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This paper presents the mechanical design, optimisation and tracking control of a flexure-based positioning stage to generate coupled linear and angular motions. The mechanism employs two piezoelectric actuators, with output translation and rotation proportional to the difference and sum of the input displacements. Computational optimisation utilising finite element analysis is used to develop designs that maximise the working range. A dynamic model is developed, leading to the establishment of a proposed sliding mode controller to allow the stage to track desired trajectories. An adaptive gain is implemented to reduce errors in the estimated kinematics, and accommodate creep within the mechanism. A prototype of the mechanism has been manufactured, and experimentation has been performed to verify computational predictions of the mechanism behaviour. The ability of the proposed controller to execute precise tracking of a desired trajectory within the workspace is demonstrated in the experimental study. [ABSTRACT FROM AUTHOR]

Abstract: Compensations for cross-axis coupling effect and hysteretic nonlinearity of a novel XY piezo-actuated positioning stage are presented in this study. The piezo-actuated stage utilizes a monolithic flexure-based mechanism (FBM) to achieve translations in X- and Y-axes instead of using stacked mechanisms. A hysteresis model with crossover term is proposed to alleviate the cross coupling effect between X- and Y-stages during precision positioning tasks. System identifications using real-coded genetic algorithm (RGA) and clonal selection algorithm (CSA) are compared with particle swarm optimization (PSO). The results show that PSO provides better performance than the others. Therefore, a feedforward controller with cross-axis coupling compensation is studied and the used for the piezo-actuated FBM to enhance the precision of the coarse positioning stage. The experimental results confirm that the proposed controller can achieve precision tracking tasks with submicron precision. [Copyright &y& Elsevier]

Abstract: This paper presents a robust motion tracking control methodology for a flexure-based four-bar micro/nano manipulator driven by a piezoelectric actuator. This control methodology is proposed for tracking desired motion trajectories in view of the problems of unknown or uncertain system parameters, non-linearities including the hysteresis effect, and external disturbances in the system. In this paper, equations of the angular stiffness, ‘static’ linear stiffness, and structural resonance of a flexure-hinged mechanism are presented. In addition, a lumped parameter dynamic model is established for the formulation of the proposed control methodology. The convergence of the position tracking error to zero is assured by the approach in the presence of the aforementioned conditions. The stability of the closed-loop system is proven theoretically, and a precise tracking performance in following a desired motion trajectory is demonstrated in the experimental study. One of the most important advantages of this control methodology is that the approach requires only a knowledge of the estimated lumped parameters in the physical realisation. With the capability of motion tracking, the robust motion control methodology is very attractive in realising high-performance flexure-based control applications in the field of micro/nano manipulation. [Copyright &y& Elsevier]