Control of a Space Manipulator Capturing a Rotating Object in the Three-dimensional Space

For space robots accomplishing the overwhelming majority of on-orbit servicing(OOS) missions, capture of a target object is the primary task. Capture of a rotating object in orbit is an especially important and challenging task for OOS such as orbital debris removal. This paper studies the control strategy for capturing a fast rotating object by a space manipulator from a floating spacecraft in the three-dimensional space. First, in order to simulate the real contact condition as much as possible, a contact dynamics model considering the effect of the contact geometry of the capture interfaces is built. Second, the control strategy is proposed by a combination of a resolved motion rate control method and hybrid impedance control technique. The stability is proved by Lyapunov theorem. Finally, a simulation example of a 7-joint manipulator capturing a rotating target object in the unrestricted three-dimensional space is conducted to verify the feasibility and efficiency of the control strategy. In the effect of the control law, relative velocity at the contact spots is reduced, and thus the target object at an initial rotation speed of 12 deg/s (2 rpm) is captured successfully.