Time optimal control for quadruped robots by using torque redundancy

A time optimal control algorithm for quadruped robots is developed and its effectiveness is verified by experiments and simulations. The derivation of the optimal solution consists of two steps that are the speeding up of supporting legs and that of swinging legs. The way of the speeding up of swinging legs is very similar to that of a two link manipulator developed by Bobrow. In this paper, first, a method of using torque redundancy of the robot is proposed for speeding up of supporting legs with the constraints due to ZMP, the power limits of joint actuators and the limits of available friction forces. Then, an algorithm for obtaining the fastest walking pattern in a trot gait period is developed by combining the result of the supporting legs and that of the swinging legs. The obtained walking pattern is installed in a quadruped robot SONY ERS-7 and its effectiveness is verified by experiments.