Abstract: In view of the mechanical vibration of the manipulator joint servo system due to the existence of

flexible links such as harmonic reducer and toothed belt，a mathematical model considering the change of stiffness

coefficient and large reduction ratio was established，the mechanism of mechanical resonance was analyzed，and a dynamic torque feedback control strategy was proposed. The dynamic torque was observed in real time by a

disturbance observer to form a dynamic torque closed loop. In order to further suppress the vibration phenomenon

and enhance the robustness and disturbance rejection ability of the system，the speed variable gain PI control

method adjusted in real time with dynamic torque was studied. Simulation results show that the speed variable gain

PI control strategy with dynamic torque feedback can suppress mechanical vibration well，and has strong antidisturbance ability and dynamic response performance.

     Key words: mechanical resonance；variable gain PI control；dynamic torque feedback；disturbance observer