Chain of joints with PID position control

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bessemermine
Posts: 16
Joined: 13 Mar 2013, 23:05

Chain of joints with PID position control

Post by bessemermine »

I'm trying to build up an approximation to a springy structure using a few segments with joints, with the joints in position control mode to mimick the internal spring/damper effect.

Here's the test scene that I'm putting together to test the idea, but the behavior is not right:
http://tinyurl.com/ca4omuy

The graphs show that the angles are diverging from the desired setpoints, but the torque is not responding accordingly. The "bounding ball" icon shows next to all the shapes and joints, so it seems as though everything is active, but I'd expect the behavior to be for the structure to stabilize to a constant height, and probably undergo a hopping oscillation.

If this is just some physics problem I'm overlooking, then that'll be embarrassing. But if it's a settings problem, any input would be appreciated.

coppelia
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Posts: 10339
Joined: 14 Dec 2012, 00:25

Re: Chain of joints with PID position control

Post by coppelia »

Hello,

Did you play with the example model in models/examples? Also, make sure to read this topic.

When you have a chain, the problem is always more complex because all elements influence each other. Before going any further, you could try to write your own low-level joint controller, and implement the spring yourself. There is a new feature for that from V-REP 3.0.2: callback scripts

Cheers

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