Joint/motor dynamics

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rab
Posts: 3
Joined: 19 Feb 2013, 16:01

Joint/motor dynamics

Post by rab »

Hello,

I have read some of the discussions on this forum but I dont seem to get a clear idea if what I am trying to do is possible.
What I am trying to do is to change the behaviour/dynamics of the joints/motors using torque control, basically I want to increase the damping of the joint. There are some constants that can be manipulated under "Engine specific properties", the bullet and ODE but none of them seem to have the affect Im looking for.

Is it possible to increase the damping of joint using the torque control and not the position control?

coppelia
Site Admin
Posts: 7936
Joined: 14 Dec 2012, 00:25

Re: Joint/motor dynamics

Post by coppelia »

Hello,

Yes, this is possible. You have several possibilities:

1. The easiest and best would be to wait for the next release (V-REP V3.0.2) scheduled for mid-March 2013. There, you will have a mechanism that allows you to write a custom control loop for any joints, directly as a script.

2. You can modifiy the source code for your needs. This will however require you to recompile the dynamics plugin, and additionally, you will lose compatibility with other installations (which is not the case with method 1)

3. You can write a custom joint control loop in a child script. The only problem is that the child script will run once at each simulation pass, which is 10 times less than the physics engine steps (i.e. by default, the physics engine runs 10 steps each time the simulation advancs by one step). You could reduce the simulation time step to 5ms, in order to have a 1-to-1 correspondance. But this is not elegant.

4. With the built-in PID controller, you can achieve many tasks, including simulation of a spring coupled with an appropriate damper. Refer to the demo model "models/examples/spring-damper.ttm"

Cheers

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