Visual Servo Control System of a Piezoelectric2-Degree-of-Freedom Nano-Stepping Motor

Model-Free Adaptive Positioning Control of the Bidirectional Stick-Slip Piezoelectric Actuator with Coupled Asymmetric Flexure-Hinge Mechanisms

A model-free adaptive positioning control strategy for piezoelectric stick-slip actuators (PSSAs) with uncertain disturbance is proposed. The designed controller consists of a data-driven self-learning feedforward controller and a model-free adaptive feedback controller with a radial basis function neural network (RBFNN)-based observer. Unlike the traditional model-based control methods, the model-free adaptive control (MFAC) strategy avoids the complicated modeling process. First, the nonlinear system of the PSSA is dynamically linearized into a data model. Then, the model-free adaptive feedback controller based on a data model is designed to avoid the complicated modeling process and enhance the robustness of the control system. Simultaneously, the data-driven self-learning feedforward controller is improved to realize the high-precision control performance. Additionally, the convergence of the tracking error and the boundedness of the control output signal are proved. Finally, the experimentally obtained results illustrate the advantages and effectiveness of the developed control methodology on the bidirectional stick-slip piezoelectric actuator with coupled asymmetric flexure-hinge mechanisms. The positioning error through the proposed controller reaches 30 nm under the low-frequency condition and 200 nm under the high-frequency condition when the target position is set to 100 μm. In addition, the target position can be accurately tracked in less than 0.5 s in the presence of a 100 Hz frequency.

Finite Element Analysis and Polarization Test of IDEs Piezoelectric Actuator

A new type of actuator is presented in the paper that integrates the IDEs into a conventional piezoelectric sheet. The electrodes and polarization play a key role in the strain. Adopting constitutive equations of piezoelectric theory and variation principles in elasticity theory, the piezoelectric component dynamic equation was deduced. Several finite element models of the IDEs piezoelectric actuator were established in ANSYS. The effect of branch electrodes on the strain of the actuator was analyzed. The results show that the strain can be bigger than that of the conventional piezoelectric sheet by decreasing the gap and increasing the width of electrodes. According to the FEM result, some IDEs piezoelectric actuators were prepared. The distribution of the static electric field inside the actuator was researched to determine the polarization voltage. The 2671 high voltage power and DU-20 temperature-controlled oil bath was applied to explore the polarization process. The effect of the voltage, time and temperature on the strain of the actuator was researched by a TF2000 and SIOS laser interferometer. The results show that the optimum polarization is 800 V, for 60 min and at 150 °C. The strain of the IDEs piezoelectric actuator is 1.87 times that of the conventional piezoelectric actuator. The actuators could prove to be helpful applications for micro-nano devices.