TRAJECTORY TRACKING CONTROL WITH SPECIFIED POSTURE FOR PLANAR FOUR-LINK REAL UNDERACTUATED MANIPULATOR

A fuzzy control strategy is proposed for a planar four-link active-passive-active-active (APAA) real underactuated manipulator (RUM) to realize the control objective, which is to make the RUM track at a given trajectory with a specified posture. Employing a kinematic model of the manipulator, we obtain the constraint between the position of the end-point and all link angles, and the constraint between the posture of the fourth link and all link angles. We let the first link to remain in uniform motion, so the end-point of the manipulator can get a velocity in the direction of the trajectory. Meantime, we design fuzzy controllers for the third link and the fourth link to make the end-point of the manipulator track the target trajectory and stabilize the fourth link in the target posture, respectively. The proposed control strategy is applied to the real system. The experiment results show that the proposed control strategy is effective and exhibits good robustness.