Development of a new torque feedback device featuring compact MR brake for haptic systems

In this paper, a torque feedback device (TFD) based on a magneto-rheological brake (MRB) is developed for haptic systems. The MRB-based TFD incorporates an innovative rectangular tooth-shaped (TS) magneto-rheological fluid channel. Key structural elements, such as the number of teeth, exciting coils, and tooth geometry, are optimized to enhance torque performance while minimizing energy consumption. Initially, four configurations of rectangular TSMRB-based TFDs are proposed, and the modeling and structural optimization are subsequently implemented, followed by a decision support for a specific haptic application case study. The configuration of double side coils and two teeth is demonstrated to be the most suitable in terms of dynamic range, power consumption and manufacturing feasibility compared to previous studies. A prototype of the optimal TSMRB-based TFD is then fabricated, and a closed-loop controller is designed and experiments are conducted to evaluate its feedback performance. The experimental responses of the TFD prototype show good agreement with a steady-state torque error of approximately 3.7%. The tracking control results for various input signals demonstrate effective performance at low frequencies, while reduced controllability at higher frequencies reflects the inherent hysteresis behavior of the MRF.