Control of a flexible manipulator using a sliding mode controller with a fuzzy-like weighting factor

A sliding mode controller (SMC) is proposed for the tip position control of a flexible manipulator. The authors' objectives are to control the tip to a desired position and to reduce vibrations as much as possible. Vibrations inherited from a light-weight manipulator structure are expensive to measure for feedback control purposes. Here, the authors approximate the vibrations by the first-order dominant mode. The sliding mode controller is employed for its insensitivity to modelling errors. When using a DC motor as the actuator, the system under control behaves as a single input multiple output system; it is difficult to satisfy both control objectives simultaneously. Here, a fuzzy-like weighting factor is imposed on the control signals. When the tracking error is large, tracking will have a higher priority and constitutes a larger portion of the control signal. Suppression of vibration will be effected when the tracking error is small while the portion of the tracking control signal is reduced. Simulation results from open-loop, PID and the proposed controller are included to verify the effectiveness of the proposed method.