Triton
T
n Offs
shore
e Dev
vice:
A new
w solution for subse
ea geote
echnical in
nvestigattion
Fiinal De
esign R
Report
Maay 8, 20144
Sub
bmitted to:
Michael L.
L Petersonn, Ph.D.
In partia
al fulfillmeent of requiirements foor MEE 4888, Spring 2014
CC:
Murray Callaway,
C
M.A.
In partia
al fulfillmeent of requirements fo
for ECP 4888, Spring 22014
bmitted byy:
Sub
Tho
omas Allainn
Pau
ul Amsdenn
Etthan Gray
Brad
dy Jacquess
Eriik Medina
Matthew Storgaaard
Mattheew Waldrooup
Abstract
Subsea geological investigations are important to the development and progression of
offshore structures including natural resource and alternative energy exploitation. Current
research techniques involve surface-based procedures which are expensive and ineffective. The
goal of this undergraduate project, in collaboration with The Ryan Beaumont Corporation, is to
develop a more efficient process to acquire information on seafloor and riverbed composition.
This report includes the parameters and solutions, as well as the process and theory,
behind every detail that is integrated into the design. The full-scale device is designed to house
and transport geotechnical equipment to the seafloor to perform rock and soil investigations. The
structure’s frame is able to withstand and counteract any forces or vibrations created by the
testing equipment. By utilizing ballast pods and a control system, the stability of the platform is
monitored during ascension and descension maneuvers. The autonomous control system allows
the structure to determine its current orientation and make any necessary adjustments.
A prototype model was constructed to represent the physical properties of the device
including size, weight, and performance criteria. Various stability experiments were performed
on the prototype, the procedures and results of these tests are also included in this report.
Contributions
Thomas Allain:
 Design Concept Process (Ballast), Recommendations for Future Designs, Website
Paul Amsden:
 Purpose, Overall Design Description, Design Concept Process (Frame)
Ethan Gray:
 Design Concept Process (Stability & Controls), Conclusions
Brady Jacques [Lead Writer]:
 Scope, Design Concept Process (Stability & Controls), Design Testing & Evaluation,
Recommendations for Future Designs
Erik Medina:
 Design Concept Process (Frame), Project Poster
Matthew Storgaard:
 Design Concept Process (Stability & Controls), Website
Matthew Waldroup:
 Abstract, Design Concept Process (Ballast)
Table of Contents:
1 2 3 Introduction ............................................................................................................................. 1 1.1 Purpose .......................................................................................................................................... 1 1.2 Scope of Full-Scale Model Design ............................................................................................... 2 1.3 Scope of Prototype Design ............................................................................................................ 2 Overall Design Description ..................................................................................................... 3 2.1 Frame ............................................................................................................................................ 3 2.2 Ballast Tanks ................................................................................................................................. 4 2.3 Air System .................................................................................................................................... 4 2.4 Control System .............................................................................................................................. 4 Design Concept Process .......................................................................................................... 5 3.1 Overview ....................................................................................................................................... 5 3.2 Full-Scale Design .......................................................................................................................... 6 3.2.1 3.2.1.1 Material Selection for Full-Scale ...................................................................................... 7 3.2.1.2 Full-Scale Pontoon Arm Design ....................................................................................... 7 3.2.2 Ballast Design ....................................................................................................................... 7 3.2.2.1 Sizing the Full-Scale Ballast Tanks .................................................................................. 8 3.2.2.2 Material Selection for Full-Scale Ballast Tanks ................................................................ 8 3.2.3 3.3 Frame .................................................................................................................................... 6 Stability & Control System ................................................................................................... 8 Prototype Design ......................................................................................................................... 10 3.3.1 Frame .................................................................................................................................. 10 3.3.1.1 Sizing the Prototype ........................................................................................................ 10 3.3.1.2 Material Selection for Prototype ..................................................................................... 10 3.3.1.3 Prototype Pontoon Arm Design ...................................................................................... 10 3.3.2 Ballast Design ..................................................................................................................... 11 3.3.2.1 Sizing the Prototype Ballast Tanks ................................................................................. 11 3.3.2.2 Material Selection for Prototype Ballast Tanks .............................................................. 11 3.3.2.3 Airflow System ............................................................................................................... 11 3.3.2.4 Fabrication & Installation ............................................................................................... 12 3.3.3 Stability & Control System ................................................................................................. 13 3.3.3.1 Stability of the Prototype ................................................................................................ 13 3.3.3.2 Equipment and Software Selection ................................................................................. 14 3.3.3.2.1 Software .................................................................................................................... 15 3.3.3.2.2 Microcontroller ......................................................................................................... 15 3.3.3.2.3 IMU Digital Combo Board ....................................................................................... 15 3.3.3.2.4 Power Supply ............................................................................................................ 16 3.3.3.2.5 Relay ......................................................................................................................... 16 3.3.3.3 Programming ................................................................................................................... 16 3.3.3.3.1 Autonomous Control ................................................................................................. 17 3.3.3.4 Installation ....................................................................................................................... 18 3.3.3.4.1 Autonomous Control Wiring..................................................................................... 18 3.3.3.4.2 Switchboard Wiring .................................................................................................. 19 3.3.3.4.3 Switchboard Control Box .......................................................................................... 20 3.3.3.4.4 Solenoid Valve Mount .............................................................................................. 20 3.3.3.4.5 Dry Box ..................................................................................................................... 20 3.3.3.5 4 IMU Calibration .............................................................................................................. 21 Final Design Testing & Evaluation ....................................................................................... 21 4.1 Stability Testing .......................................................................................................................... 21 4.1.1 Introduction & Objectives ................................................................................................... 21 4.1.2 Experimental Setup ............................................................................................................. 22 4.1.3 Results ................................................................................................................................. 23 4.2 Submersion Testing .................................................................................................................... 23 4.2.1 Introduction & Objectives ................................................................................................... 23 4.2.2 Experimental Setup ............................................................................................................. 24 4.2.3 Results ................................................................................................................................. 25 4.3 Draft and Steady-State Keel Evaluation ..................................................................................... 25 4.3.1 Introduction & Objectives ................................................................................................... 25 4.3.2 Experimental Setup ............................................................................................................. 26 4.3.3 Results ................................................................................................................................. 26 4.4 Heave & Roll Displacement Testing .......................................................................................... 26 4.4.1 Introduction & Objectives ................................................................................................... 26 4.4.2 Experimental Setup ............................................................................................................. 27 4.4.3 Results ................................................................................................................................. 27 5 Conclusions ........................................................................................................................... 28 6 Recommendations for Future Designs .................................................................................. 29 6.1 Improvements in Design ............................................................................................................. 29 6.1.1 Pneumatic Arms .................................................................................................................. 29 6.1.2 Ballast Tanks ....................................................................................................................... 30 6.1.3 Dry Box ............................................................................................................................... 30 6.2 Design Innovations ..................................................................................................................... 30 6.2.1 Thrusters ............................................................................................................................. 30 6.2.2 Liquid Level Sensors .......................................................................................................... 30 6.2.3 On-Board Optics ................................................................................................................. 31 7 List of References .................................................................................................................. 31 8 Appendices ............................................................................................................................ 31 Table of Figures: Figure 1: Overall Design Arrangement ......................................................................................................... 3
Figure 2: Air supply system arrangement ..................................................................................................... 4
Figure 3: The controls dry box and breadboard-relay wiring setup .............................................................. 5
Figure 4: The full-scale model of the device generated using SolidWorks .................................................. 6
Figure 5: Transverse righting arm & hydrostatic property curves of the full-scale design........................... 9
Figure 6: Diagram of the airline system...................................................................................................... 12
Figure 7: Left to right from top; solenoid valves, 4-way manifold, T-valve, air pressure regulator,
compressed air tank, and hose bundle ......................................................................................................... 13
Figure 8: Transverse righting arm and hydrostatic property curves formulated using GHS ...................... 14
Figure 9: The Arduino Mega microcontroller and 6-DOF IMU combo board ........................................... 15
Figure 10: The Elenco 20VDC power supply and Kyotto DC solid state relay ......................................... 16
Figure 11: The LabVIEW virtual instrument created for autonomous stability control ............................. 17
Figure 12: A schematic of the autonomous control system wiring ............................................................. 18
Figure 13: A schematic of the manual switchboard control wiring ............................................................ 19
Figure 14: Fiberglass manual switchboard control box .............................................................................. 20
Figure 15: Calibration curves for the inertial measurement unit ................................................................ 21
Figure 16: Schematic of the wave tank experimental apparatus ................................................................. 22
Figure 17: The device during testing in the Wallace Pool, and the experimental setup ............................. 24
Figure 18: An illustration of the draft (T) of a floating vessel .................................................................... 26
Figure 19: Impulse application points for heave and roll displacement ..................................................... 27
P a g e | 1 1 Introduction
1.1 Purpose
The Ryan Beaumont Corporation, in conjunction with a team of mechanical engineering
students from the University of Maine, is working to develop a submersible geotechnical
investigation device called Triton.
Currently, surfaced-based techniques are used in seabed investigations. A surface vessel
with a moon pool will typically use a long pipe as a borehole casting between the vessel and the
seabed. However, there are several drawbacks to this means of investigation:
 The amount of time required to mobilize equipment and perform the investigation, which
can take upwards of 3 months
 High associated cost
The goal of the senior capstone Triton project was to offer solutions to these and many other
problems encountered in surfaced-based investigations. Figure 1 summarizes some problems and
proposed solutions.
Table 1: Investigation issues and associated solutions that Triton hopes to offer [1]
Triton will be primarily used to assist in the development of offshore renewable energy sites
for Maine Hydrokinetic (MHK). The advantages of offshore wind and tidal energy sources are
many:
 Offshore energy is more predictable than other renewable sources
 These sources are emission-free
 Many MHK technologies are not visible or audible from shore
The total market for tidal and wave renewable energy is worth up to $746.6 billion in the
period of 2010-2050, with the market reaching $64.9 billion per annum in 2050 (Carbon Trust,
2011). For a number of remote communities located near MHK resources, the growth
opportunity is enormous.
P a g e | 2 1.2
Scope of Full-Scale Model Design
The student design team set out to come up with a preliminary design of a completely
submersible device that is limited to accommodating for drilling, cone penetrometer tests, and
sampling in underwater geotechnical investigations. The team then tested the viability of the
design by assembling a scaled prototype of the device and running various performance tests.
For the safety of all personnel involved, the submersible is designed to be used in calm
ocean conditions, and therefore was designed to a one year storm as a conservative limit. Except
for the forces and moments produced by the geotechnical equipment, no other specifications for
the geotechnical devices were included in the scope of this project. The Ryan Beaumont Co. has
taken responsibility for the design of the suction caisson anchoring system, so the student design
team engineered the full-scale submersible around the company’s plans in that regard.
Given the above design assumptions and constraints, the original design parameters for the
full-scale Triton device that needed to be met by the student design team include:
 Be towable by a one-ton hydraulic winch behind a chartered vessel
 Counteract forces and moments caused by the geotechnical equipment
 Comply with trailer size restrictions of 48 feet in length and 8.5 feet in width
 Have the ballast system control the ascent and descent of the vessel
 Control with umbilical lines running from the chartered vessel to the Triton
1.3
Scope of Prototype Design
The prototype fabricated in the spring semester is a scaled-down and simplified model of
the full-scale design. The scale was chosen to be one tenth of the original size to allow the
prototype of the device to fit transversely in Crosby Laboratory’s wave tank. Simplifications to
the prototype took place in various aesthetic alterations and material changes. For example, the
truss frame has a reduced number of members to make the construction of the device easier and
to minimize redundancy in strength. Also, the material of the ballast tanks has been changed
from steel to aluminum to achieve similar weight to buoyancy ratios for the prototype and fullscale model.
Components of the prototype were configured and sized by the design team, although
much of the equipment necessitated by the design, such as air pumps for ballast tanks, are to be
purchased. All fabrication of the prototype took place in the Crosby Laboratory under the
supervision of graduate students and professors. The prototype was subjected to stability testing
in the wave tank in Crosby Laboratory and to submersion testing in the Wallace Pool at the
Memorial Gym. A comprehensive laboratory report was composed for the stability testing
process. This report discusses the final full-scale design, the final scaled prototype, the
development process for both, and an assessment of how well the scaled prototype worked.
P a g e | 3 The
T main dessign parametters for the scale-model pprototype off the Triton ddevice are ass
follows:







2
Follow a one--tenth scale factor for the basic dimeensions of thhe prototype
Maintain
M
the same weight-to-buoyanccy ratio as thhe full-scale model
Construct
C
thee frame such that the posssibility of a structural faailure due to moments orr
fo
orces is remo
ote
Test
T the stabiility and subm
mersion abillity of the prrototype throough experim
mentation
Use
U scaled vaalues of the environment
e
tal factors annd parameterrs that influeenced the deesign
of the full-scaale model for testing pro
ocedures
Develop
D
a ballast control system to au
utonomouslyy manage thhe stability off the prototyype
based on angu
ular displaceement readin
ngs
Create
C
a switcchboard to manually
m
con
ntrol airflow
w in and out oof the ballastt tanks as ann
allternative baallast controll
Overall Design Description
n
The
T finished design of thee Triton prottotype
consists of
o a truss-sty
yle frame maade of steel tubing,
t
two
aluminum
m ballast tan
nks that servee as pontoon
n stabilizers
while on the water su
urface, a mecchanical arm
m
mechanissm that lifts the ballast taanks up and out of the
way wheen the devicee is not in usee, and a conttrol system
that regulates the verrtical movem
ment and stab
bility of the
device. Figure
F
1 show
ws the overaall arrangemeent.
