Re: 6DOF Positioning of Objects

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.

-Beau

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.
>
> Cheers,
>
>              / h+
>
>
> Rene Weller wrote:
>   
>> Hello,
>>
>> 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,
>> Rene
>> _______________________________________________
>> ODE mailing list
>> [email protected]
>> http://ode.org/mailman/listinfo/ode
>>
>>
>>   
>>     
> _______________________________________________
> ODE mailing list
> [email protected]
> http://ode.org/mailman/listinfo/ode
>
> __________ NOD32 2599 (20071017) Information __________
>
> This message was checked by NOD32 antivirus system.
> http://www.eset.com
>
>
>
>