Fastest walk control of quadruped robots for trot gait by using torque redundancy of leg joints

A way of deriving the fastest walk pattern of quadruped robots for trot gait is developed and installed into a practical robot system. Two support legs and the body are modeled as a five-link manipulator and each swinging leg is modeled as a two link manipulator respectively. As a first step, the fastest walk pattern of support legs is designed under the constraints of torque limits of leg joints and friction forces at the support leg tips. Then, the time optimal motion pattern of each swing leg is designed under the boundary conditions given by the obtained walk pattern of the support legs. The fastest walk patterns of support legs and swinging legs are designed respectively. Therefore, if the time optimal motion pattern of swinging legs doesn't satisfy the boundary conditions given by support legs, the same procedures are iterated by modifying a velocity parameter of the support legs until the boundary conditions are satisfied. SONY ERS-7 is used as a quadruped walking robot and some fundamental experiments are done to verify the effectiveness of the developed control algorithm. From the results, it is revealed that the proposed method is particularly effective on the ground with large friction coefficients.