Grasping issues

[tompalmer]

I'm trying to use Bullet for grasping simulation. I've built fingers with btGeneric6DofConstraint. Some of my settings are as follows:

Code: Select all

constraint->setAngularLowerLimit(btVector3(pi(-0.4),pi(-0.01),pi(-0.1)));
constraint->setAngularUpperLimit(btVector3(pi(0.05),pi(0.01),pi(0.1)));
constraint->getRotationalLimitMotor(0)->m_enableMotor = true;
constraint->getRotationalLimitMotor(0)->m_targetVelocity = -1;
constraint->getRotationalLimitMotor(0)->m_maxMotorForce = 10;

The issue I see is with bouncing/instability. The fingers move in towards the joint limits, but then they fall down or bounce back and have a hard time stabilizing. No contact with other objects yet. Any recommendations about how to just make the fingers move towards the limit then stop?

A related question is about actual grasping itself. I'll want the fingers to close in on an object then stop at the object surface while still exerting some amount of force at the joints. It seems like target velocity isn't an ideal formulation for this. But that's the only option I see here. I haven't read all the code. I presume that if the target velocity is far from the current, that it will exert the max force? And even still, I'll want to avoid the bounce concern mentioned above.

Thanks for any help.