Extension of degree-of-freedom of bending motion for Double-Screw-Drive mechanism

Recently, robotic surgical support systems have been clinically used for minimally invasive surgery, and the development of surgical support devices with the application of robot technology is in demand. We have developed a new bending technique with a screw drive mechanism so far, which allows for omnidirectional bending motion by rotating two linkages, each consisting of a right-handed screw, a universal joint and a left-handed screw. The new screw drive mechanism, termed Double-Screw-Drive (DSD) mechanism, was utilized in a multi-DOF robotic forceps manipulator for laparoscopic surgery. In this paper, the DSD mechanism is improved so that the degree of freedom of motion of the tip position is extended. In order to control bending motion of new DSD mechanism, equations which give the amount of rotations of each linkage are derived. In addition, the motion space of the tip position is analyzed using the derived equations.