Human-guided desired RCM constraint manipulation with applications in robotic surgery: A torque level control approach

In robot assisted minimally invasive surgery long and slender tools are used, which are inserted inside the patient's body through tiny incisions in the patient's skin via a trocar. If a general purpose manipulator is used, the trocar is not rigidly attached to the environment. An active approach is therefore needed to constrain its motion so that the wall of the incision is not stressed. In hands-on manipulation, a human exerts forces on the robot's end-effector in order to change the position of the tool tip. In these hands-on operations, it is difficult for a human to know which generalized forces, exerted at the manipulators end-effector, would not affect the constraint while achieving the desired tip positioning. We address this problem by proposing a control input at the torque level which ensures the satisfaction of the desired constraint, under the exertion of a human generalized guiding force, while achieving a desired tool tip position. Simulation results with a KUKA LWR4+ robot demonstrate and compare the effectiveness and performance of the proposed control scheme for the case of a constraint compatible desired end-effector pose.