Repulsive torque control of a robot-assisted surgery system using a magnetorheological haptic master

In this work, a repulsive torque control of a robot-assisted surgery system using a 4-degree-of-freedom haptic master which is operated using the properties of magnetorheological fluid is undertaken. The proposed haptic master can generate a repulsive torque along 4-degree-of-freedom motion and provide command signals to the slave robot. This is possible due to controllability of the torque by applying the magnetic field (or current) to magnetorheological fluid domain of the clutch system. For the realization of the master-slave robot-assisted minimally invasive surgery system, an encoder is integrated with the haptic master, and the motion command of the haptic master is realized by the surgical slave robot in the robot-assisted minimally invasive surgery architecture. The haptic master–slave system is then established by incorporating the slave robot with the master device, in which the repulsive torque and position commands are transferred to each other. In order to demonstrate superior performance of the proposed haptic master in terms of torque-tracking controllability between the master and surgical positions, a sliding mode controller is designed and experimentally implemented. It is validated via tracking experiment that superior torque-tracking control performance can be achieved by commanding dynamic motions of the haptic master featured by the inherent characteristics of magnetorheological fluid.