A novel guidance strategy for autonomously approaching a tumbling target

A novel guidance strategy is developed based on the artificial potential function for a chaser spacecraft to autonomously approach a freely tumbling target in the on-orbit servicing missions, which can generate the desired velocity instruction for the chaser spacecraft. Considering the collision avoidance constraints, the motion of the tumbling target is classified into three cases. The tumbling axis of the target is perpendicular to its docking port axis in Case 1, and the two axes are nonorthogonal in Case 2, and the two axes are in line in Case 3. Different safe boundaries are established for Case 1 and Case 2, and the desired velocity instruction is determined using the novel guidance strategy, respectively. The method for Case 3 is similar to Case 2. A sliding model controller is designed to control the chaser spacecraft to satisfy the desired velocity instruction. Numerical simulations are performed, and the results show that the developed guidance strategy is an effective method to solve the problem of autonomously approaching a tumbling target.