Impedance Control of Robotic Forceps for Safe Robotic Surgery

This paper proposes a switching control system of robotic forceps to enhance the safety of robotic surgery. When the robotic forceps contacted with environment at the outside of the laparoscopic field of view, surgeons can easily damage an internal organs of patient. Therefore, control mode of the surgical robot is automatically switched based on the existence of the robotic forceps in the laparoscopic field of view. The detection of the robotic forceps in the laparoscopic image is performed through image processing on the basis of threshold criteria. Then, when the robotic forceps was recognized as outside of the laparoscopic field of view, a position tracking control combined with an impedance control is conducted. In this case, if the robotic forceps contacted with an internal organ of patient, the control system loosens contact force between the robotic forceps and the internal organ, so that the robotic forceps deflects from the internal organ. Thus, the risk of the surgical robot unexpectedly damaging the internal organ is expected to be reduced. On the other hand, when the robotic forceps was recognized as inside of the laparoscopic field of view, just a position tracking control is conducted. In this case, surgeon can obtain a required contact force for performing surgical procedure between the robotic forceps and the internal organ. In order to verify an effectiveness of the proposed switching control system, the control system was applied to a robotic surgical system developed in our previous study, and evaluation experiments were carried out.