A Tiny Haptic Knob Based on Magnetorheological Fluids

In this paper, we propose a tiny haptic knob that creates torque feedback in consumer electronic devices. To develop the proposed haptic knob, we use a magnetorheological (MR) fluid. When an input current is applied to a solenoid coil, a magnetic field causes a change in the MR fluid's viscosity. This change allows the proposed haptic knob to generate a resistive torque. We optimize the structure of the haptic knob, in which two operating modes of MR fluids contribute to the actuation simultaneously. We conduct magnetic path simulation and resistive torque simulation using the finite element method and perform experiments to measure the resistive torque and its torque rate according to the rotational speed and applied current. The results show that the proposed haptic knob generates sufficient torque feedback to stimulate users and creates a variety of haptic sensations.