Active compliance control for a hydraulically-actuated articulated robotic leg

This paper focus on the modelling and control of a hydraulically-actuated biologically-inspired articulated robotic leg. The leg has two hydraulically-actuated degrees of freedom (DoF), the hip and knee joints, and a passive spring DoF, the ankle joint. After a brief description of the prototype leg, the paper developed a nonlinear model of the leg, including its kinematics and dynamics. Subsequently, an actively compliant control architecture based on outer virtual compliant leg model and inner torque controller was designed to achieve a spring-damper like touchdown dynamics behavior. Lastly, both a Pushdown experiment and a Dropdown experiment were carried to verify the designed controller. The result confirmed that a hydraulically-actuated robot articulated leg can successfully emulate virtual passive components through proper mechanical design and actively compliant control under dynamic situations.