Design and analysis of a regenerative magnetorheological actuator for gait assistance in knee joint

In this paper, we propose and analyze a Regenerative Magnetorheological Actuator (RMRA) for gait assistance in knee joint. The actuator has motor and magnetorheological (MR) brake parts working in parallel, and can harvest energy through regenerative braking. This novel design provides multiple functions with good energy efficiency. The design of the RMRA is first introduced, and its multiple functions are modeled. Different working modes of the RMRA are analyzed for mimicking knee joint functions within gait cycle. To achieve an effective and energy efficient braking function, cooperation between regenerative braking and MR braking is investigated. The energy harvesting (EH) circuit equivalent load is further optimized for maximal energy harvested within a gait cycle. Then impedance based braking control of the RMRA for gait assistance is proposed. Preliminary simulation shows that the developed RMRA with proposed control strategy can provide desired torque assistance during normal gait.