Compact forceps manipulator for laparoscopic surgery

Forceps manipulating robots have been developed for assisting surgeons to realize high-quality and precise operation in laparoscopic surgery. Currently several commercially available systems greatly contributed to operations. Still their large size causes problems in the operating theater, thus they need to be miniaturized. We developed a new compact forceps manipulator. It consists of two parts; friction wheel mechanism which rotates and translates the forceps (62×52×150[mm³], 0.6[kg]), and gimbals mechanism which drives the forceps around the incision hole on the abdomen to determine the direction of forceps (135×165×300[mm³], 1.1[kg]). Thus, the four DOF motion of forceps in laparoscopic surgery was realized. Ultrasonic motor was adopted for actuating friction wheel mechanism because of its small size, high torque and cleanliness. We controlled the manipulator in semi-closed loop using rotary encoders. Mechanical evaluation results showed that feedback loop control and compensation of control command improved the positioning accuracy. Positioning accuracy of the gimbals mechanism was less than 0.6 [deg], and that of friction wheel mechanism was less than 0.2 [mm] in translation and 1 [deg] in rotation. In vitro experiment simulating usage in the clinical environment revealed that this manipulator realized stable motion even if the liquid materials such as blood attached onto the forceps. The new manipulator was promising and useful in laparoscopic surgery.