2.1
Fram
me
Umbilical
Fra
ame
The
T stainless steel tubing was ordered
d from
Online Metals
M
and th
he members were
w cut to length
l
primarily
y using a cho
op saw. For smaller
s
mem
mbers a bandd
saw was utilized. Latter all edges of the tubess were
o make the edges
e
smooth
h and easy to
o weld.
ground to
The
T memberss were joined
d together ussing a MIG
welder. The
T lower su
ubassembly of
o the frame was
fabricated first, the id
dentical uppeer subassem
mbly was
w then joiined
made seccond. These two pieces were
together by the uprig
ght connectin
ng pieces. Finally the
upper sup
pport structu
ure for the arrm mechanissm was
welded on.
o
Controls
Box
Dry B
P
Pontoons
Figure 1: Overall Dessign Arrangeement
P a g e | 4 2.2
Ballast Tanks
The ballast tanks were cut from aluminum tubing to specified lengths using a horizontal
band saw. Circles, the diameter of the tubing, were cut from a flat aluminum sheet to serve as
end caps, and were TIG welded on. Next, air inlet and water inlet holes were drilled in the tops
and bottoms of the tanks, respectively, using a drill press.
2.3
Air System
At the surface, the ballasting and de-ballasting of the device is controlled by compressed
air. The air is supplied by a tank filled to approximately 100psi. A line regulator is then
connected to prevent exceeding the working pressure of the hoses, valves, and fittings. The
regulator also allows for control of the pressure of the air in ballasting. After the regulator there
is a T-valve that permits either venting to the atmosphere or using the compressed air in the tank.
After the T-valve comes a 4 way manifold with breaks the air supply into the 4 necessary lines
for each ballast compartment. Each supply line has its own solenoid which controls air flow to
each of the compartments in the ballast tanks. The lines then travel down the umbilical, each to
its specific compartment. Figure 2 shows these components.
Figure 2: Air supply system arrangement
2.4
Control System
The control system was developed to monitor the ballasting and de-ballasting of the
device. Using an Arduino microcontroller, a six degree-of-freedom inertial measurement unit
(IMU) board, LabVIEW software, power supplies, relays, and a breadboard, the system is
P a g e | 5 capable of autonomous operation. The system works by using case structures in LabVIEW that
activate or de-activate relays to open or close solenoid valves depending on the angular
displacement of the device. The microcontroller and IMU board are located in a dry box
mounted on the submersible device that has been custom fabricated so that wires may run to a
laptop computer on the surface. The IMU is responsible for providing the angular displacement
input necessary for the control system.
Figure 3: The controls dry box and breadboard-relay wiring setup
3
3.1
Design Concept Process
Overview
The Triton vessel was designed to meet requirements made by R.M. Beaumont
Corporation (RBC). In the project proposal, the main objectives of the Triton vessel were to
safely carry geotechnical equipment to the seafloor, to provide a stable platform for geotechnical
tests performed, and to have the vessel return to the surface. Specific towing weight and size
limits were also set. RBC requested that our vessel accommodate drilling, rock coring, and soil
sampling procedures. The current procedures for these tests are slow, expensive, and are surface
based. To speed up a typically month long procedure, the Triton was to be designed to perform
its mission in 24 hours. By designing the vessel to satisfy the design and time requirements, the
expenses would be greatly lower than the current surface based method.
Although the team would create a design package for a full-scale Triton platform,
building the full-scale device was outside the scope of the project. Instead, the team undertook to
build a scaled down working prototype as a proof of concept exercise. In the following sections,
we first describe the full scale design we had finished by the end of the fall 2013 semester, and
then we describe the scaled prototype we designed and constructed during the spring 2014
semester to perform certain proof of concept tests.
P a g e | 6 3.2
Fu
ull-Scale Dessign
3.2.1 Frame
F
The
T target perrformance fo
or the full-sccale frame w
was to be ablee to withstannd the torquee and
the upwaard force of the
t rock coriing drill and the cone pennetrometer, respectivelyy. It also had to
be able to
o support thee weight of the
t payload, as well as thhe weight off one person should the
vessel neeed to be boaarded. Finallly, the vessell was designned to fit a toowable traileer of specificc size.
When
W
design
ning the full--scale framee, we follow
wed the workking stress ddesign proceedure
explained
d to us by Dr.
D Basu in his global strength
s
lectture, since iit is the metthod that is most
widely used in the US.
U Accordin
ngly, using SolidWorks
S
w
we constructted a full moodel of the fframe
and ran stress,
s
strain,, and displaccement analy
ysis of the frrame due to tthe forces appplied.
For the full-sscale design
n, we chose a Warren T
Truss, since it is a stroong truss annd the
memberss will only be
b subjected to tension and
a compresssion, no mooments. Thee full-size w
warren
truss fram
me is 2.25 meters
m
wide,, 7 meters lo
ong and 2.255 meters talll. Since the vessel mustt fit a
trailer, th
he width wass restricted to
t 2.5 meterss. The heighht and lengthh of the fram
me was depenndent
on the sizze of the pay
yload, which
h was given to
t us by RBC
C.
Figure 4: The full-sccale model of the device generated uusing SolidW
Works
Since the wid
dth of the vessel
v
was reestricted by road regulaations, we ddecided to ddesign
foldable arms to allo
ow the ponto
oons to raisee and lower. The geomettry of the arrms was desiigned
so that th
he arms wou
uld retract intto the frame when the veessel is on laand. When in water, the arms
deploy lo
owering thee pontoons below
b
the frrame and tuurning the ddevice into a catamaran type
vessel.
P a g e | 7 As for accommodating the exploration equipment, the cone penetrometer and the rock
coring drill were placed in the middle of the front and back sections of the frame in order to keep
the reactions symmetrical.
3.2.1.1 Material Selection for Full-Scale
The building material we chose to use for the frame is Type 316 Stainless Steel, chosen
mainly because of its corrosion resistance. It is also relatively cheap compared to other stainless
steel alloys, and has superior ability to be welded.
3.2.1.2 Full-Scale Pontoon Arm Design
Since the width of the vessel was restricted by road regulations, we decided to design
foldable arms to allow the pontoons to be raised and lowered, narrowing the footprint and
allowing the device to be transported more easily. The geometry of the arms was designed so that
the arms would retract into the frame when the vessel is on land. When in water, the arms deploy
lowering the pontoons below the frame and turning the device into a catamaran type vessel.
To achieve these design criteria, CAD software was employed to design the geometry of
the arm mechanism. Ultimately, a four-bar linkage with an added linear actuator was chosen. The
three links were 1.5m long, to be made with the same material as the frame. The actuator was
1.7m long fully retracted, with a stroke of 0.66m. The hinges were unique and would have to be
custom machined.
3.2.2
Ballast Design
The ballast tanks take on two major functions in relation to the mobility of the structure:
First, the tanks need to perform as pontoons to keep the vessel afloat while it is being
towed out to the geotechnical location of interest. To do this, the pontoons were designed to be
completely empty during towing to provide as much buoyant force as possible to elevate the
frame and equipment out of the water. This will minimize the overall drag created by the vessel
and will allow it to be towed much easier. The remaining factor creating drag in the water is the
pontoons themselves. To accommodate this, the pontoons were designed as hydrodynamic as
possible. The final design locates the ballast tanks in a catamaran configuration with one tank on
each side of the structure.
The second function of the ballast tanks is to control the buoyancy of the structure during
ascent and descent. The levels of water inside of the tank were designed to be monitored at all
times to maximize desired ascent and descent rates as well as controlling the stability of the
structure under water. Each ballast tank is to be divided into three compartments to create
bulkheads. The bulkhead water volumes would be controlled separately to increase stability and
counteract any undesired motions.
P a g e | 8 To initiate descent, the ballast tanks will be filled with a desired amount of water and air
will be pumped out of the tanks to regulate the pressure. This will create negative buoyancy and
allow the vessel to sink to the ocean floor. To ascend, air will be injected into the tanks as water
is simultaneously pumped out. The buoyancy will once again become positive and elevate the
vessel to the surface.
3.2.2.1 Sizing the Full-Scale Ballast Tanks
When designing the physical properties of the full-scale ballast tanks, the main focus is to
trap enough air to counteract the entire weight of the structure to keep afloat during the towing
procedure. This weight includes all payloads as well as all of the hull components and any
additional weight due to environmental conditions. Since the tanks will be required to hold
pressure, the most practical shape for the tanks is long cylinders with rounded edges. This
cylindrical shape was derived from common pressure vessel and pontoon practice. The buoyant
force created by the entrapped air was calculated to be greater than the weight entirety of the
vessel, this creates reserve buoyancy. Reserve buoyancy is important to accommodate any added
weight and also adds to the stability of the structure. This extra buoyant force also takes into
consideration damage criteria; if one tank becomes damaged and fills with water the vessel still
possesses enough buoyant force to reach the surface. Also considered during the ballast tank
design is the transportability. The tanks are connected to mechanical arms on the frame in order
to fold upward during transportation to conform to traffic regulations. Due to this, the maximum
tank diameter was limited and the ballast tanks were designed to be slightly longer than the
frame to reach appropriate buoyant force.
3.2.2.2 Material Selection for Full-Scale Ballast Tanks
The material chosen for the full-scale ballast tanks is ASTM-A36 Structural Steel. This is
common steel with relatively high yield and ultimate strengths. When calculating the stresses on
a pressure vessel the stresses act mainly in two directions, longitudinally and along the
circumference of the structure. Typically the hoop, or circumferential, stress is twice that of the
longitudinal stress. In this case both stresses are well under the yield strength of the material. The
remaining failure method for the tanks is buckling. This is counteracted by the bulkheads, which
act as stiffeners for this loading case. The steel thickness is then determined by the pressure at
the maximum operation depth of 70 meters. The tanks need to be thick enough to tolerate the
pressure as well as any small impacts during the expedition, yet too thick will have large impacts
on the overall weight.
3.2.3
Stability & Control System
During the fall semester, the control system design subgroup was primarily concerned
with stability analyses that would be necessary to understand and develop a working control
system in the spring semester. Concepts were learned from Professor Thiagarajan in MEE 489,
P a g e | 9 Offshore Floating Sy
ystems. Altho
ough it was primarily diirected towarrds platform
ms such as oill rigs
and offsh
hore wind turbines, this course
c
proviided some prractices and backgroundd theory in thhe
engineeriing of those devices thatt led us to the final desiggn of our undderwater devvice.
As
A a part of th
he class, num
merical stabiility analyses were condducted for traansverse andd
longitudiinal situation
ns above and
d below wateer for the fulll-scale devicce, as well aas towing
situationss. The analyses showed that the stab
bility of the ffull-scale devvice is of greeat concern only
in the traansverse direection. Thesee methods off computatioon were ultim
mately disreggarded in favvor
of a Geneeral Hydrosttatics Softwaare analysis during the sppring semester at the reccommendation of
Professorr Thiagarajaan. However,, we were ab
ble to take aw
way from thee calculationns that the
limiting factor
f
for thee stability off the device, full-scale orr prototype, is in the trannsverse direcction.
A stability an
nalysis of thee full-scale design
d
using GHS showss that the maaximum righhting
arm of th
he device occcurs at a tran
nsverse heel angle of 13..07 degrees, and from thhen on the arrm
decreased
d steadily do
own to an an
ngle of vanishing stabilitty of about 554.92 degrees. The analyysis
assumed that geotech
hnical payloaads were 4x4
4x6 foot boxxes, and therrefore the shhape of the cuurve
took an odd
o formatio
on. Because of
o this assum
mption in geoometry, it iss concluded tthat the desiggn is
only safee to remain at
a transverse inclinationss under 13 deegrees. The rrighting arm
m curve and a plot
of hydrosstatic properrties are show
wn below.
Figu
ure 5: Transv
verse rightin
ng arm & hyd
drostatic prooperty curvess of the full--scale designn
The
T most basic means of quantifying underwater stability is tthat the center of buoyanncy
must rem
main above th
he center of gravity. A ru
udimentary aanalysis of uunderwater sstability
concludeed that the ceenter of buoy
yancy of the full-scale deevice unfortuunately lies below that oof
gravity. Because
B
the prototype do
oes not neceessarily havee the same prroperties andd because it will
feature a stability con
ntrol system, this fact waas duly notedd but was noot discouragiing enough tto
u from mov
ving forward.
prevent us
P a g e | 10 3.3
3.3.1
Prototype Design
Frame
3.3.1.1 Sizing the Prototype
In the design of the prototype, we were concerned about the welded frame holding
together, as well as it being strong enough to support the payload, the arms, and the pontoons.
