CoppeliaSim forums

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.

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