[ODE] 6DOF Positioning of Objects
albiston at cynergy.com
Thu Oct 18 13:26:16 MST 2007
You might be able to also add feed-forward control prior to feed-back
(PID controller) processing during abrupt changes. The feed-back
controller will then act to remove any error.
Jon Watte (ODE) wrote:
> Pet peeve: Euler angles don't have Gimball lock; only people thinking
> about 3D rotations suffer Gimball lock :-)
> Anyway, I would recommend manually adding forces and torques to the
> simulated hand to track the movement, instead of trying to do it with
> joints. Just implement a typical PID controller that, based on forward
> extrapolation from the current position and velocity, tries to apply
> force and torque to get the body in the right position for the next
> step, ignoring joints. This is likely to work just fine, as long as
> movements between two frames aren't too abrupt (which they likely won't
> be with a glove). Another approach would be to run an IK solver, and
> apply force and torque based on the output of that, but that's probably
> overkill for your needs.
> The biggest problem, of course, will be that there may be limitations in
> the simulated world, which the hand in the real world won't feel or be
> constrained by, unless you also have a good haptics system.
> / h+
> Rene Weller wrote:
>> and thanks for answering my last stupid question, even if
>> it turned out that it was a bug in my application (when
>> rotating > pi).
>> However, I just have another problem: I want to use a
>> tracker in combination with a cyberglove. Thus, the
>> position and orientation of a virtual hand should be
>> controlled by the tracker, and the movement of the fingers
>> by the glove. When I directly set the position and
>> orientation of the palm from the tracker input, the joints
>> of the fingers that are connected to the palm, go crazy.
>> So I tried to use joints instead of setting the
>> orientation of the palm directly. Therefore I used 3
>> slider joints to control the position and 3 hinge joints
>> for the orientation. But using euler-angles for the hinge
>> joints results in singularities. So it would be better to
>> use quaternions for the orientation.
>> So my question: Is it possible to control the orientation
>> of a ball joint or a motor via quaternions? I couldn`t
>> find something like that in the documentation.
>> Or am I completley wrong and there exists an far easier
>> way for a 6 DOF control for a moving hand?
>> Thanks in advance,
>> ODE mailing list
>> ODE at ode.org
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