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Systems Realization Laboratory
Compact Rescue CrawlerME 6105
04/26/07
Jonathan JobeAndrew Marshall
Chris Weir
Systems Realization Laboratory
Intro to Application Domain
Fluid Power – Pneumatics, part of the NSF funded Fluid Power ERC www.ccefp.org
Robotics – Serial Robot Vehicle, 6 legs: Hexapod Kinematic design for a robot vehicle
• Modeled design was to be optimized for this course
• Model must be interfacable for later use in control design & optimization
Systems Realization Laboratory
Interesting Aspects: FP test bed vehicle – Model must interface with other design groups
• Future models to interface: valves, lines, pneumatic source, controls
Desire to simulate walking on flat ground terrain• Separates a grounded simulation from a “free body structure”
Included Tutorial (Visio diagram)• STL procedure for Geometric Visualization• Mass and Inertial properties procedure for Dynamic Physical Effects
Problems we encountered• Wrapper Difficulties• Maintaining Physical Experiment Requirements
Overall Utility Method
Suggestions / Requests for Software Improvement
Future Work
Systems Realization Laboratory
Physical Design
Design Variables Parameters for Dynamic Model
• Inertia tensors, Center of Mass
• .stl files to represent geometry
• Mass computations from multidensity assemblies
• Uncertain params – damping, fluid pressure, ground reaction forces
Systems Realization Laboratory
Designing in Dymola
Systems Realization Laboratory
Input properties into Dymola
component (i.e. BodyMass)
Create and align coordinate
system in PRO/E with desired orientation in
Dymola
PROE: save as STL File
-Options: ASCII format and coordinate
system
-Rename STL file as a number-In Notepad:
change name at beginning and end
of file to the specified number
Dymola: Add to model using
animation window and change the ‘shapeType’ to
1.dxf, 2.dxf, etc.
3D CAD geometry representative of
component or subassembly
GEOMETRIC PROPERTIES
Generating STL files
INERTIA TENSORMASS
CENTER OF MASS
Export Mass Properties in PRO/E
(All sub-assembly components require
defined densities and coordinate systems)
Edit à Setup à Mass Properties à Generate
Report
STLs ProE PropertiesOrig. created for Stereolithography
(rapid prototyping surface data)
Systems Realization Laboratory
Solving Wrapping Difficulties
Problem: In Dymola Components, if a parameter is used to define a relationship for another parameter within the same code, it will be an unchangeable input quantity in the variable browser of the simulation window.
Hence, it is unchangeable in the wrapper, even though it shows up in the input file.
Solution: Remove the variable dependency. Sometimes this requires creating a custom version of the component.
Systems Realization Laboratory
Preserving Experimental Requirements Problem: Ensuring the experiment is followed every time,
regardless of uncertain variable values or design variable values• Experiment was a step ‘gait’ for a single leg
Proposed Solutions:• Require leg end effector path as experimental definition
Problem: Different sized legs cannot always follow the same gait if it doesn’t fit
• Require leg angles as a function of time Problem: Stroke and other params of the actuators are required to change in
order to preserve range of motion Problem: With a position-based control system, similar actuators could perform
different experiments. Our control required actuator full range of movement.
• Incorporate an experimental failure flag in Dymola, so legitimate runs are used for data in Model Center
Our Solution: leg angles = f(t,…) & custom actuator strokes
Systems Realization Laboratory
Design Variable Dependencies
Adding Length
Systems Realization Laboratory
Utility Function Work Used Excel sheet to update utility surface visual aid as
preferences were elicited • Prevented conflicts & preserved preferential independence
0
0.2
0.4
0.6
0.8
1
1.2
0 0.2 0.4 0.6 0.8 1 1.2
U=f(Ux)
U=f(Uy)
U=f(Uz)
Systems Realization Laboratory
Suggestions for Improvement: Model Center
Unavailability of information during active simulations LHS variable name pass-thrus are a problem when linking or
viewing results Multi-nested model execution
• Uninformed of what is being executed (other than visual block highlighted)
• No progress monitoring – only works sometimes with the ‘bar’
• Optimizer needs to provide feedback Information within its log file or a separate trade study file of runs used to pick
next step direction and line length
Some solution ideas: Email Notifier – for failed runs, completed simulations, etc. Detailed progress monitoring Better handling of complicated executables like Dymosim.exe (see slide notes)
Systems Realization Laboratory
Future Work
Ground model Model validation
• Validating input force vectors at leg end effector for single-leg simulations Data from ground model, or full walking vehicle simulation
• Using Physical Test on CRC Test Bed and list of experiments
• Running model with Phantom input vectors, and validating against physical sensor output vectors
Test tracking module • So that model does not fail (preserve experimental requirements)
Integration of pneumatic control to drive the robot leg• Simulink Controls Module
• Dymola Model in Simulink interfaced with Controls module