We chose to ignore the forces of the cone penetrometer and the drill, since we do not have
equipment able to simulate the forces to scale, and since the full-scale model was already
designed and analyzed with the forces taken into account.
Part of our capstone includes the testing of the device, so the prototype needed to be sized
to easily fit in the wave tank and in the university pool. We decided to design it to a one-tenth
scale in order to be able to fit the vessel transversely in the wave tank.
Another sizing criterion was the scaling of the weight. Since the weight is proportional to
length cubed, scaling down the size of the device by 1/10 meant scaling the weight by 1/1000.
This proved impossible with the prototype frame, whose members would not have had sufficient
strength if we had used correctly scaled wall thickness. So we accepted the inevitable extra
weight and compensated elsewhere.
3.3.1.2 Material Selection for Prototype
As mentioned in the Sizing section, choosing the material came down to scaling the
weight, as well as choosing a material strong enough that would also be easy to weld. We started
with PVC tubes, because of its availability, which would speed up the fabrication and
installation. However, we quickly realized this material would be too heavy for our scale.
Later, we decided to test hypodermic stainless steel tubes. After building a model on
SolidWorks, we knew the weight would scale properly. It was not until we welded a joint to test
its strength that we realized the wall thickness was not high enough for welding.
We finally decided to go with stainless steel tubes with an outside diameter of 0.25 inches
and an inside diameter of 0.12 inches. These tubes have a wall thickness high enough to support
the welded joints. We decided to use 304 stainless-steel since it is strong, commonly used, and it
has a higher corrosion resistance than other steels, which is required because the vessel will be
used underwater.
3.3.1.3 Prototype Pontoon Arm Design
As discussed in the full scale design section above, we wanted to allow the pontoon arms
to be raised and lowered. The mechanism was scaled down and redesigned slightly: threaded
P a g e | 11 rods were chosen for the three links, vinyl ball joints were chosen for the hinges, and small
pneumatic actuators were chosen to drive the mechanism.
3.3.2
Ballast Design
3.3.2.1 Sizing the Prototype Ballast Tanks
To size the scaled model ballast tanks, a third degree exponential scaling factor was used
to determine the required volume inside the tanks. This volume would provide the correct
amount of buoyant force considering all other scaled elements. For simplification reasons the
original design of three bulkheads is decreased to two, in order to minimize umbilical size and
ease the manufacturing process. Slight shape modifications were also made to increase accuracy
of the operating volume and also for more practical fabrication. The final prototype shape of the
pontoons is a cylinder with flat-disc caps on the ends.
3.3.2.2 Material Selection for Prototype Ballast Tanks
The original material selection for the scale model design was PVC piping. This would
make fabrication very simple due to availability and price. PVC is commonly used in saltwater
because of its resistance to corrosion. The main problem with using this material is that the
ballast tank ratio of structural weight to buoyant force was dismal. The final material choice is
thin-walled aluminum. This provided accurate weight and performance specifications. The
aluminum proved to be lightweight, to be durable, and to have a constructible design. The
required thickness was recalculated to accommodate for the appropriate scaled operation depth.
As a result of availability, the dimensions for the ballast tank were increased slightly in order to
be able to buy off-the-shelf aluminum tubing.
3.3.2.3 Airflow System
We needed a system to transport air to the tanks when the Triton is on the bottom of the
pool. A bundle of 4 reinforced plastic tubes, one line to each tank, transports the pressurized air
to the tanks when necessary. The airflow system is made up of a compressed air tank, an air
pressure regulator, a T-valve, a four way manifold, and four solenoid valves which lead to the
hose bundle. Air coming from the compressed tank travels through the four way manifold;
which splits the single airline into four individual lines. The pressure regulator is located
between the pressure tank and manifold to control the pressure in each of the four hoses. Each
solenoid is responsible for directing air into one ballast tank, and the solenoids are able to be
independently controlled. This enables autonomous control of the structure during ascent and
descent. The airflow system is driven by the software written control system to offset the
moments created by the force of the waves acting on the vessel. A schematic of the airlines
system is shown below.
P a g e | 12 Figure 6: Diagram of the airline system
3.3.2.4 Fabrication & Installation
The hoses have quick connect fittings on both ends in order to make transport and storage
convenient. The ballast tanks also have aluminum tubes welded to the air inlet locations so that
there was material to tap with NPT threads for the male quick connect fittings. The male QC
fittings provide the locations for the umbilical lines to attach. A list of equipment specifications
is shown below.
1. Tanks (dimensions present on drawings in appendix)
a. Cut aluminum tube for tank walls using a horizontal band saw
b. Cut circular tank end caps out of aluminum sheet with an aluminum band saw
c. Tig weld caps to tubing to form closed tanks
d. Drill air inlet and water inlet/exit holes in tanks using ¼” drill bit on drill press.
e. Cut and tap aluminum pipe to form air inlet fitting
2. Umbilical/Air Line System
a. Cut bulk length hose to appropriate length
b. Used barbed fittings and hose clamps to ease assembly and increase safety
c. Assemble necessary hose segments from tank to manifold and manifold to
solenoid valves
d. Use spiral bundling in conjunction with zip ties to form umbilical components
into one, easy-to-maneuver system
P a g e | 13 Airline Components
 Solenoid Valve (4): 3/8” 12VDC NPT Electric, normally closed
 4-Way Manifold: 3/4” in, 3/8” out
 T- Valve: 3/4” in/out
 Air Pressure Regulator: 0-145 psi, 3/4” in/out
 Air Tank: 0-200 psi, 13 gallon capacity
 Hose Bundle: 3/4"
Figure 7: Left to right from top; solenoid valves, 4-way manifold, T-valve, air pressure regulator,
compressed air tank, and hose bundle
3.3.3
Stability & Control System
3.3.3.1 Stability of the Prototype
The control system has been designed to ballast our vessel quickly and maintain its
stability so that the vessel can descend to the ocean floor during a slack tide. Slack tide is the
short time, usually about 15 minutes, in between the high and low tides where there is little to no
waves. Of course, since a scaled prototype is being built, the distance the device must descend
and the time in which it must do so are also scaled. The vessel will not have much time to reach
the ocean floor, a little over two minutes when scaled appropriately, but the stability of the vessel
will greatly benefit from fewer waves.
The control system was designed to stabilize the vessel if it is thrown off balance due to
wave forces acting on it. This is to be done by adjusting the levels of air and water within the
segmented ballast tanks by electrically actuating solenoid valves. A geometric stability analysis
of the vessel using General Hydrostatics Software (GHS) led us to focus on its transverse
P a g e | 14 stability as
a opposed to
t its longitu
udinal stabiliity. This is laargely due too the greaterr length of thhe
device in
n comparison
n to its width
h. Using GH
HS, we were aable to estim
mate the trannsverse heel aangle
that woulld cause the vessel to ov
verturn at thee water’s surrface to be appproximatelyy 40.65 degrrees.
The prog
gram also com
mputed a fav
vorable valu
ue of the mettacentric height of the deevice at 0.7661
meters. This
T is an atttribute of thee design becaause in geneeral, the highher the metaccentric heighht of
an objectt the more sttable it is on the water’s surface.
Figurre 8: Transv
verse righting
g arm and hy
ydrostatic prroperty curvees formulateed using GHS
S
The
T most basic criterion for
f underwatter stability is that the ceenter of buoyyancy of thee
vessel is higher than its center off gravity. Un
nfortunately, the geometrric design off the prototyppe is
such thatt the center of
o gravity wiill always rem
main slightlyy higher thann that of buooyancy. Thiss is
because the
t center off gravity liess above the to
op of the balllast tanks, w
which are thee main sourcce of
buoyancy
y. For the prrototype, the difference between
b
thesse values is ccalculated too be
approxim
mately 1.11 inches assum
ming the tank
ks are half-fiilled with waater. This reppresents a vaalue
of about 10% of the total
t
height of
o the devicee. We determ
mined that thhe capabilitiees of the conntrol
system arre able to account for thiis flaw. Outsside of this, an underwatter stability aanalysis is qquite
complex.. GHS is lim
mited to stabiility at the water’s
w
surfacce and thereffore experim
mental testingg was
required to gain a tru
ue sense of th
he performan
nce of the veessel underw
water especiaally with the
ussed in furtther detail inn the design ttesting sectioon of
assistance of the conttrol system. This is discu
the reporrt.
3.3.3.2 Equipmentt and Softwa
are Selection
Itt was decided that the co
ontrol system
m could be deesigned usinng LabVIEW
W software annd an
Arduino Mega micro
ocontroller board. A six-degree-of-frreedom IMU
U Board was implementeed to
ultimatelly gain a meaasure of the roll, pitch, and
a yaw anglles of the veessel. To extrract the dataa
from the IMU board we use the Arduino
A
Meg
ga, and to reecord the datta we use LaabVIEW. A
Virtual In
nstrument (V
VI) was writtten using LaabVIEW to aacquire a siggnal from thee IMU boardd
through the
t microcon
ntroller and then
t
convertt the readinggs to angularr displacements. To keepp our
vessel staable, our con
ntrol system is able to acctivate solenooid valves too control thee airflow intoo the
P a g e | 15 ballast tanks and create righting moments to offset the angles created by the waves. To activate
these solenoids requires additional equipment such as power supplies and relays.
3.3.3.2.1 Software
LabVIEW has been chosen to be the software to use for the control system. LabVIEW is
capable of collecting data and integrating the different segments of the control system. Using the
downloadable VI packages, we are given the LabVIEW functions that can easily take outputs
from the microcontroller and convert the signals into usable data. Details of the virtual
instruments created for this project are covered in depth later in the report.
3.3.3.2.2 Microcontroller
An Arduino Mega is used to drive the control system. The microcontroller is responsible
for taking signals sent from the sensor and transferring it into the LabVIEW software. The
microcontroller was chosen for its compatibility with most equipment and software. It is also
capable of running the solenoid valves by controlling the current that will open and close the
valves.
Figure 9: The Arduino Mega microcontroller and 6-DOF IMU combo board
3.3.3.2.3 IMU Digital Combo Board
The inertial measurement unit (IMU) combo board is made up of an ADXL345
accelerometer and an ITG3200 gyro. Implementing the IMU board with the microcontroller, the
roll, pitch, and yaw angles of the device can be determined. The calculated angles are used to
demonstrate the angles of the vessel during wave testing, and act to legitimize our stability
calculations experimentally.
P a g e | 16 3.3.3.2.4 Power Supply
The power supply is an Elenco Precision Quad Power X-581, which produces up to 20
volts DC, and is used to electrically actuate the solenoid valves. One power supply is capable of
powering two solenoid valves, and therefore two power supplies are required.
Figure 10: The Elenco 20VDC power supply and Kyotto DC solid state relay
3.3.3.2.5 Relay
The relays are manufactured by Kytech Electronics, and are 32 volt input and 4 amp, 60
volt output. One relay is required for each solenoid, and therefore four of them are necessary.
The relays act as the midway point between the stored power supply and each solenoid valve,
and control whether each valve is either open or closed. The relays are ultimately controlled by
the Arduino microcontroller board.
3.3.3.3 Programming
The original goal of the control & stability subgroup was to develop a system that was
capable of autonomous stabilization when the device experienced excessive angular
displacement. Using an IMU board, a microcontroller, solenoid valves, relays, and LabVIEW
software, such a system has been created. One concern that we had with this system is that it
might potentially create more stability issues than it solves if valves are rapidly activating and
deactivating in wave cycles. Therefore, a more rudimentary system was also built that allows a
user at the surface to actuate each valve manually in the event that our concerns were realized.
LabVIEW is a graphical programming platform that allows the user to essentially write a
computer programming code using virtual blocks that represent commands. It was ideal for our
application because it is nearly unparalleled data acquisition software, it is compatible with
Arduino microcontrollers, and it is software that we’ve all had brief experience with from
Mechanical Laboratory courses.
P a g e | 17 3.3.3.3.1 Autonomous Control
A VI was created that essentially takes the data readings given off by the IMU board
through the microcontroller, and then determines whether or not to signal the microcontroller to
activate a relay based off the readings. The decision is made depending on if the readings
represent a displacement greater than an arbitrary maximum heel angle in roll or pitch. Four
relays act as buffers between the power supply and the four solenoid valves. When activated,
they allow current to pass through them and on to the solenoid valves, which is how each valve
is opened. Once the microcontroller no longer activates the relay, current flow is discontinued
and the valve closes.
The first “Arduino Init” VI block is used to communicate with and control the
microcontroller by specifying the COM port, the Baud Rate, the Board Type, and the Connection
type. The “Init I2C” block allows the microcontroller to communicate to the IMU board and
collect its output data. The “I2C Write” blocks are allowing the microcontroller to control the
sensors on the IMU board, telling it when to start collecting data, and when to turn on and off.
The “I2C Read” block reads the information coming from the sensor, and the IMU board sends
out a voltage that can be converted into a corresponding angular displacement. The maximum
voltage output (256 mV) is sent from the IMU board when the sensor reads a 90 degree
displacement. Using this knowledge, we were able to divide the voltage by 256/90 (2.844) and
receive angular displacements ranging from 0 to 90.
