Optimal Gait Planning for a Biped Robot by employing Active Toe Joints and Heels

In this article, the significance of utilizing active toe joints in biped robots feet is examined. The main goal of this research is to employ active toe joints and heels to improve gait performance from two points of view: actuating torques of knee joints and total consumed energy. Considering the effectiveness of toes and heels in walking, a new walking pattern is fully addressed and compared with another walking pattern which does not exploit toes and heels. In order to develop a verified dynamics model for considered humanoid robot with 22 DoFs, two analytical methods i.e. Lagrange and Kane are adopted and the obtained results are compared. To reduce calculation burden, an iterative method for dynamics model development is proposed, based on Kane approach. Furthermore, to verify the obtained ground reaction forces and moments, ZMP is computed and compared using two methods. In the procedure of gait planning, first the pelvis trajectory is planned. Then, the feet trajectory planning process is done. After designing trajectory in task space, all joint trajectories except the trajectories of toes are obtained, using closed-form inverse kinematics solution. Toe joints trajectories are planned separately, considering the sole trajectories. Consequently, the significant parameters in gait planning are considered as design variables in optimization procedure in order to reduce the maximum torque of knees and total consumed energy as cost functions. Finally, it is demonstrated that which walking pattern is highly appropriate for walking with large step length on flat terrain, under joint torque and velocity limitations.