Universal Robots Forum

Torque/force control and trajectory planning data

Hello,

My plan is to create a force-based position controller for the UR5. This implies that the force of the end-effector(in base frame) should be proportional to the position error and the velocity of the end effector: F_ee = k*(x_r-x) + b*ddt(x_r -x). With some constants k and b, x= the postion of the end_effector, and x_r is the desired position.

My first plan was to control the torques of each joint, to acquire the desired end-effector force. However, I noticed that it is not possible to control the torques of the joints separately with the URscript. I also realized that it is neither possible to control the torques via ROS.
Could someone maybe confirm or invalidate that it is impossible to control the torque of each joint separately, directly or indirectly?

Either way, if the latter is indeed impossible, my plan is to use forcemode via the URscript. This already works in the offline simulator of Universal Robits for the UR5. However, this method requires some trajectory planning to avoid singularities. Ofcourse the UR5 has it’s own trajectory planning when one is using move function, to move from point A to B, and I was wondering wheter it is possible to read out this trajectory, to apply it on my force-based controller.

So my question agian:

  1. Could someone maybe confirm or invalidate that it is impossible to control the torque of each joint separately, directly or indirectly?

  2. Is there any possibility to read out the trajectory planning path for two points between two points

Thanks!