Simultaneous Force, Torque, Position, and Orientation Control of a Robot Manipulator on a Constrained Surface Incorporating Force Sensor Feedback

This paper proposes a new control scheme which simultaneously regulates and tracks the force, torque, position, and orientation of the end effector of a robot manipulator along a constrained surface. A general model for constrained surfaces is derived. A general control structure using information from both the joint encoders and a force/torque sensor attached to the wrist is presented. From these devices, the current position and orientation of the end effector along with the applied forces and torques can be calculated. Models of both the constraint surface and the compliance of the end effector are included into the control algorithm. This leads to a more robust control strategy than previously developed. Simulation studies show that the steady state error of the system in the regulator mode goes to zero, even with significant errors in the constraint location and orientation. In the tracking mode, the steady state error goes to zero if there is only an error in the offset of the constraint. If there is an orientation error in the constraint while the system is in the tracking mode, then there will be a constant error in the force component. In both modes, the controller will exhibit zero error if the constraint is exactly modeled.