The hysteresis characteristic of piezoelectric micro-positioning platforms seriously affects its positioning accuracy in precision positioning. It is important to design an effective hysteresis model and control scheme. Based on the analysis of the Duhem model, this paper proposes to divide the hysteresis curve into two parts, the step-up section and the step-down section, to identify the model parameters, respectively, and a hybrid intelligent optimization algorithm based on the artificial fish swarm algorithm and the bat algorithm is proposed. The simulation experiment verified that the error of the improved model was reduced by 48.97%, which greatly improved the identification accuracy of the Duhem model. Finally, an inverse model of the Duhem model for the segmental identification of the improved artificial fish swarm algorithm is established, and a composite controller integrating feedforward, feedback and decoupling control is designed on the basis of the inverse model, and an experimental verification is carried out. The results show that the displacement errors of the composite controller under different voltage signals are all within 0.25%. Therefore, the established model can accurately express the hysteresis characteristics of the platform, and the use of the composite controller can effectively reduce the accuracy error caused by the hysteresis characteristics.
In this paper, a method to calculate the dynamic stress concentration around the triangular defect of piezoelectric material under electroelastic coupling is studied and applied to the promising barium calcium zirconate titanate. Firstly, the electroelastic governing equation is decomposed by decoupling technique, and the analytical solutions of elastic wave field and electric field are obtained by wave function expansion method. Then, the conformal transformation is used to simplify the triangle boundary into a circular boundary, and the corresponding modal coefficients are determined according to the simplified boundary conditions. Finally, the analytical solution of the dynamic stress concentration factor can be obtained according to the constitutive equation. Substitute the relevant material parameters of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 and set different temperatures, Ce doping amount, and incident wave number for numerical simulation. The numerical results show that the incident wave number, piezoelectric properties, and the shape parameters and deflection angle of the triangular defect have a great influence on the dynamic stress around the defect, and some meaningful laws are summarized through analysis.
Flexure hinges manufacturing error and hysteresis nonlinearity of piezoelectric actuator are two key factors that affect control precision of micromanipulator. In order to evaluate error affects on micromanipulator accuracy, a partial differentiation error model of manufacturing error was presented. And the flexure hinges hole radius error, crosssectional width error and minimum thickness error were respectively modeled; besides, we used finite element simulation to validate the analytical error model. The analytical and simulation result shows that the analytical error model is correct, and minimum thickness error induces biggest displacement precision error. In addition, the nonlinear error of piezoelectric actuator was considered, and support vector machine for regression (SVR) was used to model hysteresis nonlinearity. The experiment results show that SVR nonlinear model can accurately describe the nonlinear error. The obtained error model and data are used to establish a theoretical limit for the design and precision control of micromanipulator.
Based on the non-Fourier heat conduction wave model, the thermal wave scattering near the opening in the platinum–rhodium glass fiber leaky plate structure is studied by using complex function method and conformal mapping method, and the general solution of the thermal wave scattering problem is given. The boundary condition of the open surface is adiabatic. The influence of the geometrical and physical parameters of the leaky plate on the temperature distribution in the plate is analyzed, and the numerical results of the temperature concentration are given. This study can provide theoretical basis and reference data for the design and optimization of the opening structure of platinum–rhodium glass fiber leaky plate.
Based on the magnetoacoustic coupled dynamics theory, the wave function expansion method is used to solve the problem of acoustic wave scattering and dynamic stress concentration around the two openings in e-type piezomagnetic composites. To deal with the multiple scattering between openings, the local coordinate method is introduced. The general analytical solution to the problem and the expression of the dynamic stress concentration are derived. As an example, the numerical results of the dynamic stress distribution around two openings with equal diameters are given. The effects of the parameters, such as the incident wave number and the spacing between the openings, on the dynamic stress concentration factor are analyzed.
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