Kinematically Indeterminate

Hi,

I’ve been working to drive my model with markers, and I am stuck with
the error, “Position analysis failed because the system is
kinematically indeterminate.” I can get the model to compile fine,
however once I try to set my initial positions, the model is unable to
do so. The model is not overconstrained (based on my Model
Information output), and gimbel lock is not an issue, so I’m stuck
right now. Any suggestions?

Thanks,
Sarah

Hi Sarah,

The compilation process only checks the semantics of the model, so it
can be kinematically indeterminate also when it compiles fine.

The second check, as you know, is to run the ModelInfo operation and
check that the degrees of freedom and constraints add up.

Even when this is the case, the model can be kinematicaly
indeterminate. It can happen for several reasons:

  1. If one part of the model is over constrained and another is under
    constrained, then they can add up to zero and still leave some part of
    the model kinematically indeterminate.

  2. Even if the one part of the model is in balance with respect to
    number of degrees of freedom and constraints, the constraints can fail
    to determine the position uniquely due to the nonlinearity of the
    problem. This can happen if two constraints in some position become
    linearly dependent.

We do not have much time in the support department to devote to
individual problems right before the holidays, but if you zip and
upload the ARep part of your model to the group then we shall take a
look at it as soon as we can. This will probably not be until after
Christmas.

Best regards,
John

— In anyscript@yahoogroups.com, “Sarah R. Sullivan” <sarsulli@e…>
wrote:
>
> Hi,
>
> I’ve been working to drive my model with markers, and I am stuck with
> the error, “Position analysis failed because the system is
> kinematically indeterminate.” I can get the model to compile fine,
> however once I try to set my initial positions, the model is unable to
> do so. The model is not overconstrained (based on my Model
> Information output), and gimbel lock is not an issue, so I’m stuck
> right now. Any suggestions?
>
> Thanks,
> Sarah
>