Modeling and Observation of Rate-Dependent Hysteresis and Creep Phenomena in Magnetorheological Clutch

Magnetorheological clutches (MRCs) are potential to provide jointed robots with the capability of behaving compliantly and safely. However, before achieving those behaviors, the MRCs should be well modeled to capture their complicated nonlinear dynamics including rate-dependent hysteresis and creep phenomena. This article develops a multistate fractional-order MRC model that captures such complicated dynamics. Compared to the classical models, this new model offers better estimation accuracy for the hysteresis and creep phenomena, simultaneously. To further improve the modeling performance, an observer based on the fractional-order model and the supertwisting algorithm is designed to compensate for the model uncertainties. With an implicit-Euler implementation method, the observer can exactly estimate the model uncertainties and then further improve the model prediction. The effectiveness of the proposed fractional-order model and observer is demonstrated with experiments and comparisons with the fractional-order Bouc-Wen model.