A Review on Planning and Control of Space Manipulator for On-orbit Capture

With the rapid development of space technology, space manipulators have progressively found applications in the field of on-orbit services, such as debris removal, malfunction satellite capturing and repairing. During on-orbit services, the space manipulators are required to track a pre-planned trajectory and then execute the capture operation. The dynamic properties of space manipulators, such as dynamic singularity and the coupling between the base and manipulator, make their path planning methods different from those of fixed base manipulators. To guarantee the successful implementation of the capture operation, factors such as base disturbance minimization, obstacle avoidance, velocity constraints and other criteria should also be considered during path planning. Afterwards, an appropriate tracking control strategy should be developed to drive the end-effector to the capture point. The relative motion between space manipulators and captured targets limits the time available for performing the capture operation, so the space manipulators should reach the capture point promptly. Working in the complex space environment, space manipulators inevitably encounter unknown external disturbances and parametric uncertainties, which can affect the control accuracy. Thus, the proposed control strategy should not only ensure the stability of the system, but also maintain high precision, fast convergence and strong robustness. Before launching into space, the space manipulator systems require thorough verifications on the ground to test their performance. The design of the ground verifications should accurately reflect real space motion, with a key focus on simulating the microgravity environment in the space. To address these technical challenges, this paper reviews recently progress in path planning, tracking control and ground verification technologies for space manipulators in on-orbit capture. Subsequently, existing drawbacks and future developments of space manipulators are discussed.