On cartesian motions with singularities avoidance for free-floating space robots

Free-floating space manipulator systems have spacecraft actuators turned off and exhibit nonholonomic behavior due to angular momentum conservation. Such systems are subject to path dependent Dynamic Singularities (DS) that complicate their path planning. Due to the existence of DS its workspace is restricted. The Cartesian space path planning of free-floating space robots is studied and a novel path planning technique allowing the end-effector to follow a desired path avoiding any DS is proposed. Since the path is predefined, the method yields the appropriate initial system configurations that avoid dynamically singular configurations during the motion. Therefore, it allows effective use of the entire robot workspace. The proposed method is applicable to both planar and spatial systems and it is demonstrated using straight-line paths. The application of the method is illustrated by two examples.