Magnetic induction control with embedded sensor for elimination of hysteresis in magnetorheological brakes

Abstract

This research explored a novel control scheme for magnetorheological brakes to eliminate hysteresis. A Hall-effect sensor is embedded in the flux path to measure the magnetic flux across the magnetorheological fluid. A proportional–integral–derivative controller then controls the magnetic induction directly. To the best of our knowledge, this is the first such design incorporated into a magnetorheological brake. Even though magnetorheological brakes have very desirable characteristics, such as high torque-to-volume ratio and inherent stability, they have a major drawback since they exhibit hysteresis behavior. The hysteresis creates control challenges and significant residual off-state torque, which prevents use of high gear ratios with magnetorheological brakes. The proposed approach is easy to implement and very inexpensive compared to hysteresis modeling techniques or using force/torque sensors. A prototype brake has been experimentally evaluated using three different closed-loop compensation schemes: (a) the Preisach hysteresis model, (b) torque sensor, and (c) the proposed new approach. Results showed that the proposed control scheme could eliminate the hysteretic behavior and reduce the off-state torque in the magnetorheological brake to negligible levels.