Using the btGeneric6DofSpringConstraint for motion control

[Verbo]

Hi,

I have been trying to use the class btGeneric6DofSpringConstraint to create a kind of motion controller for our Virtools port of Bullet Physics. The goal is to make a dynamic body mimic the position and orientation of another non-physic object(target) in our simulations (Virtools had the same building blocks called Motion Controller with their package...but it is not free like Bullet, he!he!). Here is what I did:

1) I create a kinematic body with no collision. It is the kinematic representation of the non-physic object that my dynamic body will try to mimic. It is the dynamic object "target".

2) I attach the kinematic target to the dynamic body with a btGeneric6DofSpringConstraint instance, and I initializing them at the same position, in order to have a 0 distance for the equilibrium point.

3) Then, during the simulation, I update the kinematic target position and orientation according to the non-physic object transform.

Unfortunately, for the moment, my results are not satisfying yet. The basic mimic behavior is there, and each time I move the non-physic object, the spring constraint works and bring back the dynamic object at the new position. However, most of the time with a terrible shaking or oscillation that I have a hard time to tune up. If I want the dynamic object to mimic rapidly, then it augments the shaking, then I have to boost the spring damping, but then it slows down the dynamic object, etc, etc. I tested it in a kind of Shuffle Puck Virtools demo and even got some tunneling effects. Yes, even if the shuffle pad target was only moving on a horizontal plane, the physicalized shuffle pad was always shaking like crazy during rapid movement and was sometime flipping and ending up UNDER the physicalized ground.

Am I using the proper implementation here or should I use a different approach? The principal goal of this feature was to allow us to control some physicalized object without turning them into kinematic objects.

Any help will be more than appreciated(I would pay the beer, but I guess we are all a bit too far...).

Thx.

Verbo

[Verbo]

Hi guys,

Haven`t any answer yet about that topic. Does anyone knows a hint that could help me acheive what I am looking for?

Thanks

Verbo