Torque tracking control of a haptic master featuring controllable magnetorheological fluid

This paper presents newly developed 4-degrees-of-freedom (4-DOF) haptic master associated with controllable magneto-rheological (MR) fluid for robot-assisted minimally invasive surgery (RMIS). In RMIS, the proposed master can be used as a haptic interface in order to restore sense of touch, including recovery of kinesthetic and kinetic information. By utilizing MR fluid, the proposed haptic master can easily generate bi-directional repulsive torque. The proposed master is composed of two actuators: MR bi-directional clutch with planetary gear system and MR clutch with bevel gear system. After explaining the mechanism of MR haptic master, the torque models of MR actuators are mathematically derived on the basis of Bingham model of MR fluid. In order to evaluate the performance of the proposed haptic device, a torque tracking experiment is implemented. It has been shown that the efficacy of the proposed haptic master is high presenting desired torque and actual one in time domain.