This paper proposes an enhanced sliding mode controller (SMC) for piezoelectric actuator based flexural mechanism (PABFM) to track desired motion trajectories. First, based on the variable structural control approach, the proposed controller is established to accommodate parameter uncertainties, nonlinearity, and unmodelled disturbances. Because the traditional sliding-mode control cannot deal with mismatched disturbances effectively, a hysteresis counterelectromotive force (CEMF) model is proposed to describe nonlinear hysteresis effect and electric-mechanical coupling of PABFM. as Similar to the CEMF voltage for a motor caused by a changing electromagnetic field due to a rotating armature, the CEMF voltage appears to PA due to polarization and molecule friction of piezomaterial. The CEMF model is identified using a charge system search (CSS). Then, the proposed SMC with CEMF compensation is studied to deal with the mismatched nonlinear disturbances. To check the consistency of the proposed SMC controller with CEMF compensation, the simulation results were compared with the experimental results. The real-time implementation validated the tracking error better than the traditional SMC.
A low-cost device is presented for noncontact measurement of robot position and orientation. It consists of an optical sensor and three laser scanners. The sensor is attached to the end-effector while the laser scanners cast light planes to trace the sensor movement. The device measures equations of the light planes from which end-effector position and orientation are obtained. Accurate measurement is achieved in a three-DOF experiment.Index Terms-End-effector position and orientation, noncontact measurement, robot calibration, robot metrology. Publisher Item Identifier S 1042-296X(99)04180-4.
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