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.