Research On A 3-DOF Planar Micro-Motion Stage Based On Piezoelectric Actuators

Micro-motion stage is an integral part of the research for the precise positioning technology. Stages that with high precision can obtain good performance in terms of resolution, positioning accuracy, stiffness, stability, etc. Therefore, micro-motion stages are widely used in a variety of situations that require high precision. This research focuses on a planar 3-DOF micro-motion stage based on piezoelectric actuators.Piezoelectric actuators are most commonly used in micro-motion stages. The hysteresis characteristic of the actuators is the most important factor that influences the positioning accuracy. In order to obtain higher accuracy, this research builds PI hysteresis model and identifies parameters of the model by adaptive PSO algorithm. Because of the asymmetry of the hysteresis curve, PI model cannot achieve desired accuracy. Thus, a new method of model construction is proposed. The results show that the proposed method can make the model accuracy improved significantly.Pseudo-body model and FEA method are used for the analysis of displacement, velocity and workspace of the stage respectively. Thus, we obtain the displacement transfer matrix, Jacobian matrix and calculate the workspace of the platform. Analysis shows that the shape of the workspace is a regular hexagon.Statics and dynamics properties are studied. The rotational stiffness of the flexible hinge are obtained and used to calculate the stiffness of the whole stage. Lagrangian method is used to build the dynamic model of the micro-motion stage. Formulas for kinetic energy and potential energy are established. First three natural frequencies of the stage are calculated. ANSYS simulation and modal test are used to verify the correctness of the calculation.Finally, experimental system of the stage is set up. By using frequency laser interferometer, the actual displacement of the piezoelectric actuator is measured. Moreover, Jacobian matrix is corrected according to the measurement. Based on fuzzy PID controller, control system of the stage is built. According to the experimental results, factors that may cause errors are analyzed.