Abstract: Based on the fuzzy control theory, the position and orientation control of a 4-DOF planar underactuated robot is investigated. The 4-DOF planar underactuated robot is a complex second order non-holonomic system with redundancy and underactuation. Using the coupling effect between the acceleration of passive joint and that of active joints, the motion of the passive joint is controlled. The trajectory tracking of end point and the orientation control of end link of robot are achieved simultaneously. A double fuzzy-PID compound controller is designed for the two subtasks based on the hierarchical control idea. The controller is verified by the co-simulation in Matlab and ADAMS. The experiment of the position and orientation control of the 4-DOF planar underactuated robot is realized on the experimental test bed based on PMAC controller. The results of simulation and experiment indicate that the fuzzy-PID compound controller is feasible and effective for the position and orientation control of 4R horizontal underactuated robot.

Key words: 4-DOF, fuzzy control, position and orientation control, underactuated robot