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

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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