Minimum energy biped running gait and development of energy regeneration leg

This paper presents a method to generate a trajectory of a biped running motion with minimum energy consumption. It is formulated as an optimal control problem with certain terminal conditions. The problem is to find input joint torques and initial posture that minimize input energy during running motion under the condition that the robot takes completely periodic and symmetric motion, given the step period and the stride. The energy regeneration is considered. Exact and general formulation of the problem based on recursive representation of a robot is proposed. Through the numerical study of a five link planar biped robot, it is found that big peak power and torque is required for the knee joints but its consumption power is negative small and the main work is done by the hip joints. Based on this result, a leg module with elastomer spring joints is introduced for energy regeneration purpose.