Biomimetic Crab - P11029
Technical User’s Manual
Designed, Built, and Tested by:
Bill Dwyer, Joe Mead, Shaynae Moore, Casey O’Connell
Kate Gleason College of Engineering
Rochester Institute of Technology
James E. Gleason Building
77 Lomb Memorial Drive
Rochester, NY 14623-5603
https://edge.rit.edu/content/P11029/public/Home
February 18, 2011
Rev. A
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Biomimetic Crab - P11029
TABLE OF CONTENTS
Chapter 1 – Introduction
....................................................................................................... 4
1.1 Background information ..................................................................................................................... 4
1.2 Overview of Project ............................................................................................................................. 4
1.3 Objectives of Manual ........................................................................................................................... 4
Chapter 2 – McKibben Air Muscles
........................................................................................ 5
2.1 Theory ................................................................................................................................................... 5
2.2 Performance Characteristics ............................................................................................................... 6
2.3 Construction ......................................................................................................................................... 8
2.4 Detailed Drawings ............................................................................................................................... 9
2.4.a End Cap 1 ............................................................................................................................... 9
2.4.b End Cap 2 ............................................................................................................................. 10
2.5 Muscle Assembly Drawings ............................................................................................................. 11
Chapter 3 – Design Considerations ....................................................................................... 12
3.1 Concept Selection............................................................................................................................... 12
3.2 Detailed Design .................................................................................................................................. 13
3.3 Detailed Drawings ............................................................................................................................. 18
3.3.a Body ..................................................................................................................................... 18
3.3.b Shell ...................................................................................................................................... 19
3.3.c Umbilical Mount ................................................................................................................. 20
3.3.d Front..................................................................................................................................... 21
3.3.e Claw ..................................................................................................................................... 22
3.3.f Pincher .................................................................................................................................. 23
3.3.g Forearm ............................................................................................................................... 24
3.3.h Leg........................................................................................................................................ 25
3.3.i Leg Bracket ........................................................................................................................... 26
3.3.j Step Connector ..................................................................................................................... 27
3.4 Assembly Drawings .......................................................................................................................... 28
3.4.a
3.4.b
3.4.c
3.4.d
Claw ..................................................................................................................................... 28
Leg ........................................................................................................................................ 29
Crab ...................................................................................................................................... 30
Bill of Materials .................................................................................................................. 31
Chapter 4 – Controls
........................................................................................................... 32
4.1 Equipment/Software Required ........................................................................................................ 32
4.2 USB SSR24 MCC Control Relay Board ........................................................................................... 32
4.3 NVZ3140 Single-Action Solenoid Control Valves ......................................................................... 32
4.4 Interface ............................................................................................................................................... 32
4.4.a Logic ..................................................................................................................................... 33
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Biomimetic Crab - P11029
4.4.b Architecture .......................................................................................................................... 33
4.5 Block Diagram .................................................................................................................................... 33
4.5.a Logic ..................................................................................................................................... 33
4.5.b Architecture .......................................................................................................................... 34
Chapter 5 – Integration ........................................................................................................ 35
5.1 Assembly Requirements ................................................................................................................... 35
5.2 Assembly Protocol ............................................................................................................................. 35
5.3 Connecting Muscles .......................................................................................................................... 35
5.4 Connecting the Umbilical Cord ....................................................................................................... 38
5.5 Connecting the Controls ................................................................................................................... 39
Chapter 6 – Operation
......................................................................................................... 42
6.1 Start-up & Test Software Requirements ......................................................................................... 42
6.2 Running the Crab............................................................................................................................... 43
Chapter 7 – Troubleshooting
............................................................................................... 44
7.1 Pneumatic Muscle .............................................................................................................................. 44
7.2 Assembly............................................................................................................................................. 44
7.3 Controls ............................................................................................................................................... 45
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Biomimetic Crab - P11029
Chapter 1 – Introduction
1.1 ....................................................................................................................................................... Backgr
ound information
For the past several years, Dr. Lamkin-Kennard has sponsored senior design projects to showcase
the McKibben air muscles. Previous projects have included modeling human joints (hands, elbows, and
wrists), characterization of air muscles, and control system for air muscles. Our Project is an extension of
these previous examples. The team consists of four mechanical engineers Casey O’Connell, Bill Dwyer,
Joe Mead, and Shaynae Moore. The team’s consultant is Bill Nowak a Principal Engineer at Xerox
Corporation. The customer and primary sponsor is Dr. Kathleen Lamkin-Kennard, a professor in the
Mechanical Engineering program at RIT.
