Controllable magnetorheological fluid based actuators for 6-degree-of-freedom haptic master applicable to robot-assisted surgery

This work presents controllable magnetorheological (MR) fluid based actuators for the design of a new 6-degree-of-freedom haptic master which can be applicable to robot-assisted surgery. In this work, two different actuators are used. One actuator is controllable MR clutch for the translational motion in three directions of the haptic master body, while the other actuator is controllable MR brake for the rotational motion to reflect the end-effector of the surgical slave robot. The overall mechanism of the proposed haptic master is designed to have a symmetric structure so that the translation and rotation motion becomes independently. This leads to a simple structure with decoupled dynamics between the translation and rotational motions resulting in a fast computation time. In addition, a gravity compensator is designed and integrated with the haptic master to reduce the effect of the inertia. A proportional-integral-derivative controller is then designed and experimentally implemented for the tracking control of the repulsive torque/force of the haptic master. The tracking control result of each axis motion is shown in time domain.