[ODE] problems with redundant constraints?

Graham Fyffe gfyffe at gmail.com
Mon Feb 21 12:32:21 MST 2005

Hi!  I want to simulate a wheel that has some torsional "give" to it. 
What I did was connect the drive motor (a Hinge joint) to a "hub"
body, and then connect the hub body to the wheel body using a second
Hinge joint, which has a histop and lostop set to 0.0, and has a
stopCFM and stopERP set up to simulate the torsional springiness. 
Problem is, ODE wigs out completely, flipping the wheel around various
axes when I try to drive the thing on a ground plane.  It's as if the
redundant constraint axis has interfered with the solver.  I am using
WorldStep.  I seem to recall reading about this kind of solver
requiring very careful selection of constraints, so that the degrees
of freedom are known precisely... so what I'm asking is, is there any
way at all to simulate what I'm trying to simulate?  Or, is there any
way to modify ODE to automatically determine the degrees of freedom? 
I've had issues with redundant constraints when buiding suspension
rigs as well.  Thanks!

- Graham Fyffe

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