1.2 ....................................................................................................................................................... Overvi
ew of Project
The overall assignment is to design, build and test a Biomimetic Crab that can operator
underwater. The crab must be actuated by pneumatic air muscles and controlled using a LabView GUI.
Project Scope/Objectives
1)
Produce an Underwater Biomimetic crab to showcase Dr. Lamkin-Kennard’s research using the
McKibben air muscles.
2)
Explore the feasibility of using the McKibben air muscles in an underwater environment for
surgery within a body and for dexterous work in underwater applications.
Deliverables
1)
A functional Biomechanical crab that achieves underwater claw and pincher movement using
the McKibben air muscles
2)
Complete and organized “user’s manual” clearly explaining design, construction, and, operation
of the final product
Expected Benefits
If deliverables are satisfied this project will be used to show that underwater implementation of
McKibben air muscles can be used in underwater applications. This will hopefully lead to additional
research opportunities and further the work Dr. Lamkin-Kennard. In addition, the crab will be a
demonstration piece for events such as the innovation festival to spark the imagination of younger
audiences to consider science, technology and engineering.
1.3 ....................................................................................................................................................... Objecti
ves of Manual
The objective of this manual is to clearly convey the thought process, product construction and
assembly order in regards to the robotic crab. Also included are the control logic and architecture of the
LabView platform and GUI. A troubleshooting section of resolved issues should field miscellaneous
problems and concerns.
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Chapter 2 – McKibben Air Muscles
2.1 Theory
Pressure
Tension
From Chou and Hannaford [1]
Governing Equations (Assuming Perfect Cylinder)
D0 
2
b
n
L final  b * cos( final )
n = number of turns
Muscle Wrapped
b = complete length of thread
x
Through substitution…
Muscle Unraveled
F
 * Pgage * D0 2
4
x
θ
(3 cos ( initial )  1)
2
b
L
n*π*D
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Biomimetic Crab - P11029
The pneumatic muscle is a complex non-linear system and can be described with respect to its
constituents. Theoretical modeling with cylindrical approximation and energy conservation was applied
similar the aforementioned setup. Where V is volume, F is force yield of muscle, P’ is input pressure, θ is
braid angle of mesh, and L is the muscle length the following relationship is used to describe the physical
state of the muscle. Because the calculated force defers with respect to two differentials (dv/d θ) and
(dL/dθ) at any given instant during its transient movement you may not know the length or the braid
angle associated with expected muscle output.
Due to time constraints in MSD1 explicit testing will occur for the main purpose of characterizing
specs for the muscles that we plan on using in our Crab design. Overall Change in length will be
recorded with a spring gauge for loads less than 7 lb. In order to choose muscles appropriate for our
design, we will select from a group of tested muscles from past years. The trends previously discussed
will help us narrow down what properties of the muscles will yield the best results. Our muscle choice
will be oversized in order to fully accommodate the claw system. The muscle from empirical research
conducted by group P08024 was considered. Our muscle choice is a deviation from the muscle used in
our prototype. Forwardly thinking, with a 7” muscle, we may operate the claw at lower psi values and
still achieve a significant change in length. We have oversized our muscle so our claw may operate
within a range of its performance domain. The specific muscle we choose is 7” length, with outer
diameter of 5/16” and a surgical wall thickness of 1/32“.
Furthermore, results from experimenters in the Kate Gleason Mechanical Engineering Lab show
that for smaller muscles, even when it is possible to develop a theoretical model, a muscle will likely and
noticeably deviate from its expected behavior. The Senior Design team found that in application it is
better to use theoretical models as a heuristic for guided experimentation. Since muscle behavior is
highly repeatable, by testing a group or class of muscles an exact definition of a muscle can be produced
for design. In the case of the product development situation this process is warranted and much more
fruitful and time efficient.
2.2 Performance Characteristics
Data was produced using pseudo static loading configuration and was tested using muscles with
the following specifications. These results were published in an ASME journal and are authored by Curt
S. Kothera, Mamta Jangid, Jayant Sirohi, Norman M. Wereley of the University of Maryland 2010.
Muscle Specs: 8” Length, 3/8” Inner Diameter,
½” Outer Diameter, Braid Angle 42.9°
Number of turns: 108
Muscle 3c Blocked Force vs. Pressure
Experimental Data
Muscles produce considerable tension and vary linearly with
the pressure that they are subjected to.
>> Beneficial to use high PSI.
