To study autonomous control of a space robot, the authors developed their Advanced Space Robot Testbed with Redundant Arms (ASTRA). Berthing a satellite moving in space is a difficult and dangerous task when done manually. This paper describes a robot which berthed a mockup satellite moving and rotating in zero gravity. Features of the robot include autonomous approach to a moving target satellite using visual satellite motion estimation, using real-time visual tracking control to track satellite handles with two robot arms, and grasping the satellite handles with minimum mechanical shock using a flexible wrist mechanism and impedance control. The authors ran their satellite berthing experiment on the ASTRA to check its performance.>

A digital shaping filter used to shape the input to digitally controlled flexible plants is derived from an input preshaping technique to reduce residual vibration in the plant output. Results from simulations show that these filters reduce plant residual vibration to zero. In addition, an arbitrary rate digital shaping filter is derived that allows the user to select any sampling rate for the digital system. The examination of these filters in the digital Z domain reveals them to be digital notch filters that are robust to vibration-mode parameter shifts.>