Torque-Current Relationship of an MR Brake for Its Open-Loop Control

Active and semiactive actuators have been widely preferred for designing an actuation system for kinesthetic-type haptic devices. Among them, magnetorheological fluid-based brakes (MR brakes) offer potent properties, such as high torque/inertia ratio and less power consumption. However, one of the most critical issues to be resolved is their hysteresis behavior. Various methods for modeling the input/output relationship with hysteresis behavior exist. However, hysteresis compensation approaches, i.e., torque-current hysteresis model, are not widely studied for MR Brakes. Therefore, a hysteresis compensation model approach to account for the nonlinear behavior of MR Brake is proposed, and the model is experimentally validated in this article. The model consists of multiple splines and an algorithm that uses these splines in hysteresis compensation. Being relatively simple and easily implementable are the distinguished features of the presented model since an optimization method is not required. Furthermore, the performance of the proposed method is compared with two methods, torque-to-current mapping and inverse Prandtl-Ishlinskii method. The obtained experimental results are investigated with three performance metrics. Finally, the effect of the operational speed on the performance of the hysteresis compensation model is also discussed.