Experimental investigation of a magnetorheological fluid damper with permanent magnet for haptic finger grasping

Abstract

Haptic devices mimic force or torque responses of physical systems. In active devices, the synthetic responses are usually produced by DC motors, due to their wide range availability and ease of control. On the other hand, simulating rigid collisions require large motors, at the expense of size and weight, or gearboxes at the expense of transparency. Viscosity of magnetorheological fluids (MRF) increases, up to the point of becoming a viscoelastic solid, when they are subjected to a magnetic field. Due to this property, they are used in adjustable dampers, where the damping force is controlled by varying the intensity of the magnetic field via an electromagnet. The use of MRF technology in passive or semi-active haptic devices is an attractive research area, in which, a number of damper designs have been proposed over the last decade. This paper investigates a linear MRF damper for haptic finger grasping applications. The damper incorporates an orifice area which is affected by a position controlled permanent magnet. Proximity of the permanent magnet to the orifice area manipulates the viscosity of the MRF; hence changes the reaction force of the damper.