Leg space observer on biarticular actuated two-link manipulator for realizing spring loaded inverted pendulum model

This paper proposes kinematics and a control algorithm to control a two-link manipulator to simulate a spring loaded inverted pendulum (SLIP). End-effector kinematics is derived in the reference frame that is defined along the axis that connects the first joint and the end-effector. The derivation of this kinematics reveals that a biarticular actuator is suitable for this kinematics. Based on this kinematics, a disturbance observer is designed in the same reference frame. This disturbance observer removes the unnecessary inertia coupling without calculation of Jacobian matrix.