Target Capture via Sliding-Mode Control Incorporating a Reaction Control System

Abstract

The present paper proposes a sliding-mode control method incorporating a strategy to avoid singularities during target capture for a space robot equipped with a manipulator. The position and attitude of the end-effector of the manipulator are controlled by a conventional sliding-mode control employing the transpose of the generalized Jacobian. In the proposed algorithm, the attitude/position of the main body of the space robot is controlled to increase the manipulability when the manipulator approaches a singularity. The direction of the main body translational motion is selected in order to effectively avoid the singularity, and the direction for acceleration of the end-effector is modified taking into account the acceleration of the main body. The gain scheduling technique is also incorporated in order to reduce the control input effort at the beginning of operation as well as to suppress the steady-state error. The effectiveness of the proposed method is verified through numerical simulations for a simple model of a space robot.