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Online tuning of dither for micro-nano positioning platform: A PID based approach

Piezo-actuated platforms are used in several nano positioning applications because of their high resolution, large blocking force, high stiffness constant and quick response. But the intrinsic hysteretic nonlinearity considerably dampens their performance. Dither based control is known to ameliorate hysteresis in piezoelectric actuators. However, due to parametric variations and uncertainties, dither control alone cannot achieve the desired positional accuracy. In order to effectively implement any real-time control to alleviate the effects of nonlinearity, an adaptive mechanism is the utmost priority to update the control system. This paper explores the effects of hysteretic nonlinearity in a second order Dahl model based piezo-driven manipulator. The plant performance is known to improve with a suitable amount of injected noise. The concept of dither based control is cascaded with the conventional PID controller to bring out an innovative adaptive voltage control strategy. A dual axis piezo platform is taken into account for the controller design and validation. The performance of the controller is verified using certain tests. Results show an improved positioning accuracy of the manipulator with the proposed control scheme than without it. The proposed control emerges as an effective control strategy to improve trajectory tracking accuracy.