On control and planning of a space station robot walker

Abstract

A walking robot which can step from one node of a space station trusswork to the next is described. The five DOF robot consists of two light-weight flexible links, configured like an upside-down V , with a rotary joint at the vertex and a gripper connected by two DOF joints at each free end. The development of the control software is presented. One step of the walking motion is divided into four phases: coarse motion, fine motion, insertion, and extraction. In coarse motion, the robot moves its gripper from one node to the vicinity of another. In fine motion, the robot moves precisely to the top of the hole. The gripper is then inserted along the vertical motion to complete one step, and then the other gripper is extracted to start the next step. The low-level controllers were designed based on a rigid model, with low-pass filtering used to eliminate the high-mode vibration of the flexible links. Acceleration feedback was introduced in the control to improve the system bandwidth. A trajectory for specific walking motion is presented for generating efficient and stable motion