Bionic control scheme based on muscle-tendon unit for electrohydraulic cylinder

Bionics researchers identify muscle-tendon unit to be effective in producing human-like walking, but seldom real actuators have same property like muscle-tendon unit. Here, a muscle-tendon control scheme for electrohydraulic cylinder is proposed. To achieve this goal, we develop a model of electrohydraulic cylinder to clarify the relationship between the input current and output force. Additionally, a controller based on muscle-tendon unit model is applied to realize compliant control. The results of muscle-tendon unit control scheme and conventional force-position control scheme are compared. By applying the proposed one, we find that the electrohydraulic cylinder generates compliant behavior and self-adapts to load disturbances, without scarifying its fast response property and stiffness. Besides, various compliances can be accomplished by simply changing maximum muscle-tendon unit force. The results suggest that hydraulic actuators with this bionic control scheme can meet the demand of robot applications, especially for legged robots and manipulators.