Numerical Analysis of Energy-Efficient Walking Gait with Flexed Knee for a Four-DOF Planar Biped Model

In this paper we solve the energy-efficient periodic gaits for a biped mechanism walking in the sagittal plane. The biped locomotion mechanism that has thighs, shanks and small feet is modeled as a four-degree-of-freedom (DOF) link system composed of a two-DOF stance leg and a two-DOF swing leg that are connected directly at the hip joint. Using the optimal trajectory planning method based on function approximation, we obtained minimum square input torque trajectories of cyclic walking gaits with flexed knee stance leg for both full-actuated and under-actuated models that are similar to those of the human walking. Also, the validity of this gait generating method is confirmed by forward dynamic simulation.