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Biomimetic Crab - P11029
Muscle Specs: 4”,6”,8” Lengths, 3/8” Inner Diameter,
½” Outer Diameter, Braid Angle 42.9°
Number of turns: 108
Muscle 4c Blocked Force vs Actuator Length
Kept at constant pressure and diameter, it can be seen that the
length of a muscle has very little bearing on the force it is
capable of producing.
>>Length has no bearing on adding Force .
Muscle Specs: 8” Length
1/8”,1/4”,3/8” Inner Diameters
Muscle 2,3,4 c Blocked Force vs Actuator Diameter
Tested at constant pressures and length, it can be seen that the
Diameter of a muscle yields a quadratic increase in the force it is
capable of producing. It should also be noted that a benefit is
realized at much larger diameters and higher Pressures. Inner
Diameter is used in this example.
>>Choose surgical tubing with the largest diameter.
Muscle Specs: 8” Length, 3/8” Inner Diameter,
½” Outer Diameter, Braid Angle 42.9°
Number of turns: 108
Muscle 3c Free Contraction vs Pressure
Experimental Data
Muscles length changes dramatically at higher pressures.
Quadratic Relationship
>> Beneficial to use high PSI.
Muscle Specs: 4”, 6”, 8” Lengths, 3/8” Inner Diameter,
½” Outer Diameter, Braid Angle 42.9°
Number of turns: 108
Muscle 4 a,b,c Free Contraction vs.
Length Experimental Data
Longer muscles have quadratic behavior in the amount in
which they are able to contract. Longer muscles are
continually increasing their contractile range.
>>Original muscle Length is the critical determining
factor in creating displacement during a muscle stroke.
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Biomimetic Crab - P11029
From Group P08024 past project work
For this data set, a test was run using a pulley system and a potentiometer. The above data
reflects free contraction, which means there was no load placed on the other end of the muscle and it was
allowed to assume a full range of contraction. As load is placed on the other end of the muscle the load
pulls on the muscle making it longer and prohibits free contraction. You may see this in the research
paper. A trend that also can be seen and is important to point out, there is very little diminished length at
lower force loads. We hope to operate at these lower loads by selecting the right spring constant in order
to reap the full benefit of the displacement that Muscle C exhibits.
2.3 Construction
The air muscles are a simple assemble of two end caps, two end claps, eyelet, quick connect for
the air hose, silicone tubing, and nylon mesh hose. Note the inner diameter of the silicone tube should
be approximate 10-20% smaller than the end caps. Also, the nylon and silicone tubing should have the
same length
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Biomimetic Crab - P11029
2.4 Detailed Drawings
2.4.a End Cap 1
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2.4.b End Cap 2
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2.5 Muscle Assembly Drawing
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Chapter 3 – Design Considerations
3.1 Concept Selection
In order to meet the form and function of our final product we complied the requirements from
the Project Readiness Package and follow up customer interviews to create the customers needs.
Rev #1.3
Engr.
Spec. #
Customer Needs (description)
System
Importance
CS1
Device must use McKibben muscle technology
5
CS2
Device must function underwater
CS3
Pinchers perform and mimic a crab’s pinching movement
CS4
Crab’s wrist performs and mimics flexion and extension
CS5
Must have thorough documentation
CS6
Single, unified umbilical cord attachment
CS7
CS8
Device gives overall impression of a crab
Functionality of the device must be enabled through a
control system
Claw
Umbilical Cord Claw
Aesthetics
Claw
Claw
Documentation
Umbilical Cord
Aesthetics
CS9
Claws must operate independently of each other
CS10
Pinching speed must be greater than wrist speed
5
5
5
5
3
3
3
Control Interface
1
Claw
Claw
1
In order to make a quantifiable analysis of the customers’ needs engineering specifications chart
Note: Documentation was raised in importance per
was created. Customer Request at Initial Design Review
Engr.
Spec. #
Specification (description)
System
ES1
length of umbilical cord
ES2
diameter of umbilical cord
ES3
flexibility of umbilical cord
ES4
# of airlines in umbilical cord bundle
Umbilical cord
Umbilical cord
Umbilical cord
Umbilical cord
ES5
input pressure of McKibben Muscles
Claw
Unit of
Measure
Marginal
Value
Target
Value
ft
6
8
Single unified umbilical cord attachment
in
< 2.5
<2.0
Single unified umbilical cord attachment
yes/no
no
yes
Single unified umbilical cord attachment
#
10
7
psi
40
60
lb
5
10
Customer Specification
Single unified umbilical cord attachment
Device uses McKibben muscle technology
Device must function underwater
ES6
output force of McKibben Muscles
Claw
ES7
length of McKibben Muscles
Claw
Device uses McKibben muscle technology
Device must function underwater
Pincher performs and mimics a crab's pinching movement.
