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...