Enhanced Tiny Haptic Dial With T-Shaped Shaft Based on Magnetorheological Fluid

This letter introduces a tiny haptic dial utilizing magnetorheological fluid (MRF) to enhance its resistive torque feedback. Moreover, we design the T-shaped rotary shaft with bumps and embed it into the haptic dial to enhance its haptic performance (resistive torque). This structure enables two operation modes (shear and flow) of MRF that contribute to the actuation simultaneously in the proposed haptic dial. This structure allows the magnetic flux to flow towards the MRF, helping further maximize the resistive torque. We conduct a simulation to confirm that the magnetic flux generated from a solenoid forms a closed-loop magnetic path without magnetic saturation or leakage in the proposed haptic dial. The resistive torque of the proposed haptic dial varied from 8 N·mm to 47 N·mm as the input current changed from 0 to 300 mA, thus indicating that the proposed haptic dial can create a variety of haptic sensations in a tiny size (diameter: 20 mm; height: 20 mm).