Device uses McKibben muscle technology
Device must function underwater
Pincher performs and mimics a crab's pinching movement.
ES8
speed/velocity of pincher
Claw
Speed must be greater than wrist speed
Pincher performs and mimics a crab's pinching movement.
Claw
Crab's wrist preforms and mimics flexion and extension.
ES9
range of motion of flexion
ES10
speed/velocity of wrist movement
Claw
ES11
incremements of motion
Claw
ES12
height of chassis from ground surface.
ES13
weight of crab
ES14
width of crab abdomen
ES15
height of legs
ES16
length of crab body
ES17
# of legs
ES18
portability
ES19
USERS MANUAL (assembly & operation)
ES20
USERS MANUAL (maintain & storage)
ES21
DECISION MAKING PROCESS (organized compilation)
ES22
User interface to control device
Speed must be less than pincher speed
Device gives overall impression of crab.
Functionality of device must be enabled through a control system
Device gives overall impression of a crab
Comments/Sta
Long enough to reach bo
Depends on the # of
Is it flexible enough to allow for
Depends on whether robo
Enough force to oppose resistan
in
4
7
cycles/min
60
80
Length will vary based on ra
1 cycle = open &
degrees
45
90
angular displacem
cycles/min
< pincher
30
1 cycle is moving from neutral to f
degrees
90
45
1 displacement in flexion
Body / Chassis
Body / Chassis
Body / Chassis
Body / Chassis
Body / Chassis
Body / Chassis
Body / Chassis
Device gives overall impression of crab
in
--
--
Device gives overall impression of crab
lb
--
--
Device gives overall impression of crab
in
--
--
Device gives overall impression of crab
in
--
--
Device gives overall impression of crab
in
8
10
Length specified to accommod
Device gives overall impression of crab
#
3
4
Model has 3 sets of legs + set o
yes/no
yes
yes
Can it be moved from place to place eas
Documentation /
Control Interface
Documentation /
Control Interface
Must have thorough Documentation
Functionality of the Device must be used through a control system
time (hr)
1.25 hrs
1
Can an RIT student with no prior knowle
operate our device in a timely fasion with
manual.
Must have thorough Documentation
time (min)
30
15
Must have thorough Documentation
yes/no
yes
yes
Can an RIT student or faculty member tra
our device
timelyt
Functionality of the Device
mustinbea used
Can Dr. Lamkin Kennard clearly unders
organized and compiled data, tests and
and limitations
of ourt
Functionality of the Device
must be used
# Commands
12
10
Control interface is not overly comple
command options for all the different mo
Documentation /
Control Interface
Documentation /
Control Interface
Functionality of the device must be enabled through a control system
Functionality of the device must be enabled through a control system
Claws must operate independently of each other
Ratios of height, width, and height of le
those of a realistic looking crab. Act
important, and will ultimately be determ
needed to ensure func
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Biomimetic Crab - P11029
After the customer needs were turned into specifications it was important to begin
brainstorming ideas of how we were going to satisfy each need through a Pugh Chart. Through this chart
we were able to choose the best concept and begin detailed design.
3.2 Detailed Design
Once the conceptual design of the crab was finished, a solid model drawing was created using
SolidWorks. This model allowed the conceptual design to be tweaked in order meet to the engineering
specifications. The geometry and layout of the design was finalized based on the muscle selection.
Calculations for spring and muscle force were used to validate the design geometry of the crab to ensure
full functionality before manufacturing began. Section 3.3 has all the parts required to assemble the crab.
In section 3.4 there are exploded assembly drawings which show the proper construction layout. Parts
were sent out to local machine and rapid prototyping shops.
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Claw Geometry and Force
Displacement required for 30, 45, 90 degrees:
 We used a ½ inch level arm in order to hide control wires and springs while still maintaining the
correct proportions of the real crab.
 1.5 inch from the pivot point, is the pulley that guides the control wires.
 Simple geometric model was used to calculate angles at each position.
 The neutral position is assumed to be 90 degree between the lower claw surface and the inside
forearm surface.
 The Muscle must deflect 2 times the contracted length. Slack length must be incorporated to
allow full range of motion.
