We are able to close the RH_P12_RN gripper but not open


We have purchased a RH_P12_RN gripper recently. Are planning on making it the end-effector of a robot, but currently we are simply testing that it works as intended. However, we have run into an issue where we can close the gripper but not open it, and are unsure why this is.

We have attempted to control the gripper with the Dynamixel Wizard, the ROS GUI, and the Dynamixel SDK on Ubuntu 20. We are powering it with a 24V power supply. In position-control mode, we can very precisely close the gripper from the Wizard, but we cannot open it. Additionally, in current-control mode (also from the Wizard) we can more or less open and close the gripper but it only opens a small fraction of the full extent it should be able to. If we increase the maximum current we get an overload error, and the gripper does not open much more anyways. Similarly for the other control interfaces (SDK and ROS GUI), we cannot open the gripper.

We have tried changing many parameters. One thing we have noticed is that if we set Goal Velocity or Goal Current to negative, they immediately flip back to positive when we turn Torque on and try to open the gripper from the Wizard. Unsure if this is expected. Either way, we are unsure what the problem is and would greatly appreciate your help!

Thank you,
Federico Pizarro Bejarano