Abstract: With the increase of large-scale, diversified, and high-precision on-orbit construction tasks, new demands on the capabilities are put forward for extra-vehicular space manipulators. Although the traditional SSRMS-type space manipulator is widely used in on-orbit services, it has task-specific structural characteristics that limit the ability of an individual manipulator to perform different types of tasks. Thus, the traditional manipulator has difficulty meeting the demands of the complicated development of future on-orbit tasks. To this end, a novel SSRMS-type reconfigurable space manipulator with two passive telescopic links is proposed, and its kinematic singularities are analyzed in depth. First, the advantages of the work performance for the new manipulator are summarized by introducing its structural characteristics and reconfigurable principle. They proved that the new manipulator has the potential to play a vital role in future on-orbit tasks. Then the differential kinematics equations of the new manipulator in free space operation and reconstruction operation are established, respectively, and the Jacobian matrix that contains kinematics singular conditions is obtained by analyzing the differential inverse kinematics equations. Next, a simple and reliable kinematic singularity analysis method is proposed, and all kinematic singularity conditions of the new manipulator are obtained by analyzing the Jacobian matrix. Finally, the new manipulator is taken as an example, verification experiments are carried out. The results show that the singularity conditions can not only correctly determine the singularity configuration but also serve as an a priori condition to guide the singularity avoidance motion control when the manipulator performs the operation task, providing a powerful guarantee for the reliable implementation of the operation task.

Key words: space manipulator, reconfigurable manipulator, passive telescopic link, differential kinematics, singularity analysis