In robotic surgery, the load exerted on the insertion port in the patient’s abdominal wall due to misalignment of the robot’s remote center of motion and the insertion port or external forces acting on the tip of the forceps during surgery, can not only stress the patient’s body but also increase the friction between the robotic forceps and the trocar, and adversely affect fine surgical manipulations or the accuracy of force estimation. To reduce such loads on the insertion port in robotic surgery, this study proposes a control method for a surgical assist robotic arm with semi-active joints. The control method was implemented on a six-degree-of-freedom pneumatically driven vertical multi-joint robotic arm with a two-axis gimbal joint (two semi-active joints) that only executes torque control, which was previously developed by the authors, and verified through an experiment. The load on the insertion port is reduced by applying torque control on the semi-active joints to compensate for the external forces on the forceps. We constructed a control system that includes a disturbance compensator and conducted a velocity-control experiment by subjecting the forceps constrained by the insertion port to an external force. The results showed that when the torque was compensated for by the semi-active joints, the load on the insertion port was reduced by 65% and 52% when the external force on the tip of the forceps was 0 N and 3 N, respectively.
External force estimation for robotic manipulator base on particle swarm optimization
