This paper describes a practical method for autonomous capture of a target satellite in space using an on-board manipulator. In retrieving a satellite, a reference trajectory for control of the manipulator is generated with time delay due to the processing time of the target motion estimator and the manipulator controller. Consequently, the control system shows a poor performance and the end-effector sometimes fails to capture the target satellite. To solve this problem, a control system is proposed, which utilizes predictive trajectory based on the target satellite dynamics. The validity and the usefulness of the proposed control method are shown by computer simulations and experiments using a 3D hardware simulator with 9 degrees of freedom.

In autonomous retrieval of a free-flying object, tumbling motion makes it difficult to grapple the objects with an on-board manipulator. This paper presents a new control scheme to capture a tumbling satellite based on a simple dynamical model. The target motion is estimated based on visual information using Kalman filtering technique. The capture planning based on the proposed model becomes simple because the motion of a grapple fixture on a target satellite nearly stops relative to the end-effector of a manipulator. The validity and the usefulness of the proposed method are shown by computer simulations and experiments using a 3-D hardware simulator with 9 degrees of freedom.