Figure 11: The LabVIEW virtual instrument created for autonomous stability control
The data being collected is used as true-false criteria for case structure loops used to
activate the solid state relays. The case structure loop changes the VI based on the true-false
input. Inside the loop, the “Arduino Set Digital Pin” and “Arduino Write Digital Pin” reference
the location on the microcontroller where a signal will be sent to depending on the true false
P a g e | 18 status. If the loop is true, the microcontroller will send a “0” to the digital pin and the relay will
close the switch and open the solenoid valve. If the loop is false, the microcontroller will send a
“1” to the digital pin and the relay will open the switch and create a short in the circuit, closing
the solenoid.
3.3.3.4 Installation
3.3.3.4.1 Autonomous Control Wiring
The control system features a myriad of wiring connections that are necessary to both
record angular displacement data and activate solenoid valves. The wiring process requires the
purchase of many other equipment items such as 16 gauge copper wire, breadboards, and
terminal blocks. To ensure reliable wiring, wires must be firmly in position at each and every
connection. In some cases wire must be soldered directly to an object, and in other cases wires
must be connected to a breadboard using a terminal block which acts as a junction between the
two. The breadboard is a vital tool in the wiring scenario because it allows us to integrate a large
number of connections while also making the system more visually appealing. Pins on the
breadboard are interconnected in segments, so that a number of wires may meet within a segment
to connect them without the need for a soldered union.
Figure 12: A schematic of the autonomous control system wiring
P a g e | 19 First, the IMU is wired to the microcontroller board at the matching connection point
labels on each object. A USB attached to the microcontroller is responsible for transporting
information between it and the laptop computer. From the microcontroller, wires are strung out
to the breadboard where they meet with two input pins from each relay. Connecting to the two
output pins of each relay are a connection to the power supply and a connection to a solenoid
valve. The solenoid valves also feature another wire that is connected directly to the power
supply through the breadboard to complete the loop through which power travels. A diagram is
shown below that has been virtually developed for reference. Please note that the actual setup
features four solenoid valves and two power supplies, only two valves and one supply have been
shown in the figure for clarity.
3.3.3.4.2 Switchboard Wiring
The wiring for the alternative switchboard control system is nearly identical to that of the
autonomous control system. The only difference lies on the breadboard where the relays were
featured in the latter. Instead of relays, toggle switches are connected to the breadboard. Since
the relays were essentially acting as automated toggle switches in the case of the autonomous
control, it is clear that by placing actual switches at these locations we will be able to actuate the
solenoid valves manually. Refer to the wiring schematic for the switchboard scenario pictured
below. Please note that the actual setup features four switches and solenoid valves, only two of
each have been shown in the figure for clarity.
Figure 13: A schematic of the manual switchboard control wiring
P a g e | 20 3.3.3.4.3 Switchboard Control Box
A switchboard control box has been fabricated using fiberglass that features four control
switches on the top face and a hollow interior that houses the breadboard, and in the case of
autonomous control, relays. While running manual ballast control, each switch corresponds to a
solenoid valve which is actuated at the flip of a switch. The top face is attached to one side of the
box using hinges so that the face may be opened and closed to facilitate wiring changes. The
purpose of the box was to not only create a manual interface for ballast control, but to also
isolate the abundance of wires and connections into a transparent, enclosed region.
Figure 14: Fiberglass manual switchboard control box
3.3.3.4.4 Solenoid Valve Mount
To keep the solenoid valves in an upright and stable position, a mounting surface was
built using a wooden 2x4. A long horizontal piece was butted between two vertical pieces with
screws to keep the mount from simply resting flat on a surface. Two long screws were threaded
through the base plate of each valve and into the horizontal piece of wood. Not only does the
wooden mount keep the valves steady, but also organizes a crucial section of the airflow system.
The mount is visible in Figure 7.
3.3.3.4.5 Dry Box
The first step in the installation process was to create a dry box for the IMU board so that
it may be on board the device to record angular displacements. In addition, the Arduino
microcontroller had to also fit into this same dry box because long I2C connections (i.e. the IMU
to the Arduino) can generate significant noise in data readings.
We went about this issue by purchasing a Pursuit 40 dry box from Otterbox, and drilling
a hole on the top surface so that wires may run to the computer interface and solenoid valves on
the surface. Once the necessary hole-size was determined and the wires were fed through, the
hole was enclosed using a marine sealant. We ran into leakage issues with the marine sealant
alone, and therefore the next step was to seal the box entirely using silicone adhesive. Although
this was unfavorable because it permanently restricted access to the box’s contents, it was
necessary to prevent water damage to the electronics. Aside from using a compound latch to seal,
P a g e | 21 the Otterbox features interior padding to prevent impact damage to the objects and a web
hammock that limits movement of the objects within it. The dry box is shown in Figure 3.
3.3.3.5 IMU Calibration
To obtain accurate angle readings, the IMU board needed to be calibrated. The IMU board
readings, without calibrating the signal, start off with a small error and slowly grow larger as the
angle gets larger. To find the calibration curve, the correct angles were compared to the IMU
angle reading for known angles ranging from 0 to 90 by increments of five. A protractor was
used to accurately read the angle the IMU board was supposed to be reading. Each angle was
held for ten seconds and averaged to accurately obtain the angle readings from the IMU. The
IMU readings were graphed against the known angles, and a best fit trend line was created.
Using the trend line equation from Excel, we used the equation to manipulate the signal in the
LabVIEW VI to get more accurate readings from the IMU board. The calibration curves are
shown in the figures below.
Figure 15: Calibration curves for the inertial measurement unit
4
Final Design Testing & Evaluation
The Triton design team has conducted a number of experiments to validate the degree to
which the finished prototype meets the design objectives determined at the outset of the project.
An overview of each experiment, consisting of objectives, experimental setup, and results, is
included in the proceeding subheadings below. One of these experiments, stability testing in the
wave tank, was highlighted in a comprehensive laboratory report as a requirement for MEE 443.
This report may be observed in full in the Appendix.
4.1
4.1.1
Stability Testing
Introduction & Objectives
Stability testing was used as the experiment to satisfy the requirements of MEE 443, and
because of this was the most rigidly structured experiment conducted by the design team. The
wave tank in Crosby Laboratory was used to generate waves for this experiment. The primary
purpose was to observe the response of the device when subjected to scaled levels of extreme
P a g e | 22 environmental factors set for the full-scale design from the first semester. The objectives of the
stability testing are as follows:






4.1.2
Use the Crosby Laboratory wave tank to simulate environmental forces on the
submersible device
Introduce at least 5 different levels of wave magnitude to the device in two different
situations; when the device is floating and when it is fully submerged at the bottom of the
tank
Obtain data for the angular displacement (heel angle) of the device as a function of time
using a 6 degree of freedom accelerometer/gyro IMU Combo Board
Compare heel angle results to plots of wave amplitude generated by the wave tank
Determine the highest magnitude of wave strength that the device may withstand for each
situation (amplitude and test position) based on a maximum heel angle requirement
Plot wave amplitude and angular displacement vs. time for all 5 amplitudes and each test
position
Experimental Setup
To conduct the stability test, the most important pieces of equipment are the wave tank
and the IMU board. The wave tank is responsible for simulating the conditions at which stability
is desired, and the IMU board is the means by which transient angular displacement data is
measured. The IMU is integrated with the Arduino microcontroller board and LabVIEW
software so that these measurements may be logged and recorded. For underwater wave testing,
the ballast air-line system becomes necessary to flood the tanks and allow the device to
submerge. See the figure below for a schematic of the experimental setup, and Figure 6 for a
blow up of the air-line manifold. For complete equipment specifications refer to the Lab Report
in the Appendix.
Figure 16: Schematic of the wave tank experimental apparatus
P a g e | 23 Equipment / Instrumentation List:
1. Wave Tank
2. Triton Submersible Device
3. IMU Digital Combo Board
4. Microcontroller Board
5. Laptop Computer (2 required)
6. Air Tank
7. Air Pressure Regulator
8. Pneumatic Manifold
9. USB cable (30 feet) / 16 Gauge Wire (200 feet)
10. Rope Tether
11. Relay (4 required) / Breadboard
12. Power Supply (2 required)
4.1.3
Results
The stability of the device during wave testing was impressive in the transverse direction.
Longitudinal stability was also tested to confirm our hypothesis that the transverse direction was
the limiting factor, but no data was taken. Several different combinations of wave periods and
amplitudes were subjected to the device, often times failing to disorient the device more than 1015 degrees.
Unfortunately, all angular displacement measurements obtained come from an
inclinometer attached to the frame of the device. The IMU board that was intended to collect
transient angular displacement data failed to collect any meaningful information. The waves
within the tank created vibrations that ended up inducing erratic data that did not adequately
describe the behavior of the device. Although this was catastrophic to the development of useful
graphs and models, with the use of the inclinometer we were able to at least quantify an
approximation of the maximum displacements that the device experienced in each situation.
Refer to the lab report included in the appendix of this document for more specific results and
thorough summarization.
4.2
4.2.1
Submersion Testing
Introduction & Objectives
Submersion testing was the other integral experimental procedure that was conducted by
the design team. For this experiment the Wallace Pool in the Memorial Gym was used. The fullscale design required that the device make its 70 meter descent and ascent in less than 15
minutes each, allowing it to complete the travel safely within a slack tide. The depth of the pool
is 13 feet, which leads to a scaled descent time of just over two and a half minutes. Remaining
stable while submerging to the bottom of the ocean and while returning to the surface is crucial
P a g e | 24 to the performance of the full-scale design; this is due to the geotechnical equipment that is to be
on board the device that must be protected. To ensure stability, the autonomous control system is
utilized. The goals of the submersion testing are as follows:



4.2.2
Use the Wallace Pool to simulate ocean descent and ascent for the prototype
Complete the 13 foot ascent and descent of the device within the scaled slack tide
timeframe of 160.5 seconds
Remain stable utilizing both the autonomous ballast control system and manual control
Experimental Setup
The setup for submersion testing in the Wallace Pool is nearly identical to that of stability
testing in the Crosby Laboratory wave tank. One difference between the two is the test medium,
where the pool is now being used as opposed to the wave tank. Other differences are that only
one laptop computer is required since there is no longer a wave generation interface, and that no
tether is used because the device is held in position using a makeshift pulley system. The pulley
system consists of a long aluminum rod that rests on top of two diving boards located on the
edge of the pool, and a cardboard spool covered with duct tape that is threaded through the rod.
The umbilical is fed over the spool, and effectively limits the tension forces acting on the device
to act in the vertical direction. This is an effort to reduce the possibility of having two of the four
ballast tanks ballast or de-ballast quicker than the rest due to an inclination of the device from
tension acting horizontally in the umbilical. The results are smoother descent and ascent trials.
Refer to the equipment list in the previous section for the numbers in the pool experiment
schematic.
Figure 17: The device during testing in the Wallace Pool, and the experimental setup
P a g e | 25 4.2.3
Results
For the manual ballast control system, submersion testing was a large success. The
inherent instability of the device while underwater attempted to de-stabilize the device, but by
manually filling and adjusting each bulkhead with water with the use of switches it was possible
to reach the bottom of the pool and return to the surface without flipping. At least five separate
tests were run in which the device maintained stability, with descent times ranging from 26.8 to
116 seconds and ascent times ranging from 33.5 to 78 seconds. The large variation in times is
due to the nature of the system being manually controlled. As the user become more comfortable
controlling the device it was possible to speed up the process.
For the autonomous ballast control system, submersion testing began very promising but
ultimately ended up being a disappointment. The very first test that was run using the LabVIEW
designed system, the device made it to the bottom of the pool successfully in approximately 35
seconds. Shortly afterward, the dry box that was custom fabricated to house the IMU board and
Arduino microcontroller began to leak and allowed water into the box. The result was a damaged
IMU board that unfortunately made it impossible to continue assessing the potential of the
autonomous ballast control system. From that point forward, the manual switchboard system was
used to continue with testing.
4.3
Draft and Steady-State Keel Evaluation
4.3.1
Introduction & Objectives
The most basic form of testing conducted by the design team was the evaluation of the
submersible device’s draft and steady state keel. Draft is defined as the vertical distance from the
keel of an object (the bottom most point) and the waterline when an object is resting on the
water’s surface. A theoretical value of the draft has been calculated based on the weight and
geometry of the device. Steady-state keel is the inclination with which an object rests when
floating on the water’s surface. These parameters are crucial to the performance of any offshore
object because they have implications in the object’s stability. The objectives of these two brief
experiments are as follows:



Obtain the experimental draft by marking the waterline on the ballast tanks and
measuring the distance with a ruler
Compare the theoretical and experimental values of the draft, then alter any calculation
using draft accordingly
Determine an approximate steady-state keel of the device by observing the angular
displacement outputs from the IMU board while resting on a calm water surface
P a g e | 26 4.3.2 Experimenta
E
al Setup
Due
D to the sim
mplicity of th
hese two parrticular expeeriments, it iis possible too conduct theem
by simply
y placing thee device in th
he wave tank
k or the poool. The designn team chose to executee the
tests prio
or to subjectiing the devicce to stability
y testing wh ere a suspennded wave taank providess for
an easierr measurement of draft. Of
O course, no
ot all equipm
ment in the sschematic is necessary foor
data colleection becau
use the devicce is not subm
merged and waves are ggenerated. Thhe most critical
aspects of
o the experim
mental setup
p are the dev
vice itself, thhe microconttroller and A
Arduino in the dry
box, the laptop
l
comp
puter to colleect transient angular dispplacement, aand a closed--off airline soo
that the device
d
remaiins atop the water’s
w
surfaace. Figure 118 illustratess draft.
