Design of muscle reflex control for human upright standing push-recovery based on series elastic actuator

Ankle joint muscle reflex control plays an important role in the human bipedal posture. With the neuromuscular control mechanism and muscle-tendon biomechanical dynamic properties, our joints exhibit excellent performance in external environment physical interaction. Researching and understanding the mechanism of muscle reflex not only helps to reveal human movement control rules, but also provides a useful tool for robotic system design. In this paper, an ankle joint muscle reflex control strategy for human upright standing push-recovery is proposed. In order to focus attention on muscle reflexes and exclude other control mechanisms from the central nervous system (CNS) as much as possible, only ankle joint strategy without foot tilting is evoked by a limited external disturbance. A proportional derivative-like (PD-like) muscle reflex control algorithm is presented to understand the action mechanism for human upright standing push-recovery. A series elastic actuator (SEA) based mechanical ankle joint is designed as a platform for testing activities. The experimental results show that the proposed reflex control method can help subjects maintain balance, without stepping, while receiving external disturbances. With the unique control mechanism, the ankle joint behaves like a spring-damping system. And, under such a simple and effective control strategy, it is practical to realize human upright standing push-recovery.