Force and motion management in legged locomotion

The control of a legged locomotion system over uneven terrain requires a new approach to coordination. The system has a high degree of static indeterminacy and, because of the stiffness of the structural and actuation systems, has stability problems if position-velocity control is used. The problem has many similarities to that of grasping and manipulating an object in a multi-fingered hand. The stability problem is removed by controlling actuator force directly, but the necessary computations can be prohibitive. A solution is presented which is moderate in its computational requirements. It is based on an assumption of zero foot interaction forces in the horizontal plane.