Fig
gure 18: An illustration of the draft ((T) of a floaating vessel
4.3.3 Results
R
An
A experimen
ntal measureement of the draft of the device yieldded a value oof 2.5 inchess,
which is approximateely 5/8 the outer
o
diameteer of the ponntoons. We hhad calculateed a theoreticcal
value of the
t draft to be
b approxim
mately 2.23 in
nches, resultting in a perccent error off about 12
percent. We
W hypothesize that thiss discrepancy
y lies in the values of steeady state keeel that weree
measured
d using the IMU, becausse not resting
g flat on the surface mayy cause different
measurem
ments of draaft at differen
nt locations on
o the devic e. Setting thhe device dow
wn in a calm
m
wave tan
nk resulted in
n a steady-staate keel of approximatel
a
ly 0.864 deggrees in roll aand 0.453
degrees in
i pitch. Thiss could be a result of thee imperfect nnature of thee geometry oof the due to the
fact that the
t prototyp
pe was fabriccated by hand
d, not autom
mated.
4.4
4.4.1
Heeave & Roll Displacemeent Testing
In
ntroduction
n & Objectiv
ves
Heave
H
and roll displacem
ment tests con
nsist of provviding an imppulse to the ddevice whilee on
the waterr’s surface an
nd with only
y air in the taanks to deterrmine if and how the devvice restoress
itself. A heave
h
displaacement test applies an im
mpulse vertiically downw
ward on the center of thee
device, and
a a roll displacement teest applies an
n impulse onn the most trransverse exxtremity of thhe
device (in
n this case, where
w
the tw
wo ballast tan
nks are conjooined on eithher side). Thhe responses of
the devicce from thesee circumstan
nces are impo
ortant to the design team
m because thhey have
ramificattions on the stability of the
t device in
n environmenntal conditioons. The objeectives of heeave
and roll displacemen
d
nt testing are as follows:
P a g e | 27 

4.4.2
Quantify the response when a heave impulse is applied to the top of the submersible
device
Quantify the response when a roll impulse is applied to the center of the ballast tanks
Experimental Setup
Much like the draft and steady-state keel testing, heave and roll displacement testing is
basic and may be done by placing the device in either the wave tank or the pool. Also like the
other tests, this may be conducted with the experimental setups of either stability or submersion
testing but does not need all of the capabilities of those setups. The design team chose to execute
heave and roll displacement tests in the wave tank. Refer to Figure 19 for a representation of
where the impulses might be applied for testing.
Figure 19: Impulse application points for heave and roll displacement
4.4.3
Results
Heave and roll displacement tests turned out to be quite successful. To quantify heave
displacement, we forced the device to be fully underwater by applying force to the top center of
the frame with. Its response was a violent return to the water surface with most movement
occurring in the Z-orientation. In roll displacement, the device was forced at just short of the
angle of vanishing stability as determined by the GHS model (40.65 degrees). The device
responded by flipping back into an upright position while oscillating in roll briefly until settling
down back in equilibrium. Our intention was to record the response of the roll displacement
using the IMU board, but similar to our issues in wave testing the data contained a significant
amount of vibration and therefore the data was not usable.
P a g e | 28 5
Conclusions
The prototype model based on the original, full-scale design has given us insight on how
a submersible device such as Triton may operate in real world applications. The design team set
out to validate the performance of the prototype by setting various design and testing
requirements based on the desired capabilities of the full-scale design.
The primary goal of the prototype was to remain stable during all phases of deployment,
including underwater and above-water situations. The model proved very stable when subjected
to several different wave amplitudes and wave periods, responding quite well and not showing
signs of instability that would lead to capsizing. The design of the prototype resulted in an
inherently unstable object underwater due to the center of gravity being higher than the center of
buoyancy. In addition, uneven descent and ascent led to the sloshing of water in the ballast tanks.
Despite these issues, the device was effectively submerged and returned to the surface well
within the target time restrictions using manual ballast control. Although the device did not
remain flat during the entire test, adjustments were made quickly enough to prevent exceeding a
dangerous level of heel. We were also able to submerge the device on one trial run utilizing the
autonomous control system prior to sustaining water damage.
Another goal for the design of the prototype was to achieve a high level of structural
integrity, which was met by welding the small, segmented members of the frame together. The
fabrication process left us with a very rigid and strong frame prototype. Constructed using steel
tubing, the frame can withstand great force without deformation or failure.
The prototype featured a pontoon arm mechanism that allows the position of the tanks to
be adjusted. The full-scale design called for retractable arms so that the width of the device does
not exceed state of Maine road regulations for the width of an object being towed by trailer.
Designed with pneumatic actuators, the mechanism keeps the arms in a horizontal position when
pressurized and in a more vertical position when decompressed.
Yet another goal for the Triton prototype was to conceive a control system that is capable
of collecting angular displacement data and using it to actuate solenoid valves that control the
flow of water into the ballast tanks. The IMU board, the equipment that collects angular
displacement, was to serve a dual purpose in that it could collect data for a laboratory experiment
in which transient angular displacement would be compared to the behavior of waves generated
in the wave tank. Two main problems arose with this system: the accelerometer was ineffective
in wave tank testing due to vibrations induced by the waves, and the dry box on board the design
was not designed robustly enough to keep out water for extended periods of time under the water
pressure at the bottom of the pool. Although the accelerometer successfully collected data when
rotated by hand, the data from wave testing proved completely unreliable and oscillated every
few milliseconds. As mentioned earlier, the autonomous control system was also successful prior
to sustaining so much water that the IMU board was damaged beyond repair.
P a g e | 29 The design process for the Triton comprised a full-scale design and a prototype scale
model. Both the full-scale model and prototype design were thoroughly developed with the use
of drawings and calculations. However, a great deal of time was spent on the fabrication of the
prototype model. As with many engineering projects, unanticipated problems arose frequently
that required rapid solutions so that the fabrication process could continue on pace. Regrettably,
we feel that the overall deliverables associated with this project could have been improved
slightly if the fabrication stage had been undertaken earlier in the spring semester. Issues such as
inadequate data collection, insufficient waterproofing, and troubleshooting the arm design could
have been overcome if they did not occur with such little time to go in the year. We felt that the
corrections and alterations that we made in order to reach the final product were as optimal as
possible in rectifying the problems that we encountered, given the amount of time left to solve
them.
6
Recommendations for Future Designs
Over the course of the year, we have identified a number of elements that could use further
improvement in design to enhance the overall effectiveness of the original Triton prototype. In
addition, we have developed some potential design innovations that future project groups could
take into consideration for a new and improved prototype.
6.1
6.1.1
Improvements in Design
Pneumatic Arms
The main concern with our pneumatic arms was that the actuators were not capable of
supplying the required force to actually actuate the pontoons. At their max operating force of
22lbs. at 100psi the tanks would only raise an inch. Deploying the arms was not difficult, but
raising the required the assistance of an operator. Therefore, more robust actuators that are
capable of supplying a greater force at a much lower pressure are desired. The arm mechanism
itself lends to this issue as well, the nature of the frame as a result of welding created a difficult
situation. Because the frame was irregular making the arms equal and level was very difficult.
Nylon ball joints were used for all the connections. This accounted for the play and offset, but
also allowed for extra movement of the tanks, and potential moment generation that the actuators
could not counteract.
The arm mechanism’s only flaw was that it took up space on the frame where the payloads
would be placed, and the arms on the opposite tank had to be oriented so that there was no
collision between the two. This forced the mounting points on the ballast tanks to not be
symmetrical. Our recommendation would be to design a simpler system that potentially
functions simultaneously in order to optimize space and streamline operational controls. Some
thought was put towards horizontally actuating arms, but that is difficult geometry to work out
with the frame cross members present.
P a g e | 30 6.1.2
Ballast Tanks
While we were quite happy with the choice of material and the overall performance of the
ballast tanks, one thing that could be improved on is the amount of sloshing present in the current
design. While it was taken into consideration in our prototype, we ultimately decided to go with
only two bulkheads per ballast tank to simplify the fabrication process. We recruited the help of
Matt Cameron, a welder with years of experience, to perform the job of welding the tank caps
onto the aluminum tubes since it proved to be quite difficult.
The current design features bulkheads that are approximately 0.4 meters long a piece. A
more ideal design would feature either more bulkheads or an even smaller scale size to reduce
the overall size of the ballast tanks. Featuring more bulkheads, or reducing the overall length of
the ballast tanks, would reduce sloshing and greatly improve the stability of the device. To
understand how this would positively affect the design, consider a rectangular Tupperware
container and a water bottle. Imagine both are half-full of water, and then that they are shaken
back and forth. The water bottle experiences a much lesser degree of sloshing because there is
less area for the water to move in the container horizontally.
6.1.3
Dry Box
One of the most consistent sources of issues on our project was the integrity of the controls
dry box. On two separate preliminary descent tests, a considerable amount of water penetrated
the box and marine sealant. To protect the electronics we decided to seal the box entirely using a
silicone adhesive. Clearly this is a major drawback because the box may no longer be opened to
adjust the electronics inside. The next step in the design of a dry box is to develop it such that it
remains dry but also maintains accessibility to the contents of the box.
6.2
6.2.1
Design Innovations
Thrusters
The need for thrusters was expressed to us in a design review with RBC to potentially
avoid rotation of the Triton during decent. Rotation could cause unnecessary twist on the
umbilical and its connection points. During testing we found that if care was taken to ensure the
umbilical did not have any twist in it that the Triton would not rotate during decent and ascent in
idealized slack tide conditions, and only marginally in wave testing scenarios.
6.2.2
Liquid Level Sensors
One potential addition that could be made to the Triton project is by adding liquid level
sensors, or having other means of determining how much water is in the ballast tanks at any
given time. This could be beneficial to the design because it would then become possible to
determine precisely when the device reaches neutral buoyancy. Having this information would
P a g e | 31 allow the design team to stop allowing water into the tanks once there is already enough to begin
descent.
6.2.3
On-Board Optics
The need for on-board optics was apparent when we found out that the Wallace Pool has a
slanted bottom surface at the deep end of the pool. Being able to see which tanks are oriented on
the slope could allow for a more controlled ascent start by ballasting the lower tanks first in order
to reach equilibrium. Optics would also be useful in controlling the landing. As the floor
approaches, the operators could blast a small amount of air into the tanks to slow decent to a
smooth gradual landing.
7
List of References
[1] R. M. Beaumont, “Triton: For Seabed Geotechnical Investigation,” R. M. Beaumont Corp.,
Brunswick, ME, Prop. DE-FOA-0000715, July 3, 2012.
8
Appendices
I Triton Offshore Device: Formal Lab Report
Measuring stability of the device in mechanically induced waves
Crosby Laboratory
University of Maine
Orono, ME 04469
May 7, 2014
Report Composed By:
Thomas Allain
Paul Amsden
Ethan Gray
Brady Jacques
Erik Medina
Matthew Storgaard
Matthew Waldroup
II Table of Contents:
Introduction: .................................................................................................................................................. 1 Objectives: .................................................................................................................................................... 2 Apparatus, Equipment, & Instrumentation: .................................................................................................. 3 Equipment / Instrumentation List: ............................................................................................................ 4 Theory: .......................................................................................................................................................... 5 Procedure: ..................................................................................................................................................... 7 Overview of LabVIEW VI Development: ................................................................................................ 8 Results ........................................................................................................................................................... 8 Conclusions ................................................................................................................................................. 10 References ................................................................................................................................................... 11 Appendix ..................................................................................................................................................... 11 1 Introduction:
The goal of the Triton project is to construct a submersible vessel that supports geotechnical
devices intended to perform testing on the ocean floor. The vessel will be able to maintain
stability while being towed on the water's surface to various locations, and also while the device
is deployed to the ocean floor. The testing equipment on board the vessel that will perform the
geotechnical investigation will exert reactive forces that the vessel needs to be able to
handle. The current method of performing these geotechnical tests is very costly and can take up
to a week to perform. The goal of the Triton project is to perform the same tests at a much lower
cost and within 24 hours.
Aside from maintaining structural integrity, the most important result of the Triton project is that
the device remains stable and upright during all phases of deployment. Ensuring that the device
will not become severely disoriented at various current magnitudes is the most effective way of
illustrating this desired experimental outcome. In order to accomplish this, the design team will
utilize the capabilities of the wave tank located in the Crosby Laboratory. The aim is to subject
the vessel to a range of wave frequencies and heights, and to then plot the data obtained from an
accelerometer that will be located onboard. The accelerometer, while very useful in analyzing
the motion of an object, will be used in this instance as a means of obtaining the angles at which
the device becomes tilted when subjected to the waves.
