Abstract:  An optimal reaction control method was proposed for the trajectory tracking problem of the end effector of flexible base redundant manipulator systems.In the proposed algorithm，trace tracking is regarded as a high-priority task and the optimization of reaction control is implemented in the null-space of high-priority task.The self-motion of redundant manipulator can alter joint motion without affecting the motion of the end-effector，and can nullify the dominant modal force of vibrating system.Therefore，the vibration of base excited by rigid body motion is reduced greatly when the manipulator tracks specific trajectory.As a result，the stability of systems is improved.The effectiveness of the proposed algorithm is confirmed through numerical simulation with three-link manipulators and seven-DOF space manipulators with flexible base.

Key words: flexible base, redundant manipulator, self-motion utilization, optimal reaction, vibration suppression, trajectory tracking