not used since it was also not very
practical either due to the already very simple nature of a rotating cartridge and base and
therefore could not easily be divided into more parts.
TRIZ third principle, #13 the other way around, was very useful for the marker
dropper design. It suggested to make moveable parts (or the external environment) fixed
and make the fixed parts moveable. This lead to a design change of making the base plate
fixed and having the stepper motor rotate the marker cartridge instead. Not only did this
make the design thinner, but it also made the marker dropper simpler as well. Fixing the
base plate also allowed for a fixed drop point, which increased the accuracy of the
dropper, as it is easier to program the AUV to center on a single, unmoving point instead
of a point that rotated depending on the number of the dropper the device was rotating
towards.
Design Decision
Using the results from both the QFD and TRIZ, the final design of the marker
dropper began to come together.
Figure 10 - Final Marker Dropper Design
There would be six areas for markers to be placed in the dropper cartridge, even
though only two would be used for this year’s competition. This way if later competitions
increased the number of allowable markers, the current dropper would already be able to
accommodate this change in the rules.
The cartridge would be rotated by a stepper motor, which in turn would be
controlled by the main computer in the AUV. This would allow the AUV to hover over
the target bin, rotate the marker cartridge until the next marker dropped through the fixed
hole in the base-plate and then move on to the next point in the competition.
Since the stepper motor is not waterproofed, a segmented tube was designed in
which the top partition would be waterproof and the bottom would be flooded with water.
This is easier to create that attempting to make the entire marker dropper waterproofed
because the holes in the cartridge where the markers sit would allow water to flood into
the compartment whenever it aligned with the stationary hole in the base-plate. The top
section of the tube would be waterproofed from above with the aid of O-rings and from
the bottom by epoxy and waterproof sealants.
Where the stepper motor shaft needed to come in contact with the cartridge there
would be a seal of Vaseline encased in a copper tube. The shaft would go through the
Vaseline and then be epoxied to the cartridge. The combination of pressure exerted by the
stepper motor on the Vaseline and surface tension of the Vaseline would keep the top of
the tube water tight.
The base-plate would be epoxied to the outside of the tube so that it was flush
with the bottom of the cartridge. In order to ensure that the stepper motor would be able
to rotate the markers in the cartridge to the stationary hole in the base-plate the plate
would be aligned with the cartridge so that the hole in the plate is on top of a hole in the
cartridge.
Materials
Several different material types were used in the construction of the dropper due
to different requirements and considerations. The casing of the dropper itself was made
out of clear polycarbonate. This material had the advantage of being strong, light, and
transparent. This last characteristic was very important because it was essential to have
good visibility within the body of the dropper such that everything could be lined up
appropriately during assembly. It was also essential to be transparent so that the operators
of the AUV would know if the upper compartment of the dropper had flooded, thus
signaling that the stepper motor would be not functional and in need of replacement.
The six-cartridge shooter was constructed by the 3-D printer and therefore was
made out of ABS plastic. This was advantageous for two reasons. Firstly, the slots within
the cartridge had to be constructed exactly in place with very little deviation. This is
because the stepper motor works in exact 7.5 degree increments, so if the cartridge were
not built exactly to specification then stepper motor would misalign the cartridge and the
exit hole thereby preventing the markers from dropping. Because of this, it was more
sensible to use the 3-d printer to build the cartridge exactly to specification than
attempting to bore the holes manually (more likely to result in error and misalignment).
Another major advantage of the ABS plastic is its weight. The only resistance force that
the stepper motor faces when trying to rotate the cartridge is the normal force between
the cartridge and the exit plate. By using ABS plastic, we are reducing this resistance
force to zero when the cartridge is submerged in water as a result of buoyancy forces. It
was for these reasons that using ABS plastic and the 3D printer was the most practical
approach to creating the cartridge.
For the top sealing cap and the bottom guiding cap, aluminum was chosen as the
most appropriate material. Aluminum was an appropriate material for two reasons. First,
its relatively heavy weight helped us to offset the buoyancy force from the dry
compartment in the dropper. So by choosing aluminum we were able to stay closer to
neutral buoyancy than had we chosen a plastic. Aluminum was also beneficial due to its
machinability and strength. For the top sealing cap in particular, it had to be machined on
the lathe with very tight tolerances, especially with regard to the o-ring slots. Aluminum
provided the rigidity and strength required to machine these features into the cap.
Markers
In order to improve accuracy, it was decided that streamlined torpedo like
markers would be used instead of the standard metal ball that was used previously. See
the following figure for a schematic of the markers.
