Point-to-point planning for free-floating space manipulator with zero-disturbance spacecraft attitude

The free-floating space manipulator (FFSM) system is the one in which the spacecraft´s attitude is not actively controlled during manipulator activity to conserve fuel of the spacecraft. In this case, the spacecraft will move freely in response to the disturbances caused by the manipulator motions. From the viewpoint of the application, the spacecraft attitude change of the FFSM system is not desirable. A point-to-point planning approach of the FFSM is presented to ensure that the manipulator end-effector reaches the desired point and the spacecraft attitude is zero-disturbance simultaneously, only by manipulator motion planning. With the introduction of the correlative coefficient, whether the singularities of the current path points happen could be judged. If it doesn´t happen, the zero-disturbance vector synthesis algorithm in Cartesian space is utilized to find the next point; otherwise, the comparison planning algorithm in joint space is employed to find the next point. Thus, the approach satisfies the requirement of the former algorithm to the non-singularity of the path point, and to some degree overcomes the limitation of only using the latter algorithm. Hence, the path planning approach could be realized in entire workspace of the FFSM with zero-disturbance spacecraft attitude. The effectiveness and feasibility of the proposed approach is verified by simulation results.