In an ideal experiment, the design team would like to have an uncertainty in the results that is
less than 5 percent. This is because the stability of an object in a fluid is very sensitive, and
therefore conclusions as to whether the device will be stable at various wave amplitudes may not
safely be drawn unless there is a very high level of certainty in the results. In order for this goal
of uncertainty in results to be achieved, the uncertainty of the measured data will also need to be
very low.
The variables to be tested in the proposed experiment are heel angle, wave amplitude, wave
frequency, and time. Heel angle and wave amplitude will be plotted as dependent variables on
the ordinate axis, while time is treated as the independent variable on the abscissa. Placing heel
angle and wave amplitude on the same graph with multiple ordinates could be useful in creating
a visual demonstration of the device’s orientation at various points in the wave sequence. An
acceptable heel angle is formulated based on requirements for the device; this heel angle will act
as an upward limit for the magnitude of disorientation that the device may experience. The range
of wave amplitude will be determined based on environmental conditions on the three locations
of interest that the original design was engineered for. A significant wave height was found last
semester for the locations to be approximately 1.159 meters. However, a scale model is being
constructed and therefore the maximum wave amplitudes must also be scaled. Wave heights and
many other parameters do not scale linearly, so background computational work is necessary.
Time intervals for the experiment are in the range of 1-2 minutes. Time intervals of this
2 magnitude provide enough data to be thorough in assessing the stability while avoiding the
possibility of being redundant.
As touched upon previously, the basic nature of the experiment is to assess the stability of a scale
model of the Triton device using the wave tank in Crosby Laboratory. The wave tank has an
established LabVIEW interface that the design team will use to obtain transient wave amplitude
data. The wave tank is approximately 1 meter wide, 1 meter tall, and 6 meters long with a water
depth around 0.7 meters. A picture of the wave tank is shown in Figure 2 below.
Figure 1: Photo of the wave tank to be used for the experiment, located in Crosby Laboratory
In order to obtain the information necessary for this experiment, a number of pieces of
equipment and instruments are needed. The primary pieces of equipment necessary to collect
data are an IMU Digital Combo Board, a Microcontroller Board, and two Laptop Computers to
process data being collected by the IMU Board and by the wave tank interface.
The vessel will be placed in the tank and subjected to several magnitudes of wave heights while
floating to determine the most extreme wave condition for each circumstance that the device may
encounter and remain stable enough to not exceed a maximum heel angle. The design team
estimates that a minimum number of 5 different wave magnitudes will be sufficient in capturing
a spectrum of how well the device will perform in a wide range of conditions.
Objectives:


Use the Crosby Laboratory wave tank to simulate environmental forces on the
submersible device
Introduce at least 5 different levels of wave magnitude to the device when it is floating
3 



Obtain data for the heel angle of the device as a function of time using a 6 degree of
freedom accelerometer/gyro IMU Combo Board
Compare heel angle results to plots of wave amplitude generated by the wave tank
Determine the highest level of angular displacement of each trial and compare that to the
maximum allowable heel angle
Plot wave amplitude and heel angle vs. time for all 5 amplitudes and each test position
Apparatus, Equipment, & Instrumentation:
The experiment conducted by the design team necessitates several instruments and pieces of
equipment that are used to create, obtain, and record relevant data. First, the wave tank located in
Crosby Laboratory is instrumental because it is the means by which waves and currents are
propagated. The wave tank is complete with an interface that provides for the collection of wave
amplitude as a function of time, from which it is possible to calculate frequency and other wave
parameters of interest.
To collect heel angles as a function of time, an IMU Digital Combo Board that possesses an
accelerometer and gyro is mounted on the device. This combo board is capable of capturing
motion in all 6 degrees of freedom, and can be paired with an Arduino microcontroller board.
The microcontroller board is the means by which movement data is relayed to a laptop computer
for further processing and future reference.
Because the nature of the experiment requires the device to be in water, a number of
waterproofing elements are needed for the equipment exposed to the water. Refer to Figure 3
below for a visual representation of the experimental apparatus.
Figure 2: Schematic of the experimental apparatus
4 Figure 3: Diagram of the airline system
Equipment / Instrumentation List:
1. Wave Tank
 Tank Size: approximately 1 meter wide, 1 meter tall, and 6 meters long
 Water height: approximately 0.7 meters
 Interface: Compatible with a laptop computer to obtain wave data
2. Triton Submersible Device
 Pontoons
 Material: Aluminum T6-6061
 Size: 0.8 meter long, 0.1016 meter outside diameter
 Frame
 Material: 304 Stainless Steel
 Size: 1/4” O.D., 1/8” I.D., length varies by member
3. IMU Digital Combo Board
 Accelerometer Model: Analog Devices ADXL345
 Gyro Model: IvenSense ITG 3200
 Input: 3.3 volts
4. Microcontroller Board
 Model: Arduino Mega 2560 Microcontroller
 Input Voltage: 7 to 12 volts
 Input/Output: 54 digital I/O pins
5 5. Laptop Computer (2 required)
 Model: Lenovo ThinkPad W510 or Dell PP39L
 Required Software: LabVIEW and Arduino IDE
6. Air Tank
 Capacity: 13 gallons
 Pressure Range: 0-200 psi
7. Air Pressure Regulator
 3/4” Diameter in/out
 Pressure Range: 0-145 psi
8. Pneumatic Manifold
 3/4” Diameter Y-Valve
 4-Way Manifold
 3/4” diameter in, 3/8” out
 Solenoid Valve (4 required)
 Model: US Solid 3/8” NPT Electric, normally closed
 Part Number: JFSV00006
 Barb Fitting (5 required)
 3/4” Diameter Inlet Hose
 3/8” Diameter Outlet Hose (4 required)
9. USB cable (30 feet) / 16 Gauge Wire (200 feet)
10. Rope Tether
11. Relay (4 required) / Breadboard
 32V input, 4A 60V output
12. Power Supply (2 required)
 Model: Elenco Precision Quad Power X-581, 20VDC
Theory:
The methods by which this experiment collects data are such that there are very few
manipulations necessary in order to reduce data to results. As stated in the Introduction of this
report the parameters of interest are the heel angle of the device, the wave amplitude, wave
frequency, and time. The data that is to be collected directly are the wave amplitudes, wave
frequencies, and time. Since these parameters are obtained in their desired forms, no reduction is
required in these instances.
To convert the readings from the IMU into angular displacements a small conversion is
necessary. The program developed for the device reads an output from the IMU in least
significant bits (LSB), and converts it into an angular displacement. Each level of LSB
corresponds to a force in g’s that is being read in each of the three principal directions. The IMU
gives off a maximum of 256 LSB in each direction, which occurs at 90 degrees of rotation about
any axis and also when the force is highest. When the IMU exceeds a displacement of 90
6 degrees, a negative LSB
L is obtain
ned. Therefo
ore, the outpuut from the IIMU is multtiplied by a ffactor
6 to obtain th
he angular displacement
d
t and all dispplacements ggreater than 990 degrees
of 90/256
appear ass negative. A sample callculation of the
t angular ddisplacemennt conversionn is shown
below.
Although
h not directly
y related to data
d reductio
on, there is s ome computtational worrk and
programm
ming to be done.
d
The calculations arre required inn order to sccale the environmental
condition
ns that the wave
w
tank sho
ould introducce to the devvice and the computer prrogrammingg is
needed to
o predict thee magnitudess of waves th
hat the devicce may withsstand.
Modeling
g the scale model
m
of the submersiblee device withh GHS (Genneral Hydrosttatics) softw
ware
efficientlly calculates geometric properties
p
off the device ssuch as centeer of gravityy and center of
buoyancy
y as a functio
on of draft. In
I addition, the
t softwaree is also capaable of consttructing a
righting arm
a curve fo
or the devicee as a functio
on of heel anngle. The poiint at which the rightingg arm
curve cro
osses the x-aaxis represen
nts the ultimaate heel anglle the devicee may reach without beinng
able to reecover. For the
t prototypee, this angle is approxim
mately 40.65 degrees andd must neverr be
exceeded
d to remain stable
s
and up
pright on thee water’s surrface. The arrea under thee curve of thiis
plot signiifies the righ
hting momen
nt, or the am
mount of exteernal work reequired to orrient the devvice
at a given
n angle. Onee caveat to th
he advantagees of GHS sooftware is thhat the resultts may only bbe
valid for floating situ
uations, and therefore
t
an
n experimenttal approach is necessaryy to quantifyy the
performaance of the device
d
underw
water.
Figurre 4: Model geometry an
nd transversee righting arm
m curve for the prototyppe using GH
HS
7 As for the scaling of parameters, factors to take into account are average and significant wave
heights, and peak periods and frequencies. Appropriate scaling factors may be determined from
the table below, which was obtained from a proceeding technical report from an ASME
conference on Ocean, Offshore, and Arctic Engineering circa 2012.
Tables 1&2: Scaling factors derived for the testing of floating wind turbine models [1], scaled
values of environmental parameters
Parameter
Value
Avg. Wave Height (0.1) 0.073m
Sig. Wave Height (0.1)
0.116m
Peak Period (0.01)
1.07s
Peak Frequency (0.01) 0.0093Hz
Previously determined values for the environmental factors of interest are to be corrected
accordingly. The scale size factor designated for the Triton device is one tenth, and therefore a
value of 0.1 is to be used for the scaling variable shown in Table 1 above, lambda. A scaling
factor of 0.1 is translatable to a wave that can be produced by the wave tank. However for the
scaling computations of wave period and frequency, a larger scaling factor is in order. This is
because the one-tenth scale does not reduce the wave period and increase the wave frequency to
levels that may be accommodated by the wave tank. A scaling factor of 0.01 has been decided on
for this reason.
Procedure:
1. Multiple group members lift the fully assembled Triton device and place it in the wave
tank orientated with the port or starboard perpendicular to the wave direction
2. The device is then tethered via a rope to the upper wave tank frame. The USB chord for
the onboard measuring units is to be connected, along with the tether and ballast tank airlines
3. Once the on-board data recording equipment has been become operational, a brief test of
its response is done by simply pushing downward on any portion of the Triton
4. The LabVIEW VI outlined later in this section is launched to collect experimental data
8 5. The wave generator is then operated, executing the specified wave levels for the surface
tests. This is repeated at least 5 times, making sure to store each test labeled correctly via
the LabVIEW software
Overview of LabVIEW VI Development:
To get started, it was necessary to download the Arduino VI Package for Arduino adaptable
functions. Using the added Arduino functions, LabVIEW can be used to communicate with the
Arduino microcontroller. Refer to the Appendix for all specific block references.
The first “Arduino Init” VI block is used to communicate with and control the microcontroller by
specifying the COM port, the Baud Rate, the Board Type, and the Connection type. The “Init
I2C” block allows the microcontroller to communicate to the IMU board and collect its output
data. The “I2C Write” blocks are allowing the microcontroller to control the sensors on the IMU
board, telling it when to start collecting data, and when to turn on and off. The “I2C Read” block
reads the information coming from the sensor, and the IMU board sends out a voltage that can be
converted into a corresponding angular displacement. The maximum voltage output (256 mV) is
sent from the IMU board when the sensor reads a 90 degree displacement. Using this
knowledge, we were able to divide the voltage by 256/90 (2.844) and receive angular
displacements ranging from 0 to 90.
The data being collected is used as true-false criteria for case structure loops used to activate the
solid state relays. The case structure loop changes the VI based on the true-false input. Inside
the loop, the “Arduino Set Digital Pin” and “Arduino Write Digital Pin” reference the location
on the microcontroller where a signal will be sent to depending on the true false status. If the
loop is true, the microcontroller will send a “0” to the digital pin and the relay will close the
switch and open the solenoid valve. If the loop is false, the microcontroller will send a “1” to the
digital pin and the relay will open the switch and create a short in the circuit, closing the
solenoid.
Results
The data collected during experimentation by the IMU board failed to live up to the task set out
for it in collecting reliable transient angular displacement. During experimentation, it was
apparent that the waves introduced to the device were inducing detrimental vibrations that
caused the IMU to relay data that represented a rapid oscillation with periods on the order of
milliseconds. Several different trials of experiment were run, each producing results that were
misrepresentative of the actual behavior of the device.
This came as a surprise to the design team because the IMU had been tested on numerous
occasions by rotating and flipping the controls dry box and performed well. It is unclear whether
9 the equip
pment is simply limited when
w
operating in enviroonments exhhibiting a connsistent
frequency
y or whetherr the motion
n of the IMU
U was not lim
mited enoughh during testiing leading tto an
actual vib
bration of th
he object. To illustrate th
he ineffectiveeness of the experimentaal data colleccted
by the IM
MU board, a plot of the data
d is shown
n in Figure 55.
Figure
F
5: Daata collected by the inertiial measurem
ment unit
The only
y legitimate data
d collecteed in the expeeriment cam
me from the w
wave tank innterface. As
expected
d, the wave taank performed flawlessly
y and it wass possible to develop chaarts of wave
amplitud
de in Microso
oft Excel. Since there is no corresponnding transient angular ddisplacemennt to
compare to, only a saample chart of
o transient wave
w
amplittude was connstructed to avoid
unnecesssary redundaancy.