Using COSMOSFloworks in Solidworks, the pressure distribution with respect to
velocity was determined in order to figure out the net forces acting on the marker at a
particular speed. The pressure distributions came out as one would expect with higher
stagnation pressures at the front and low pressures acting on the back surface, thus
resulting in drag. See the following figures for the results:
The calculation process to determine the terminal velocity of the markers required
iteration. A reasonable velocity was used as the input into the program and the resulting
drag force was determined. If the drag force was too high or too low, the velocity was
adjusted until a net force of zero was observed acting on the object, thus signaling the
terminal velocity of the marker. See the following calculations:
F d=
A=
1
ρ v 2Cd A
2
π 0.4
4
2
= 0.1257 in2 = 8.1 x (10)-5 m 2
Volume of Marker = 4.88 * 10-6 m3
ρ=1000 kg/m 3
Mass of Displaced Fluid = 0.00488 kg
Buoyancy Force = F b = 0.0479 N
Mass of Marker = .00756 kg
Weight of Marker = .0742 N
Drag force (F d ) required for terminal velocity = 0.0263 N
Velocity (where F d = 0.0263) = 1.41 m/s
Cd =
Re=
2Fd
ρ v2 A
= 0.327
ρ νl
= 14,000
μ
As can be seen the above analysis, the final terminal velocity for the marker came out to
be 1.41 m/s. This speed also corresponded to a drag coefficient (Cd) of 0.327. Looking at
reference material on the subject, it was found that the Cd for a bullet is only 0.295.6 Thus
the computational results from COSMOSFloworks seemed reasonable.
Testing
Because there are no sensors with regard to the positioning of the dropper
cartridge, the most important thing is that cartridge holes are always at the position that
the computer thinks they are in. To test this, we simply activated the stepper motor and
looked to see whether every 8 activations (60/7.5) a cartridge hole was aligned with the
bottom guiding hole. During our testing, the cartridge and the guiding hole were always
6
6
http://www.aerodyn.org/Drag/tables.html
aligned when they should have been, and thus we determined that dropper should
function predictably during the course when only one revolution of the dropper cartridge
is required.
We always tested markers’ ability to fall accurately. Both standard ball bearings
without the torpedo attachment and our markers were dropped in roughly 1 meter tall
large test tubes. While the ball bearings continuously swirled around randomly and
interfered with the test tube walls, our markers fell straight down in a stable fashion as a
result of the stabilizer fins.
Lastly, the dropper was submerged in a bucket of water for a few minutes in order
to determine whether or not the upper compartment stayed dry. There appeared to be no
moisture within the upper compartment and therefore we concluded that the stepper
motor should remain dry and operational during the length of the course.
Conclusions
Future Project Directions
Following the work that was completed over the course of this semester,
continued design and testing will be undertaken during the summer in preparation for the
contest at the end of July. One of the largest problems with this project has been the lack
of underclassmen involvement. However, it is the goal of the internships during the
summer to get around four or five new members involved and acquainted with the AUV
project. There is still another working chassis from last year that could also be repaired
and improved. Thus, the goal for the summer is to come away with two working chassis
designs.
Thanks for the help during the semester:
- Dr. Kielb
- Marc Verdiel
- Pat Maguire
-
Milan Simonovic
Don Pearce
John Goodfellow
Joe Owen
Appendix 1: Product Design Specification
Product Design Specification: AUV Marker Dropper
Brayden Glad
Mark Peterson
Andrew Camacho
Brandon Guard
David Klein
27 January 2008
Function: Design a device capable of dropping multiple markers accurately in an
underwater setting. The markers will be dropped into bins with different patterns and
colors on the border of the bins. Using vision software, the AUV will identify the target
bins and release the markers accordingly.
Client Requirements:
• Waterproof to at least 20m
• Markers must be dropped into bins with the opening of the bins having
dimensions 12”x24” with a 6” border around each.
• Attachable so that robot will fit in a 1.83x0.91x0.91m box.
• Markers must fit into a box 1.5”x1.5”x6” and can weigh no more than 1.5 lbs –
exceeding these requirements by less than 10% will incur a significant penalty
and by more than 10% will result in disqualification.
1. Physical and Operational Characteristics
a. Performance Requirements: Must be accurate enough to drop the markers
consistently into a 12”x24” opening. To ensure this, the marker should
not deviate further than two inches from the point directly below the
release point of the marker when the AUV is one meter above the bin.
b. Safety: Must not prevent the robot’s ability to be recovered in the event of
power loss or entanglement (the vehicle must be positively buoyant by no
less than 0.5% of its weight). Must avoid entangling with environment
whenever possible. Must not impede transport.
c. Power: Must operate on at most 1.5 A of 24V DC.
d. Lifetime: The marker dropper must be useable for the contests (~10 hours
in pool/year) and testing (~100 hours in pool/year) for a period of 4 years.
e. Operating Environment: Non-distilled water pool, possibly saline or
chlorinated. Head may be up to 20m.
f. Transport: Cannot impede either sling carriage or manual lifting.
g. Size: Markers must fit in a box 1.5”x1.5”x6”
h. Weight: Each reduction of 1 kg is worth approximately 1/450 the value of
completing the task, and 1/45 of the value of finishing in one minute less
time. The markers must be less than 0.68kg and there will be at least two
markers in use during competition. The previous markers weighed
approximately 20 grams and the dropper weighed about 1 kg. In order to
push towards a more lightweight design, the marker dropper assembly
should weigh less than 1 kg.
i. Style: Must be elegant in construction, as befits the world-class institution
that Duke Robotics is.
j. Buoyancy: Object need not be neutrally buoyant, but robot as a whole must
rise to surface after loss of power. See also safety.
k. New or Special Features: The previous design incorporated a permanent
magnet to release the markers. This affected the positioning sensor on the
AUV so it is our goal to incorporate a different release mechanism. The
new design will make use of a revolver design and thus eliminate the
necessity of permanent magnets.
