Motion control of tumbling spacecraft by repetitive impulse inputs

An angular momentum control of a tumbling spacecraft by applying repetitive impulses from a space robot arm is discussed. By assuming inputs by the arm, the direction, size and timing of the input forces are relatively free to choose. At each control cycle, however, torques parallel to the contact direction cannot be generated. Therefore, the design of controller is not straightforward. To solve this difficulty, the equations of rotational motion are rewritten into simpler forms by applying appropriate coordinates transformation. Then a discrete controller is designed so that the component of the. angular momentum parallel to the contact direction is damped out by choosing the directions of input forces properly. Numerical simulations are given to show that the angular momentum is efficiently damped.