Parallelogram Robot Dynamically enabled

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Al.mirante
Posts: 1
Joined: 10 Feb 2020, 21:24

Parallelogram Robot Dynamically enabled

Post by Al.mirante » 11 Feb 2020, 10:09

Hello everybody,

I'm looking for a guide to understand how to build a parallelogram robot like the uarm that is present in the model folder. Currently I have a model of a parallelogram structure that works without the dynamic and with passive joints set to dependent mode. If I enable the dynamic with this configuration, the parallelogram structure fall down. Does anyone know how to deal with this robot?

Thank you.

coppelia
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Posts: 7691
Joined: 14 Dec 2012, 00:25

Re: Parallelogram Robot Dynamically enabled

Post by coppelia » 11 Feb 2020, 14:59

Hello,

that kind of robots is tricky, when dynamically simulated. You have at least two possibilities: you can create the robot as a serial manipulator, and close loops where they need to be closed, using a loop closure constraint. This does not always give satisfying results.
Another option (and this is how it was done in the Uarm example) is to build the robot as a serial manipulator, and close loops by using additional position control-enabled joints, that would apply target angles depending on the angular value of another joint. This is best done via a joint control callback, where you can adjust the joint's target angle in each dynamic simulation step. In the uarm robot model, this happens with joints uarm_auxMotor1 and uarm_auxMotor2

Cheers

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