Deflection Required for Claw Rotation
Claw Rotation
degrees (+/-)
Muscle Deflection
Slack Deflection
FOS (1.8”)
30
45
90
inches
0.25
0.379
0.58
inches
0.5
0.758
1.16
3.6
2.4
1.6
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Force Calculation required for 30, 45, 90 degrees:
 The spring used for this calculation is specified in the Bill of Materials and it has a spring
constant of 3.4 lbf/in and deflected by ¼” at the neutral position (left side of above diagram)
 The deflections were used to calculate the spring for each of the positions.
 A simple force balance equation was used to solve for the necessary muscle force. Sum of forces
in the x and y direction as well as sum of torques around the pivot point.
 Friction was ignored for force calculations because washers and free spinning pulleys are used in
the design.
Force Required for Claw Rotation
Claw Rotation
degrees (+/-)
Muscle Force
lbf
FOS (20 Lbf)
30
45
1.65
2.14
12.1
9.3
90
Infinite
N/A
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Biomimetic Crab - P11029
Pincher Geometry and Force
Displacement required for 30, 45, 90 degrees:
 We used a 0.7 inch level arm in order to hide control wires and springs while still maintaining
the correct proportions of the real crab.
 2.65 inch from the pivot point, is the pulley that guides the control wires.
 Simple geometric models were used to calculate angles at each position.
 The neutral position is assumed to be 90 degree between the lower claw surface and the inside
pincher surface.
 The pincher used one muscle in a single direction, directly opposed by a spring
Deflection Required for Pincher Rotation
Claw Rotation
degrees (+/-)
Muscle Deflection
inches
FOS (1.8")
30
45
90
0.37
0.53
0.79
4.9
3.4
2.3
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Biomimetic Crab - P11029
Force Calculation required for 30, 45, 90 degrees:




The spring used for this calculation is specified in the Bill of Materials and it has a spring
constant of 2.15 lbf/in and deflected by ¼” at the neutral position (left side of above diagram)
The deflections were used to calculate the spring for each of the positions.
A simple force balance equation was used to solve for the necessary muscle force. Sum of forces
in the x and y direction as well as sum of torques around the pivot point were calculated.
Friction was ignored for force calculations, washers and free spinning pulleys are used in the
design.
Force Required for Pincher Rotation
Claw Rotation
degrees (+/-)
Muscle Force
FOS (20 Lbf)
lbf
30
45
0.78
1.14
Infinite
90
25.6
17.5
N/A
* IMPORTANT* All Drawings and Assemblies are provided on the USB Thumb Drive.
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3.3 Detailed Drawings
3.3.a Body
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3.3.b Shell
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3.3.c Umbilical Mount
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3.3.d Front
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3.3.e Claw
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3.3.f Pincher
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3.3.g Forearm
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3.3.h Leg
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3.3.i Leg Bracket
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3.3.j Step Connector
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3.4 Assembly Drawings
3.4.a Claw
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3.4.b Leg
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3.4.c Crab
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Biomimetic Crab - P11029
3.4.d Bill of Materials
Item Discription
Abrasion-Resistant Clear Polyurethane Tubing
Abrasion-Resistant Clear Polyurethane Tubing
Stainless Steel Socket Head Cap Screw
Stainless Steel Hex Nut
Silicon Flexible Tubing
Nickel-plated Brass Push-to-Connect
Clear Polyureathane Tubing
Stainless Steel Screws Head Cap Screw
Stainless Steel Screws Flat Washer
Stainless Steel Screws Lock Washer
316 Stainless Steel Thin Hex nut
Stainless Steel Extension Spring 1 1/4"
Stainles Steel Extension Spring 1 1/2"
Abrasion-Resistant Clear Polyurethane Tubing
Spiral Cable Wrap
Demonstration Kiddie Pools
Clear Plastic Storage Container
Rapid Prototype Leg Mounts
Rapid Prototype Leg Visor
Gate Valves Solonids
15 lb Fishing Line
2' x 2' Aluminum Sheet
Muscle Materials
Plastic Dowl
Nickel Plated Brass Push-to-Connect
Velcro Adhesive
Acrylic Mounting Bracket
Acrylic Baseplate
Shell
Size
1/8"
1/16"
4-40 Thread
4-40 Thread
0.25"
1/4" Fitting
1/16" ID
4-40 Thread
18-8
18-9
7mm
3/16"
5/16"
3/32"
5 ft
3' , 5'
32 Qt
Dwg
Dwg
15lb
1/8" Thck
Various
.625"
1/8"
0.5"
Dwg
Dwg
Custom
Bill Of Materials
Quantity
Related Component
25 ft
Umbilical Cord
25ft
Umbilical Cord
1
Arm Assembly
1
Arm Assembly
10 ft
Muscle Rubber
5
Umbilical Mount
50 ft
Umbilical Cord
1
Body Assembly
1
Body Assembly
2
Body Assembly
1
Body Assembly
1
Arm Assembly
1
Arm Assembly
25ft
Umbilical Cord
1
Umbilical Cord
1
Environment
1
Hardware Envelope
8
Leg Assembly
1
Front Visor
6
Controls
2'
Tendon Actuators
1
Arm and Leg Assembly
Muscles
2'
Umbilical Assembly
12
Umbilical Assembly
1ft
Shell Mount
1
Umbilical Mounting Bracket
1
Baseplate
1
Shell
Vendor/Acquisition Method
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
MSC
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
McMaster-Carr
RadioShack
Toys 'R' Us
Target
Brinkman Lab
Brinkman Lab
Allocated by ME dept.
