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Project Goals To create a computer simulation of the kinematics
of an air muscle-controlled human joint (the elbow) Build a prototype joint to compare to and improve
the computer model Make end product adaptable and useful for future
iterations
Team Roles Casey
Math TheoryPneumaticsArm DesignArm
FabricationEDGE
ArthurControls
SystemElectronicsSimulationIntegration
Andrew• Test Stand
Design
• Test Stand Fabrication
• Testing
• Data Analysis
ComponentsAir Muscle Artificial Limb
Test Stand
Solenoid Vacuum Pump
Relays
Air TankStrain Gauge
Elbow joint moved by pneumatic actuators
Holds arm and sensors in place
Controls airflow Sucks air out of muscles
Provide power to and control solenoid
2 count: one holds pressurized air, one is vacuumed
Produces voltage change with displacement
Pressure Gauge w/ Flow Restrictor
Measures and/or slows airflow
Math Model
t
t
e
t
e
0muscle
0muscle
TankTank0muscle
PP
:Drain
28.PP
:Hold
PPPP
:Fill
2
muscle2muscle
2
sin
1sin2P1cos3
4
Pkk tDt
DF
Calculating Air Pressure
Apply Calculation of Force Out of McKibben Air Muscles*
*”Measurement and Modeling of McKibben Pneumatic Artificial Muscles” by Ching-Ping Chou and Blake Hannaford
1) LabView first calculates what air pressure should be in the air muscle given the amount of time that has passed.
2) LabView calculates the force the air muscles should be exerting based on the pressure in the air muscle given a few characteristics of the air muscle.
Components
Air muscles – contract the way they should
Relays and Solenoid – Power works Vacuum Pump – Failed to power up;
worked after rewiring
Pressure Tests
Muscles filled with air at different increments (0.05, 0.125, 0.25 seconds)
Data fitted to function
Fitted Curve
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
0.00 0.50 1.00 1.50 2.00 2.50 3.00
Pres
sure
(psi
)
Time (sec)
Case Fill
Fitted Theory
Elastic Cord/Strain Gauge
Elastic Cord
k≈0.212 lbs/in
Strain Gauge
Constant≈2347 lbs/Volt
6 strings, different sizes Weights 50g-2kg added Displacement measured Linear Regression to find k
Cord tied onto gauge Cord displaced set amounts,
voltage measured LRA to find Constant
543210
1.0
0.8
0.6
0.4
0.2
0.0
Weight (lbs)
% D
efo
rmation
Scatterplot of % Deformation vs Weight (lbs)
2.52.01.51.00.5
0.12150
0.12125
0.12100
0.12075
0.12050
Force
Voltage
Scatterplot of Voltage vs Force
Communication is Key!!!
Mechatronics Toolkit is a linking tool between LabVIEW and COSMOS Motion
Each program receives, translates, and passes data to the next program
Lessons Learned
•Using a single 3-position, 5-way solenoid is cheaper than four 2-way, 2-position solenoids, and takes half of the relays.
•Find local suppliers:•Roessel has many pneumatic parts on hand.•Cross Bros has sprockets and chain on hand.
•Don’t rely on non-team members for mission critical parts.
•Start programming earlier.