Control formulation of a highly complex wire-driven mechanism in a surgical robot based on an extensive assessment of surgical tool-tip position/orientation using optical tracking system

This paper presents a performance assessment of a highly complex wire-driven mechanical system in a surgical robot, MU-LapaRobot. The MU-LapaRobot is a collaborative surgical robot, developed for ongoing robotic research for laparoscopic surgical application. The MU-LapaRobot consists of 1-DOF passive joint for vertical motion, 2-DOF passive boom for planar motions and 4-DOF active surgical tool-holder using parallel mechanism to create a remote center of motion (RCM). The actuating system is located at the robot base, to avoid a motor weight problem for the system, which requires a wire-driven transmitting system to relay the actuating power to the active joints. The developed wire-driven transmitting system is a very complex mechanical system, which generates uncertain behaviors in surgical tool-tip positioning control. This study is to extensively assess the control behaviors of the MU-LapaRobot system for the design of its control formulation to compensate the control uncertainty. The study begins with an investigation under the direct control procedures using a motor controlling system, Maxon EPOS 24/5 positioning controller. The study employs an optical tracking system, NDI Polaris Vicra, to track and collect positions and orientations of the surgical tool-tip in assessment procedure. After gathering the results from the extensive assessment, a control formulation, to compensate for the control uncertainty, has been developed. The results of implementation on the new control formulation have shown decent responses on surgical tool-tip positioning control in MULapaRobot.