Allocated by ME dept.
Allocated by ME dept.
Allocated by ME dept.
Allocated by ME dept.
Allocated by ME dept.
Allocated by ME dept.
Allocated by ME dept.
Allocated by ME dept.
Fine Line Prototyping
Total
Cost
$7.50
$11.50
$4.00
$2.75
$8.50
$17.20
$11.50
$7.50
$2.00
$0.87
$4.69
$10.02
$13.12
$7.50
$4.99
$21.98
$7.99
$200.00
$143.61
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Chapter 4 – Controls
4.1 Hardware/Software Requirements








Computer
LabView 8.6 Software
USBSSR24 MCC Control Relay Board
NVZ3140 Single-Acting Solenoid Control Valves
24V Power Source
9 V Power Source
USB Cable
Air Supply Line
4.2 USB SSR24 MCC Control Relay Board
This is a 24 port relay control board that communicates directly with the computer. A lot of the
equipment and materials for this project have been from projects that are now obsolete. With a limited
budget some materials took precedent over others for purchasing. So, despite the system only needing 6
control ports, a 24 port relay board was readily available and free. There is a 24 volt power source wired
into it for the solenoid controller which is discussed in further detail in Section 3.2. The board itself it
powered by a 9 volt power source, and communication occurs through a USB cable.
4.3 NVZ3140 Single-Action Solenoid Control Valves
The operation of the solenoid controller pressurizes on control activation and depressurizes when
the control is deactivated. Its pressure input range is approximately 22 psi to 102 psi. The maximum
pressure input for the system is 60 psi, and should NOT go above this pressure per the customer request.
4.4 Interface
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4.4.a Logic
The interface was designed in such a way that any age user can control the movement of
the crab. It allows the user to be interactive with the system, which contributes to the fun factor
requested by the customer.
4.4.b Architecture
The interface is a combination of customized controls and indicators. The background is
a jpeg image of the CAD model, with the “dynamic” elements removed. This could simply be
done by suppressing chosen parts in CAD and saving it as a jpeg image. As controls and
indicators were added to the program they each were customized also using jpeg images of
roughly the same size. Making the images the same size was very important in making the
interface dynamic. When the user is activating or deactivating the controls, they change color
state (not size); red for off and green for on. Using images only gives the illusion that the
interface is dynamic. Once the controls and indicators were all customized they were
embedded into their respective places on the interface image and locked in so that the user will
not be able to move them around. A stop button was added in place of the abort button
removed from the toolbar. Sudden abortion can cause communication failures to the relay
board if the user tries to rerun the program again.
4.5 Block Diagram
4.5.a Logic
The block diagram was composed in such a fashion that if in the future it is improved,
one can easily understand the structure after spending a little time familiarizing with LabView
software.
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4.5.b Architecture
There are six user controllers and indicators, which are also embedded in the front panel.
To prevent communication failures or mechanical damaging of the system, case structures are
implemented. They inhibit the user to be able to activate the extension and flexion function for
each wrist simultaneously. As mentioned previously, this can cause system damage. However,
if the user chooses to flex the right wrist and extend the left, he or she can do so. The controls,
indicators, and board communicator vi are encompassed in an event structure that has two
cases. The first case is a “value change” that says do not execute until a control is activated.
This keeps the program from constantly checking whether or not a control has been activated.
The second case for the event structure is a “stop” command. In case the user needs to abort the
program for any reason, they can just simply press the stop button on the front panel. The final
encompassing structure is the while loop, which is designed to keep the program running
continuously allowing the removal of the abort button on the front panel toolbar. Also, it keeps
the program in the run continuously state when loaded.
