Abstract: A simple position control strategy in stages is presented for the underactuated planar manipulator with passive joints and flexible links. The assumed mode dynamic model is established of a 2R underactuated manipulator with a second flexible link and a second passive joint. The dynamic coupling characteristics and the controllability of this system are analyzed. The position control strategy of this manipulator is investigated in stages based on the switch of the brake at the passive joint. And the corresponding algorithms of both the active and passive joints are designed by using the PID method. Finally, on the basis of a self-designed experimental setup of an underactuated planar manipulator, the position control of this 2R underactuated planar flexible manipulator is experimentally completed. The simulative and experimental results illustrate that the active and passive joints can track the targets perfectly in respective stage and the operational task of this manipulator can be implemented, which verify the effectiveness of the proposed method and the correctness of the dynamic model of the underactuated flexible manipulator.

Key words: Flexible, PID, Position control, Underactuated manipulator