A 4-DOF haptic master using ER fluid for minimally invasive surgery system application

Abstract

This paper presents a novel 4-degrees-of-freedom (4-DOF) haptic master using a electrorheological (ER) fluid which is applicable to minimally invasive surgery (MIS) systems. By adopting a controllable ER fluid, the master can easily generate 4-DOF repulsive forces with the advantages of a simple mechanism and continuous force control capability. The proposed master consists of two actuators: an ER spherical joint for 3-DOF rotational motion and an ER piston device for 1-DOF translational motion. The generated torque/force models are mathematically derived by analyzing the mechanism geometry and using the Bingham characteristics of an ER Fluid. The haptic master is optimally designed and manufactured based on the mathematical torque/force models. The repulsive torque/force responses are experimentally evaluated and expressed by the first-order and second-order dynamic equations for each motion. A sliding mode controller (SMC), which is known to be robust to uncertainties, is then designed and empirically implemented to achieve the desired torque/force trajectories. It is demonstrated by presenting torque/force tracking results of both rotational and translational motions that the proposed 4-DOF ER haptic master integrated with the SMC can provide an effective haptic control performance for MIS applications.