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Chapter 5 – Integration
5.1 Assembly Requirements












One Shell
One Front
One Body
One Umbilical Cord Mount
Six Step Connectors
Two Crab Assemblies
Eight Leg Assemblies
34 - ½” 4-40 Screws
16 - 1” 4-40 Screws
24 - 4-40 Washers
34 - 4-40 Nuts
Appropriate pneumatic connect pieces
o 1/32” hose
o ¼” hose
o 12 - 1/32” hose connectors
o Six 1/32” Solenoid Connections
o Six ¼” hose connectors
5.2 Assembly Protocol
After all parts and hardware is acquired reference section 3.4 to see how parts fit together. It is
important that all parts are built to spec and the appropriate hardware is used. Please refer to the
SolidWork’s drawings and assemblies for further guidance.
5.3 Connecting Muscles
After the crab is fully assembled the muscles need to be connected to the appropriate position.
The muscles should be tied to the claw control screws using at least 15 pound test fishing line. The control
ends should be doubled by creating a simple slip knot. Then the two loss ends should be tied in a double
half hitch. When attaching muscles it is crucial that apposing muscle have enough slack to allow motion
in the opposite direction.
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Slip Knot
http://www.lake-link.com/anglers/knots/knotdetails.cfm?knotID=10
Double Half Hitch
http://blog.lindenhurstmartialarts.com/
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Here are a few pictures to show how the claw should be connected. The left and right arms are
symmetric meaning the assemblies are equally and except mirrored over the centerline.
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5.4 Connecting the Umbilical Cord
The Umbilical cord should be label at both ends from one to six. The solenoid and umbilical cord
mount on the crab should be labeled one through six as well. Simply match up the numbers to their
corresponding valve and the crab should be ready to operate. See the pictures below for an example of
a correct connection.
Solenoid
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Umbilical Cord Mount on the Crab
5.5 Connecting the Controls
Similar to the pneumatics all the control wires are number for quick reference. It is important that
the air, 9 volt, 24 volt and USB cables are connected into the electronics before the wall/computer.
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Then ensure that the relay and solenoid are wire correctly to each other.
In order to power the solenoids make sure the 24 volt power source is wired to the relay and the
ground terminal.
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The make sure the regulating valve on the air line is limited to approximately 45 psi and connect
the air line into the solenoid.
At this point it is safe to plug in the 9 and 24 volt power sources and connect the USB to the
computer.
*IMPORTANT* Wait until after the software is tested before the air is turned on.
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Chapter 6 – Operation
6.1 Start-up & Test Software Requirements

MCC DAQ Inscal32
Once the Inscal32 program is started, right click on the board listed and then press “flash L.E.D.”
make sure the USB L.E.D. light is on and flashes. If the LED does not flash remove it and then reconnect.
After the light flashes, click on the test tab and click the digital option. Then you should be able to
run a digital test of the relay board. Press “run test” Watch the relay board and make sure that all L.E.D.’s
light up for each of the 24 ports. If both of these tests run successfully start LabView. If both of these tests
run successfully start LabView. Otherwise refer to Section 7.3
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
LabView 8.6
o
RoboCrab_Final.Vi
Open LabView then open RoboCrab_Final.Vi. The crab is 100% function and will move to the
inputs of the front panel.
* IMPORTANT* The MCC DAQ and LabView.Vi are available on the USB Thumb Drive provided.
6.2 Running the Crab
The LabView interface allows each of the muscles to be called on command. As muscles are
called resulting actions and movements are performed. Each arm of the crab has been logically
programmed so movement can occur independently. Program algorithms can be run by clicking the
icon representing desired movements. On each hand two muscles pairing relationships can be
observed. Pinching can be performed by the ‘Upper Claw’ button, which will latch and fire the muscle
responsible for clenching. This muscle can be fired independently and in parallel with mobile wrist
options. The wrist has a muscle pairing arrangement that either allows for wrist abduction or wrist
adduction. Analog logic can be toggled by clicking on the abduct command ‘Inner Wrist’ or adduction
command ‘Outer Wrist.’ Between the commands listed on the LabView GUI each claw is capable of
three degrees of freedom.
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Chapter 7 – Troubleshooting
7.1 Pneumatic Muscle
Since the pneumatic muscles are used in an underwater environment, minimizing leaks and
escaping air is a critical concern. The visibility of leaks is more prominent underwater and occurred for
our muscles during a performance test. The best strategies to minimize leaks rest in the assembly of the
pneumatic muscles. The following features led to the best results.
1.