2. Production Characteristics
a. Quantity: A single model for use on the actual competing robot. It is
beneficial for product to be attachable to new chasses.
b. Target Product Cost: Less than $300.
3. Miscellaneous
Resilience: Should be flexible enough in design to adapt to future challenges.
Product Design Specification: Chassis
Function: Design a water tight vessel capable of storing all electrical components of an
AUV while ensuring that the space inside the vessel is utilized in an efficient manner.
The vessel must be easily opened, durable, and lighter than the previous year’s prototype.
The vessel is to be used in an AUV competition at the end of July 2008.
Client Requirements:
• Waterproof to at least 20m
• Must fit in a 1.83x0.91x0.91m box.
• Must weigh less than 50 kg or else vehicle is disqualified. Any vehicles less
than 38 kg will receive a bonus for being under weight.
1. Physical and Operational Characteristics
a. Performance Requirements: Must be durable and reliable to prevent
flooding of electronics
b. Safety: Must avoid entangling with environment whenever possible. Must
not impede transport.
c. Power: Propelled through the water using 6 tecnadyne thrusters
d. Lifetime: The chassis must be useable for the contests (~10 hours in
pool/year) and testing (~100 hours in pool/year) for a period of 4 years.
e. Operating Environment: Non-distilled water pool, possibly saline or
chlorinated. Head may be up to 20m.
f. Transport: Cannot impede either sling carriage or manual lifting.
g. Size: Must fit in a 1.83x0.91x0.91m box.
h. Weight: Must weigh less than 50 kg or else vehicle is disqualified. Any
vehicles less than 38 kg will receive a bonus for being under weight.
i. Style: Must be elegant in construction, as befits the world-class institution
that Duke Robotics is.
j. Buoyancy: Must be slightly positively buoyant to ensure that the vehicle
floats to the surface in the case of power loss.
k. New or Special Features: Rectangular shape to mount new lightweight
DVL and allow for better use of space.
2. Production Characteristics
a. Quantity: A single model for use on the actual competing robot. It is
beneficial for product to be attachable to new chasses.
b. Target Product Cost: approximately $2000.
3. Miscellaneous
Resilience: Should be flexible enough in design to adapt to future challenges.
Appendix 2: QFD
Chassis Options
Parameter
Ease of seal
shape of internal
components relative to
shape of chassis
strength of material
ease of opening
Weight
Size
Hydrodynamics
Style
Cost
Ability to Mount new DVL
Weight
3
Rectangular
0
Cylindrical
1
parabolic
shells
0
0
3
0
5
4
4
5
2
2
2
1
4
3
1
3
3
0
-1
0
0
3
1
0
3
1
0
3
1
1
-1
1
0
-1
0
0
-1
3
1
-1
15
4
12
15
0
-2
0
0
12
5
0
12
5
0
6
2
1
-4
5
0
-4
0
0
-2
6
1
-4
56
30
AUV
design
used in
previous
year's
competition
2
AUV
design
used in
competition
two years
ago
Weighted Total
Please put a 3 (excellent
for this design
characteristic), 1 (good),
0 (average), -1 (weak), -3
(terrible) into each box,
and the spreadsheet will
calculate your results.
Appendix 3: Budget
Marker Dropper Budget
Exterior
Comments
Tubing
Epoxy
19.45
0
Aluminium Top/Base Plate
O-Rings
43.33
0
62.78
Exterior Total
Interior
Stepper Motor
Divider
Copper Tube
Epoxy
0
0
0
0
Purchased on McMaster
Carr
Found in Machine Shop
Purchased on McMaster
Carr
Found in Machine Shop
Donated by ECE
Department
Found in Machine Shop
Found in Machine Shop
Found in Machine Shop
Sealant
Cartridge
Markers
Ball Bearings
Interior Total
Extras
0
0
0
4.42
4.42
Plastics
19.29
O-Rings
14
33.29
Extras Total
Marker Dropper
Total
Purchased on McMaster
Carr
Purchased on McMaster
Carr
100.49
Chassis Budget
Aluminum Welding
Comments
Inclusive Cost
Total
Chassis Total
Found in Machine Shop
Rapid Prototyper
Rapid Prototyper
Purchased on McMaster
Carr
2000
2000
2000
Appendix 4: Gantt Chart
Send to Medical Center
Appendix 5: Competition Test Pool Layout