Trajectory Planning of Walking With Different Step Lengths of a Seven-Link Biped Robot

Most of the essential parameters of the human walking can be captured with a seven-link planar biped robot. In this paper, dynamics modeling and trajectory planning of a seven-link planar biped robot walking on a level ground with a ditch or stairs are studied. The hip and foot trajectories are designed in Cartesian space using polynomial interpolation such that to vanish the impact effect of feet with ground. The key parameters of the hip joint trajectory in x-axis direction are obtained using boundaries of biped stable region during the walking to satisfy dynamic stability of robot. Then the highest position of the swing foot ankle joint in x and z-axis direction is optimized with two different fitness functions. Next, a novel method for trajectory planning of walking with different step lengths, uses for online trajectory planning, is proposed. Finally, the effectiveness of the proposed method is verified by simulation and experimental results.