[ODE] redundant constrain problems?

[Graham Fyffe]

On 5/3/05, Martin C. Martin <martin at metahuman.org> wrote:
> 
> Graham Fyffe wrote:
>  > Hi, Martin.  My problem actually arises with a kinematic loop of
>  > joints in a suspension rig.  I've got this:
>  >
>  > car chassis - ball joint (horizontal) - suspension arm - ball joint -
>  > spindel - hinge joint (vertical) - strut bottom - slider joint - strut
>  > top - hinge joint (horizontal) - car chassis
> 
> I couldn't quite picture your setup from your description.  Is it like
> one of these diagrams?
> 
> http://www.chris-longhurst.com/carbibles/index.html?menu.html&suspension_bible.html


Yes, it's exactly a MacPherson strut.

[...]
> Anyway, if that's not the problem, it could be ODE trying to overcome
> small errors.  Although the solver is supposed to be good at dealing
> with those.  Have you tried using different solvers?  Does the choice of
> solver make any difference?

Yes, quickstep and stepfast are both entirely unable to solve the
kinematic loop :(  The whole thing just flops around like a wet
noodle.
 
- Graham