Study Of Actuators Based On Multiple Piezoelectric Effects

Nowadays, piezoelectric sensors and actuators which have superior performance play a unique role in the national economy and defense industry. The development of modern precision testing and driving technology urgently needs to deepen and extend the piezoelectric theory. Therefore, it's imperative to study the theory and application of multiple piezoelectric effects. This paper, supported by the National Science Foundation under Grant No. 50675026, studies on multiple piezoelectric effects through using the knowledge of different disciplines such as piezoelectricity, physics of dielectrics, physics of crystals, and theory of anisotropic elasticity. And then the microactuator and self-sensing actuator based on multiple piezoelectric effects are developed. The specific work in this paper is as follows.Firstly, according to classical piezoelectric theory, tertiary coupling effect under longitudinal mode of piezoelectric crystal is investigated and the validation methods of tertiary piezoelectric effects are proposed. On the basis of four kinds of piezoelectric equations, the general mathematic models of multiple piezoelectric effects are deduced under applied force and electric field. The experimental results of this tertiary coupling effect of PZT-5 are obtained by the methods that are equivalent to changing boundary conditions. Experimental data shows that the output of tertiary direct and converse piezoelectric effect is linear with the applied force and voltage, respectively. As a result, theoretical analysis is justified by experimental results, just as experimental methods are proved scientific and feasible. Moreover, through a piezoelectric group composed of two xy cutting-type quartz wafers transformed by du, the tertiary piezoelectric effect of piezoelectric quartz which is applied on practical engineering widely is studied. The result of the tertiary piezoelectric effect of piezoelectric quartz is quantified by using a capacitor parallel with the piezoelectric quartz group to eliminate multiple piezoelectric effects. At the same time, the influence of multiple piezoelectric effects on static sensitivity of piezoelectric quartz sensors is obtained. Experimental results show that sensor's static sensitivity is increased by 1.75%. The influence of multiple piezoelectric effects on the stiffness, natural frequency and electromechanical coupling factor of piezoelectric quartz force sensors is analyzed.Secondly, the microactuator based on multiple piezoelectric effects of PZT stack is developed. The principle of microactuator based on these effects is demonstrated. Its theoretical feasibility is validated through the experiment. After choosing the core element, structural form and pretightening mode of the microactuator, a simplified mechanical model of the microactuator is established. According to the model, the actuation plate and shell of microactuator is analyzed and designed. In this way, the size parameters of each component are obtained. The functionality of component parameters' selection is further validated through FEM analysis. Finally, the microactuator based on multiple piezoelectric effects is developed successfully. The results of static calibration show that there is a strong linear relationship between the output voltage, elastic displacement and output displacement of the secondary converse effect of the microactuator and external loading. In this dynamic calibration, natural frequency of the microactuator is 4.433KHz. The microactuator not only can realize dual-stage position of elastic displacement and secondary converse displacement, but also can check the external loading through the primary direct piezoelectric effect of the microactuator.Thirdly, the research of the piezoelectric self-sensing actuator is performed on the basis of multiple piezoelectric effects and the decoupling method of self-sensing actuator based on multiple piezoelectric effects is proposed. Through a referenced capacitor combined with current integration and a differential proportional operational circuit, this self-sensing experiment of displacement of a PZT-5 actuator is performed. The experimental results indicate that multiple direct piezoelectric effects generated by the piezoelectric actuator itself may totally reflect the information of the output displacement of actuator. Meanwhile, it proves that the decoupling method is correct. Consequently, a decoupling method that is easier for practical engineering application than electric bridge circuit is obtained. Through adopting the microactuator based on multiple piezoelectric effects of ceramics, the experimental research of self-sensing of displacement of the microactuator is performed. Experimental results further show that the self-sensing method based on multiple piezoelectric effects may well acquire the signal of the output displacement of the microactuator.