When constructing the muscle, the rubber surgical tubing is pulled over the plastic end
plug and the plastic air diffuser. It is critical that the rubber tubing is pulled completely up
and covers all plastic material of the spindle. For a further robust seal, tape was wrapped
around the tubing any remaining exposed plastic.
2.
The clamps must be tightened with screwdriver completely. It is important to stress
that they should be over tightened and many leaks can be avoided by rechecking over
these components.
3.
The actuators need to expand in order to create movement.
Cleanly ordering these
muscles and constraining the muscles along a relegated path may increase performance. In
an attempt to decrease interaction electrical tape has been wrapped around the protruding
clamps and any non-smooth muscle surfaces.
7.2 Assembly
Regarding the functionality of the device there are a few factors that can impact the performance
of the robotic crab. The machine design of interfacing parts contributes highly to the performance
features of our final design. Listed here are critical assembly characteristics.
1.
“Tendon” alignment is critical to the functionality of the crab. The pneumatic muscle will
contract an arbitrary amount with a given input pressure. The tendon that connects to an
appendage lever should allow the full muscle to pull upon a lever completely. Tendons are
critical because they can be factors that decrease the degree of freedom and range of
motion. In our project reinforced 7lb fishing line was used to connect to the skeletal
appendages. Tendons must be tied and aligned so that they are not too loose.
2.
Appendage Interaction is held in proper alignment by locking nuts and brass washers. The
brass washers drastically decrease friction of the two aluminum surfaces. It is important
that friction and grinding is kept to a minimum between the moving surfaces so that
muscle contraction is not impeded. The lock nuts being tightened up forces the mechanical
arms to be parallel and properly aligned.
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7.3 Controls
The controls system is very important component that integrates communication and movement,
with communication between the software and relay system being the forefront. The program has
program has been designed on an older computer model and in Labview 2009. Below are some tips
optimal for operation of the controls.
1.
In the event the software program is not communicating with the relay board & solenoid gate
valves refer to section 6.1. If this is not effective than exit the program and reload it. Upon
reloading activate a muscle to check for movement. If this is still ineffective then the computer
must be restarted.
2.
If the LEDs failed to light up as indicated in section 6.1, then use the follow instructions to
troubleshoot. There may be a faulty connection in the wires from the solenoid controller to the
relay board. Ensure that all the wires are properly connected to their respective ports. There are
numbers on the wires as well as the relay board for match ups. Repeat the “run test” phase. If the
LEDs turn on then proceed to section 6.2. Otherwise, remove the connection for non-operational
gate valve and test with a power source. Before doing this exit out of the program and disconnect
all live power sources. In the event that there is still failure after testing the faulty valve, replace
with a new one.
3.
This section discusses troubleshooting the MCC relay board. The user will always be able to tell
whether or not the output signal from the computer is being sent to and output by a port on the
MCC board. The LEDs will light red when this occurs. This means there are not any defects in the
board. After it has been determined that communication from the computer to the board is not
the issue (Section 7.3.1) and the indicators do not light the three following options can be
executed. They should only be performed by an individual that already has an idea of what they
are doing.
LED Indicator
Red when
on/working
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(A) Disconnect all live power sources and exit the software program. Remove the top cover to
the relay board by removing the screws. You will need a screwdriver to do this. There are
relays (red square boxes) for every port. Remove the relay for the non-function port and
replace. Test to check functionality before reattaching the hub.
(B) Replace the entire MCC relay board and rewire using the following image. Only use ports 06 (according to labeling) for wiring the solenoid controller and controller power source. The
controls system will not work if wired into any other ports on the board. The power source
for the solenoid controller is wired into port 0.
(C) The solenoid controller can be wired into other ports on the board, but the code in the block
diagram will have to be altered. The following picture is a circuit diagram of the board. The
port name is the important information to be gathered because the port name in the
Labview block diagram must correspond with the ports the controller is wired into.
Otherwise the controls system will not work.
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REPLACING OR REMOVAL OF ANY MCC RELAY BOARD COMPONENTS SHOULD BE A LAST RESORT AS IT
CAN BE COSTLY IF NOT AVAILBLE IN THE DEPARTMENT. THE USER’S MANUAL ONLINE CAN BE
REFERRED TO FOR ANY INFORMATION NOT LISTED HERE.
http://www.mccdaq.com/PDFs/Manuals/USB-SSR24.pdf
If any hardware has to be reassembled check for air leakage before operation. The system may not
perform optimally otherwise. Plumber’s tape may be needed to reseal joints. Gently pull on the air
tubing to ensure lock tight connection into fast connects.
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