Figure
F
6: Traansient wavee amplitude data for a w
wave represennting peak frrequency
Many atttempts were made to seccure the IMU
U board withhin the box hhoping to cappture a state in
which su
uccessful data could be collected, butt ultimately nnothing cam
me of it. In ann attempt to
potentially address so
ome of the objectives
o
off the experim
ment, an incliinometer waas secured too the
center off the frame of the device and tests weere conducteed once againn and video was recordeed
during teesting. An ap
pproximate maximum
m
an
ngular displaacement for eeach trial coould be drawn
from it which
w
allows the design team
t
to comp
pare the expperienced levvels of displaacement to tthe
maximum
m allowable displacemen
nt calculated
d using GHS
S software.
Due to th
he restriction
ns of the wav
ve tank, it waas not possibble to subjecct the device to both a peeak
frequency
y and maxim
mum wave am
mplitude sim
multaneouslyy. Only certaain waves arre able to be
10 generated that are within a specific range of wave height to period ratio, and the ratio of peak
frequency and maximum amplitude fall outside this range. However, they were able to be
demonstrated separately. The approximate maximum angular displacements caused by 5
different waves are shown in Table 2 below.
Table 2: Experimental wave parameters and approximate induced angular displacement
Wave Period (s) H/L Ratio Wave Amplitude (m) Approx. Heel Angle (°)
1.1
0.03
0.029491
3°
1.1
0.06
0.058982
10°
0.85
0.06
0.037949
5°
2
0.05
0.11292
2°
0.6
0.05
0.020456
15°
Conclusions
Although transient angular displacement data was not obtained in this experiment, it was still
successful in determining that the Triton device will remain upright when subjected to scaled
environmental conditions in the transverse direction. In fact, the trial which caused the largest
displacement was only able to disorient the device by about 15 degrees. The maximum allowable
angle that it can experience and still possess a righting arm occurs at about 40.65 degrees, so
there is plenty of flexibility when it comes to the stability of the device during extreme
circumstances.
One significant conclusion to draw from wave testing is the relationship between the wave
period and the width of the device. The waves that are most disruptive to the transverse stability
of the device are those with periods on the same order as the end-to-end distance of the ballast
tanks. This is evidenced by the last trial in Table 2, which with a wave period approximately the
same as the width of the device (0.63m), features the smallest wave amplitude of all the trials but
the highest level of displacement. This is important to note because in a full-scale design, it
would be critical to avoid conditions in which wavelengths are not the same length as the
distance perpendicular to the wave direction. It is also important to note that aside from this, the
results provide no evidence to infer any other definitive relationships between wave period size
and angular displacement.
Although there is little evidence to back it up, it is hypothesized that there is a positive
relationship between wave amplitude and maximum angular displacement when comparing
waves with identical periods. The first trial in Table 2 features an amplitude that is half that of
the second trial, but they share the same period. The end result is an increase is an increase in
heel that is approximately 7 degrees higher when the wave amplitude is increased.
11 References
[1] Goupee, Kimball, Martin, Viselli. “Methodology for Wind/Wave Basin Testing of Floating
Offshore Wind Turbines”. OMAE 2012-83627.
http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleID=1733156
Appendix
Appendix A
Qnty. Description
Unit Price
Total
FIRST ORDER
1 3/8" NPT Electric Solenoid Valve 12-VDC Air
1 Arduino Mega 2560 R3
PN: JFSV00006
$29.99
PN: DEV-11061
$58.95
$29.99 US Solid
$58.95 Sparkfun
1 IMU Digital Combo Board
PN: SEN-10121
$64.95
$64.95 Sparkfun
PN: 1064K711
PN: 6516K110
PN: 92735A110
PN: 90264A430
PN: 92735A120
PN: 54155K86
PN: 5463K608
PN: 5454K81
PN: 6498K857
PN: 4952K114
PN: 52375K13
PN: 52375K13
PN: 52375K16
PN: 7432K33
PN: 4591K11
$4.91
$7.91
$5.49
$0.66
$5.55
$11.83
$7.37
$4.55
$26.89
$3.74
$87.00
$43.50
$17.80
$27.36
$1.86
$98.20
$110.74
$10.98
$5.28
$11.10
$11.83
$7.37
$9.10
$107.56
$29.92
$87.00
$43.50
$17.80
$27.36
$3.72
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
8 hose coupling 3/8" NPTF male, 3/8" coupling size
house couplin, sleeve Lok socket, 3/8" Hose ID, 3/8"
8 coupling
brass barbed hose fitting 3/8" hose ID x 3/8" NPTF Male
1 Pipe, pack of 5
brass barbed hose fitting adapter for 3/4" hose ID x 3/4"
2 NPTF male pipe, pack of 2
1 stainless steel hex nut 3/8" pack of 25
1 pressure sealing washer 3/8" pack of 5
PN: 6534K72
$4.33
$34.64
McMaster-Carr
PN: 6536K62
$11.09
$88.72
McMaster-Carr
PN: 5346K19
$8.78
$8.78
McMaster-Carr
PN: 5346K28
PN: 94804A325
PN: 93781A038
$9.29
$5.75
$11.09
$18.58
$5.75
$11.09
McMaster-Carr
McMaster-Carr
McMaster-Carr
1 stainless steel type A flat washer 3/8" pack of 10
1 Air regulator 145 max pressure 3/4"
PN: 93852A104
PN: 8812K38
$3.31
$57.02
$3.31
$57.02
McMaster-Carr
McMaster-Carr
SECOND ORDER
20
14
2
8
2
1
1
2
4
8
1
1
1
1
2
Nylon ball joint rod end, female
Threaded connecting rod, male
Grooved clevis pin, 3/8" w/ ring
Coupling nuts
Grooved clevis pin, 5/8" w/ ring
Hose & Tube Clamp
nylon tee fitting (black)
Brass port plug
Pivot-mount air cylinder
Pivot bracket
3/8" ID High-Pressure PVC Tubing clear 100ft length
3/8" ID High-Pressure PVC Tubing clear 50ft length
3/4" ID High-Pressure PVC Tubing clear 10ft length
Spiral Bundling Wrap-Around Sleeving clear 50ft length
Pipe Thread Sealant Tape: commercial grade white
1 diverting 3 port brass ball valve 3/4"
SME-Code Horizontal Pressure Tank without Top Plate,
13
Gallon Capacity, 14" Diameter x 23" Long
1
1 RTV sealant
1 Brass 37° Flared Tube Fitting
1 Rigid-Bristle Threaded-Arbor Cup Brush, carbon steel
1 flexible-Bristle Shank-Mount cup brush 1-3/4"
1 4" grinding wheel for angle grinder, pack of 25
PN: 4093T24
$49.70
$49.70
McMaster-Carr
PN: 9888K19
PN: 7462A22
PN: 50675K173
PN: 4771A38
PN: 4887A1
PN: 44165A11
$257.11
$9.84
$2.99
$17.48
$13.29
$5.76
$257.11
$9.84
$2.99
$17.48
$13.29
$5.76
$42.00
$42.00
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
www.webbsonline.
com
$190.34
$190.34
Onlines Metals
$58.04
$58.04
Onlines Metals
$13.43
$13.43
$12.42
$12.42
PN: 2W-160-10-12V
PN: 71-05205
PN: 5LXF3
PN: 5ZLN3
PN: 12070
PN: 10213
PN: COM-10926
PN: 247174
$38.95
$9.95
$13.90
$18.74
$4.95
$0.86
$0.15
$21.95
$155.80
$9.95
$13.90
$18.74
$9.90
$17.20
$1.20
$21.95
Onlines Metals
Component Supply
Company
Electric Solenoid
Valves
PBS Boat Store
Grainger
Grainger
Sparkfun
Sparkfun
Sparkfun
Office Depot
PN: 6534K74
$4.09
$4.09
McMaster-Carr
PN: 6536K23
$12.10
$12.10
McMaster-Carr
PN: 6536K42
$13.67
$13.67
McMaster-Carr
4 Way Heavy
Duty
Manifold,
3/8"ID,
out4"
1 Matala
6ft Aluminum,
6061-T6
Bare
Drawn 3/4"
Tubein,
3.87"
1 OD, .065" Thickness
1 24 inches by 48 inches Aluminum Bare Sheet 6061 T6
36" length of Welded Stainless Steel Tube 0.25" X 0.065"
1 X 0.12"
30" length of Hypodermic Tubing, Gauge: 6G/Reg, Part
#:HTX-06R
1
4
1
1
1
2
20
8
1
3/8" 12VDC Electric Brass Solenoid Valve
3M Marine Adhesive Sealant 5200 Black 3 oz.
Automotive Primary Wire, 16 AWG, 100 ft Black
Automotive Primary Wire, 16 AWG, 100 ft Red
Solder-able Breadboard
N-Channel MOSFET
Schottky Diode
30 ft A to B USB Cable
THIRD ORDER
Hose Coupling, Plug, Zinc-Plated, 1/4" NPTF Female,
1 3/8 Coupling Size
Hose Coupling, Sleeve, Zinc-Plated, 3/8" NPTF Male,
1 1/2 Coupling Size
Hose Coupling, Sleeve, Zinc-Plated, 3/4" NPTF Male,
1 1/2 Coupling Size
1
4
1
1
3
1
Hose Coupling, Plug, Zinc-Plated, 3/4" Hose ID, 1/2
Coupling Size
Hose Coupling, Plug, Zinc-Plated, 1/4" NPTF Male, 3/8
Coupling Size
Pressure - Sealing Washer for Screws & Bolts, 9/16"
Screw Size, Pack of 5
Pressure - Sealing Washer for Screws & Bolts, 1/2"
Screw Size, Pack of 5
0.25" OD x 0.065" WALL x 0.12" ID t-316/316L TUBE
36" Length
Cut Fee
PN: 6534K64
$4.54
$4.54
McMaster-Carr
PN: 6534K71
$2.61
$10.44
McMaster-Carr
PN: 93783A034
$8.17
$8.17
McMaster-Carr
PN: 93783A033
$14.80
$14.80
McMaster-Carr
PN: 4229
$18.91
$18.00
$56.73
$18.00
Online-Metals
Online-Metals
$6.61
$6.61
McMaster-Carr
$6.85
$6.85
McMaster-Carr
$5.00
$5.00
McMaster-Carr
$8.05
$8.05
McMaster-Carr
$7.12
$14.24
McMaster-Carr
FOURTH ORDER
Worm-Drive Hose Clamp, 1/2" to 29/32" Diameter, Pack
1 of 10
PN: 5415K32
Worm-Drive Hose Clamp, 13/16" to 1-3/4" Diameter,
1 Pack of 10
PN: 5415K16
1 Tapered Round Rubber Plug, Size 7, Pack of 5
PN: 9545K19
Multipurpose Aluminum Tube, 5/8" OD, 0.495" ID, 1'
1 Length
PN: 9056K68
2 Primer, Aerosol, Filler, 12oz, Gray
PN: 7929T1
2 Aerosol Paint, Low Odor, 12oz, Gloss Safety Yellow
1 Aerosol Paint, Low Odor, 12oz, Flat Black
PN: 75035T41
PN: 75035T41
$5.32
$5.32
$10.64
$5.32
McMaster-Carr
McMaster-Carr
FIFTH ORDER
Relay Solid State 32V DC Input 4A 60V DC Output 44 Pin
2 IMU Digital Combo Board
PN: 175222
PN: SEN-10121
$9.95
$40.00
$39.80
$80.00
Jameco Electronics
Sparkfun
PN: 6300-20
PN: 6500-04
PN: 6101-00
PN: 6112-01
$19.95
$8.95
$26.00
$1.95
$19.95
$8.95
$26.00
$1.95
TP Tools
TP Tools
TP Tools
TP Tools
1
1
1
1
SIXTH ORDER (INFRASTRUCTURE)
Medium Steel Nozzle Combo
48" Cabinet Siphon Hose, Straight
Standard 12" x 24" Cabinet Lens
Front Hose Gronmet
1 Skat Blast Cabinet Door and Funnel Gasket
Weather-Resistant Vinyl Foam (3/8" thick, 3/4" width,
10'
length)
1
1 Flexible Magnet Strip (5 ft)
1 Abrasive Blasting Media - Aluminum Oxide Grit 10lbs
OtterBox
Epoxy
Threat Tap
PN: 6217-00
$7.95
$7.95
TP Tools
PN: 93675K17
PN: 5759K28
PN: 3398K34
$3.29
$2.65
$30.16
$3.29
$2.65
$30.16
McMaster Carr
McMaster Carr
McMaster Carr
$20.00
$10.00
$8.00
TOTAL:
$2,304.23
0.088
0.050
0.600
0.075
0.225
0.050
0.038
0.200
0.250
0.350
0.450
0.500
0.650
0.225
0.150
0.700
UNLESS OTHERWISE SPECIFIED:
DIMENSIONS ARE IN METERS
TOLERANCES: 0.001m
NAME
DRAWN
PA
DATE
2/5/2014
TITLE:
CHECKED
ENG APPR.
