Configurable joint and gravity don't result in smooth movement when going down.

I'm building a machine with a gripper that picks up loads and moves them around. The gripper gives the load some vertical movement range (10cm up and down).

When I move the gripper up, everything works fine. But when it moves down, the load jutters / doesn't move in a smooth way according to gravity.

Is there anything I can do to fix this ?

I've uploaded an example project to illustrate the problem. It includes a scene with a gripper that oscillates and a second scene without a joint. The second scene contains an object that rests on a moving ridgidbody and illustrates that this behavior isn't caused by the joint.

TIA Patrick

Hi PatHightree,

Looked at your problem and you simply need to lower the fixed time step of the time settings to 0.01 ( originaly 0.02) and all is smooth then. You can even go down to 0.005 if the rig becomes more complex as you develop it further.

The issue is the following ( I think, experts, please correct me if I am wrong), the way the pay load interacts with the ground makes the physics engine jumps because the distance travelled at the collision point between two calculation is two great, so decreasing the time step helps solving the physics smoother. I had to deal with such issues myself, and used some particular extrem setting for my excavator simulation:

In there, I have lower the fixed time step AND also increase the physics solver iteration count a lot, so as you develop further and the system start wobbling or else, try increasing the solver iteration as well,

Also I found that on mac the physics is a lot smoother than on windows, but that's of course very dependent on your specs I guess.



I found the answer !

I was positioning the transform of the gripper, but because it is a physics rigidbody, I should have used rigidbody.MovePosition() instead.

Here is the solved scene.