Modeling And Analysis Of A Novel Piezoelectric-film Driven Micro-positioning Stage

Micro/nano positioning technology has become one of the common key technologies in modern precision industries including nano manufacturing,high resolution imaging, lithography machining of semiconductors, and high density data storage. With rapid developments of these precision engineering areas, significant technical challenges have been posed for the performance and structure of the micro/nano positioning systems. In particular, the micro-positioning stages with compact structures, multi-dimensional motions and fast responses have been essential for some emerging industries, such as endoscopic optical coherence tomography and high density optical storage. However, traditional piezo stack actuators cannot be applied to these areas due to the limitation of the size. Consequently, piezoelectric thin film actuators with compact structure, high energy density, high reliability, high resolution and fast response, have attracted significant research efforts in these emerging areas. In this thesis, we design a novel 3-DOF (degree of freedom)piezoelectric-film driving micro-positioning stage based on flexure hinge structure and piezoelectric thin film actuator. Through elastic deformation, the micro-positioning stage generates roll, pitch and z-axial translation, with the advantages of compact structure, shock-free and frictionless. Research efforts have been made on the design,modeling and simulation of the piezoelectric thin film actuator and piezoelectric-film driving micro-positioning stage. Detailed research works are as follows:Firstly, based on electromechanical coupling characteristic of piezoelectric material,the driving principle of piezoelectric thin film actuator is studied. Accordingly, an improved theoretical analysis model of piezoelectric thin film actuator has been established on the basis of Euler-Bemouli beam theory and the piezoelectric constitutive equation under force balance conditions. Considering the location and length of the piezoelectric film, and the position and different forms of the load, the driving model of the piezoelectric film beam under normal conditions is deduced. Furthermore, the dynamic response equation of the piezoelectric thin film beam is obtained according to the beam free vibration model.Afterwards, a flexure hinges-based 3-DOF (degree of freedom) micro-positioning stage is designed, which is driven by piezoelectric-film actuators. The corresponding static and dynamical modeling methods are also proposed for purpose of mechanical performance evaluation and optimization. In particular, the compliance model of the micro-positioning stage is first derived based on the matrix method. By incorporating the piezoelectric-film beam model and the mechanism compliance model, the output model of the micro-positioning stage is then established. Moreover, the micro-positioning stage is simplified as a multi-degree-of freedom spring-mass model.According to the Lagrange's second type equation of the complete system,the dynamic model of the micro-positioning stage is further established.Eventually, the finite element simulation method is adopted to verify the proposed theoretical modeling methods of piezoelectric thin film actuator and the micro-positioning stage. The characteristics of the piezoelectric thin film actuator and piezoelectric-film driving micro-positioning stage is analyzed by FEA(finite-element-analysis), which agrees well with the theoretical computation results.The comparison results demonstrate the effectiveness and the accuracy of the proposed modeling method, which provides a guideline for the design and optimization of the piezoelectric-film driving multi-dimensional micro-positioning stage.