Triton Frame Drawing
MFG APPR.
INTERPRET GEOMETRIC
TOLERANCING PER:
PROPRIETARY AND CONFIDENTIAL
THE INFORMATION CONTAINED IN THIS
DRAWING IS THE SOLE PROPERTY OF
<INSERT COMPANY NAME HERE>. ANY
REPRODUCTION IN PART OR AS A WHOLE
WITHOUT THE WRITTEN PERMISSION OF
<INSERT COMPANY NAME HERE> IS
PROHIBITED.
5
MATERIAL:
0.204" OD 304 stainless steel tubing
USED ON
NEXT ASSY
APPLICATION
4
FINISH
DO NOT SCALE DRAWING
3
Q.A.
COMMENTS:
For drawing purposes, dimensions are
taken from edges ("sides") of tubing.
During assembly, these dimensions
should be taken from the CENTERLINE
of tubing.
2
SIZE DWG. NO.
A
framedrawing
REV
SHEET 1 OF 1
SCALE: 1:8 WEIGHT:
1
9.25"
Overall Extended Length
6.25"
Retracted Length
3"
Stroke Length
0.62" OD
0.50"
0.38"
9/16"
Bore Size
0.38"
0.31"
0.25"
0.19"
0.157" Pin Dia.
#10-32 Thread
#10-32 UNF Ports
7/16"-20 Mounting Thread
7/16"-20 Mounting Thread
PART
NUMBER
http://www.mcmaster.com
© 2011 McMaster-Carr Supply Company
Information in this drawing is provided for reference only.
6498K857
Stainless Steel Double Acting
Pivot-Mount Air Cylinder
1.35"
0.20"
0.75"
0.50"
0.13"
0.19"
0.33"
0.16"
0.77"
0.57"
0.06"
PART
NUMBER
http://www.mcmaster.com
© 2013 McMaster-Carr Supply Company
Information in this drawing is provided for reference only.
4952K114
Pivot Bracket with Pin for Switch-Ready
Stainless Steel Air Cylinder
6"
1 3/16"
3/16"
1 3/16"
#10-32 Thread
PART
NUMBER
http://www.mcmaster.com
© 2012 McMaster-Carr Supply Company
Information in this drawing is provided for reference only.
6516K11
Zinc-Plated Steel Right-Hand
Male-Threaded Connecting Rod
#10-32 Thread
1/4"
5/8"
5/16"
25° Max.
Ball Swivel
3/16"
7/16"
1 3/8"
1 1/16"
1/2"
Thread
Length
13/32"
5/16"
PART
NUMBER
http://www.mcmaster.com
© 2012 McMaster-Carr Supply Company
Information in this drawing is provided for reference only.
1064K711
Nylon Right-Hand Threaded
Ball Joint Rod End
+0.000
0.070" -0.020
3/4"
5/8" Usable Length
0.335"
-0.0015
3/16" -0.0065
+0.000
0.320" -0.020
0.029" Groove Width
PART
NUMBER
http://www.mcmaster.com
© 2012 McMaster-Carr Supply Company
Information in this drawing is provided for reference only.
92735A120
Grooved Clevis Pin
with Retaining Ring
+0.000
0.070" -0.020
1/2"
3/8"
Usable
Length
0.335"
-0.0015
3/16" -0.0065
+0.000
0.320" -0.020
0.029" Groove Width
PART
NUMBER
http://www.mcmaster.com
© 2012 McMaster-Carr Supply Company
Information in this drawing is provided for reference only.
92735A110
Grooved Clevis Pin
with Retaining Ring
1/4-20 Tapped Hole
.065
3.87
15.50
12.92
7.75
10.33
4X
.25
5.17
2.58
UNLESS OTHERWISE SPECIFIED:
DIMENSIONS ARE IN INCHES
TOLERANCES:
FRACTIONAL
ANGULAR: MACH
BEND
TWO PLACE DECIMAL
THREE PLACE DECIMAL
INTERPRET GEOMETRIC
TOLERANCING PER:
PROPRIETARY AND CONFIDENTIAL
THE INFORMATION CONTAINED IN THIS
DRAWING IS THE SOLE PROPERTY OF
<INSERT COMPANY NAME HERE>. ANY
REPRODUCTION IN PART OR AS A WHOLE
WITHOUT THE WRITTEN PERMISSION OF
<INSERT COMPANY NAME HERE> IS
PROHIBITED.
5
MATERIAL
NAME
DATE
DRAWN
TCA
4/3
CHECKED
MJW
4/3
Ballast tank
ENG APPR.
MFG APPR.
Q.A.
COMMENTS:
SIZE DWG. NO.
T6061-T6 Aluminum
USED ON
NEXT ASSY
APPLICATION
4
FINISH
A
stock
BTank_AL_hull
2
REV
A
SHEET 1 OF 1
SCALE: 1:8 WEIGHT:
DO NOT SCALE DRAWING
3
TITLE:
1
4.00
.08
UNLESS OTHERWISE SPECIFIED:
DIMENSIONS ARE IN INCHES
TOLERANCES:
FRACTIONAL
ANGULAR: MACH
BEND
TWO PLACE DECIMAL
THREE PLACE DECIMAL
INTERPRET GEOMETRIC
TOLERANCING PER:
PROPRIETARY AND CONFIDENTIAL
THE INFORMATION CONTAINED IN THIS
DRAWING IS THE SOLE PROPERTY OF
<INSERT COMPANY NAME HERE>. ANY
REPRODUCTION IN PART OR AS A WHOLE
WITHOUT THE WRITTEN PERMISSION OF
<INSERT COMPANY NAME HERE> IS
PROHIBITED.
5
MATERIAL
NAME
DATE
DRAWN
TCA
4/3
CHECKED
MJW
4/3
Tank Cap
ENG APPR.
MFG APPR.
Q.A.
COMMENTS:
SIZE DWG. NO.
6061 T6 Aluminum
USED ON
NEXT ASSY
APPLICATION
4
A
FINISH
BTank_AL_cap
2
REV
A
SHEET 1 OF 1
SCALE: 1:2 WEIGHT:
DO NOT SCALE DRAWING
3
TITLE:
1
male QC air line
1/4"
15.66
Total Length
1/4 NPT threaded
pipe for QC fitting
UNLESS OTHERWISE SPECIFIED:
DIMENSIONS ARE IN INCHES
TOLERANCES:
FRACTIONAL
ANGULAR: MACH
BEND
TWO PLACE DECIMAL
THREE PLACE DECIMAL
INTERPRET GEOMETRIC
TOLERANCING PER:
PROPRIETARY AND CONFIDENTIAL
THE INFORMATION CONTAINED IN THIS
DRAWING IS THE SOLE PROPERTY OF
<INSERT COMPANY NAME HERE>. ANY
REPRODUCTION IN PART OR AS A WHOLE
WITHOUT THE WRITTEN PERMISSION OF
<INSERT COMPANY NAME HERE> IS
PROHIBITED.
5
MATERIAL
6061 T6 Aluminum
USED ON
NEXT ASSY
APPLICATION
4
NAME
DATE
DRAWN
TCA
4/3
CHECKED
MJW
4/3
Ballast Tank
ENG APPR.
MFG APPR.
Q.A.
COMMENTS:
SIZE DWG. NO.
A
FINISH
BTank_Assemb
2
REV
A
SHEET 1 OF 1
SCALE: 1:8 WEIGHT:
DO NOT SCALE DRAWING
3
TITLE:
1
Pneumatics Diagram
Dimensions are in inches
Drawn:
MJW 4/15
Checked:
TCA 4/15
KG, KB, & GM (Submerged Prototype):
KGfp ≔ 0.132
Wfp ≔ 46.066
KGpop ≔ 0.0515
Wpop ≔ 24.821
KGbo ≔ 0.0775
Wbo ≔ 4.448
4 ⋅ Rtp
KGbfp ≔ Rtp + ―― = 0.073
3⋅
Rtp ≔ KGpop
~ Assuming ballast tanks
are half-filled with water
⎛⎝KGfp ⋅ Wfp⎞⎠ + ⎛⎝KGpop ⋅ Wpop⎞⎠ + ⎛⎝KGbo ⋅ Wbo⎞⎠
= 0.102
KGup ≔ ――――――――――――――
Wfp + Wpop + Wbo
3
Vpop ≔ 0.012
Vfp ≔ 0.019109
3
Vbo ≔ 0.0011
3
⎛ Vpop ⎞
υup ≔ Vbo + ⎜――
⎟
⎝ 2 ⎠
υup = 0.007
3
Iwpup ≔ 0
4
Iwpup
BMup ≔ ――= 0
υup
⎛
Vpop ⎞⎞
1 ⎛
KBup ≔ ――
⋅ ⎜⎛⎝KGbo ⋅ Vbo⎞⎠ + ⎜KGbfp ⋅ ――
⎟⎟ = 0.074
υup ⎝
2 ⎠⎠
⎝
GMup ≔ KBup − KGup + BMup = −0.028
GMup = −1.113
GMup
PercentHeightp ≔ ―――
= −0.099
0.285
Created with Mathcad Express. See www.mathcad.com for more information.
KG, KB, & GM (Submerged Full-Scale):
KGf ≔ 1.97
Wf ≔ 22530.2
KGpo ≔ 0.845
Wpo ≔ 11070
KGpa ≔ 2.1344
Wpa ≔ 4445.2
KGc ≔ 0.61
Wc ≔ 719.768
⎛⎝KGf ⋅ Wf⎞⎠ + 2 ⋅ ⎛⎝KGpo ⋅ Wpo⎞⎠ + 2 ⋅ ⎛⎝KGpa ⋅ Wpa⎞⎠ + 4 ⎛⎝KGc ⋅ Wc⎞⎠
KGu ≔ ―――――――――――――――――――
= 1.485
Wf + ⎛⎝2 ⋅ Wpo⎞⎠ + ⎛⎝2 ⋅ Wpa⎞⎠ + ⎛⎝4 ⋅ Wc⎞⎠
3
Vpo ≔ 4.283
Vpa ≔ 1.52911
3
Vc ≔ 0.06203
3
4 ⋅ Rt
KGbf ≔ Rt + ――= 0.57
3⋅
Rt ≔ 0.4
3
3
~ Assuming ballast tanks
are half-filled with water
⎛ Vpo ⎞
υu ≔ ⎜2 ⋅ ――
⎟ + ⎛⎝2 ⋅ Vpa⎞⎠
2 ⎠
⎝
υu = 7.341
Vf ≔ 0.29
Iwpu ≔ 0
4
Iwpu
BMu ≔ ――
=0
υu
⎞
Vpo ⎞
1 ⎛⎛
KBu ≔ ―⋅ ⎜⎜KGbf ⋅ 2 ⋅ ――
⎟ + ⎛⎝KGpa ⋅ 2 ⋅ Vpa⎞⎠⎟ = 1.222
υu ⎝ ⎝
2 ⎠
⎠
GMu ≔ KBu − KGu + BMu = −0.264
GMu = −10.38
GMu
PercentHeight ≔ ――――――
= −0.092
2.25 + 0.61
Created with Mathcad Express. See www.mathcad.com for more information.
ρ ≔ 63.989 ――
3
ID ≔ 3.87
Inside Pontoon Length
Lc ≔ 2.625 = 31.5
g ≔ 32.2 ―
2
Draft
t ≔ 2.1
OD ≔ ID + 2 T = 4
OD
r ≔ ――
= 0.167
2
r (ϕ − sin (ϕ))
At ≔ ―――――= 0.046
2
VTotal ≔ 2 ⋅
VMaterial ≔ 2 ⋅
Depth in Pontoon
d≔0
ID
r' ≔ ――
= 0.161
2
⎛
⎛ (r − t) ⎞⎞
ϕ ≔ 2 ⎜acos ⎜―――
= 3.242
⎝
⎝ r ⎟⎠⎟⎠
2
Pontoon Thickness
T ≔ .065
⎛
⎛ (r' − d) ⎞⎞
=0
ϕ2 ≔ 2 ⎜acos ⎜―――
⎝
⎝ r' ⎟⎠⎟⎠
2
r ⎛⎝ϕ2 − sin ⎛⎝ϕ2⎞⎠⎞⎠
Ad ≔ ――――――
=0
2
2
2
⎞
⎛ (ID) 2
ID
L
T
⋅
⋅
−
――
――
⎜
⎟ = 0.428
c
4
⎝ 4
⎠
2
3
*Calculated with one bulkhead, 2 flat caps
⎞
⎛ ⎛⎝OD 2 − ID 2 ⎞⎠
2
3
⋅ Lc + OD ⋅ T⎟ = 57.158
⎜―――――
4
⎝
⎠
WPVC ≔ 5.619 ―
WPontoons ≔ VMaterial ⋅ 168.56 ――
= 5.576
3
WTotal ≔ ⎛⎝WPontoons⎞⎠ + 9.39
*Aluminum Density = 168.56
= 14.966
FB ≔ ⎛⎝ρ ⋅ 2 ⋅ ⎛⎝At − Ad⎞⎠ ⋅ Lc − WTotal⎞⎠ = 0.626
Created with Mathcad Express. See www.mathcad.com for more information.