Electromechanical Coupling Characteristics Analysis And Experimental Research Of Novel Piezoelectric Device

Piezoelectric material is viewed as the core of the electromechanical energy conversion for piezoelectric device. And with the advancement of electronic scientific and material scientific technology, they are rapidly developed in the direction of integration, microminiaturization, intellectualization, light-weight and low-power consumption. And there are some new piezoelectric devices, such as piezoelectric energy harvester, piezoelectric ultrasonic actuator, piezoelectric vibration sensor and so on. These novel piezoelectric devices have been widely applied in wireless sensor networks, portable electronic equipment and precision drive and control system.In the low-power micro-electronic products like wireless sensor networks and portable smart devices, the conventional electrochemical battery is increasingly highlighted the shortcomings of the short life, the environment pollution and regularly frequent replacement at present. Therefore, a new sustainable and non-polluting energy must be studied as the substitute of the electrochemical battery, because the supplying power of the micro-electronic products has become the current bottleneck problem addressed urgently. One of the effective ways to deal with the problem is the application of piezoelectric energy harvester based on direct piezoelectric effect. This new piezoelectric device has attracted the interest of the majority of scholars, because it has some characteristics of no electromagnetic interference, green environment, high energy density and small size. Meanwhile, some researches have been mainly made about the structural design, the vibration mode and the energy harvesting circuit, but haven’t always been involved in impedance optimization between energy harvesting circuit and piezoelectric ceramic. Due to this, a large of energy is lost to make energy conversion rate lower. Moreover, piezoelectric ultrasonic motor is another piezoelectric device to achieve the driving function under the converse piezoelectric effect. The motor is capable of precision positioning and favorable control performance and has naturally replaced the traditional electromagnetic motor in many fields. Be that as it may, most of the energy is lost in the form of heat so that the energy is greatly dissipated and the output power is much lower than the fifty percent of the total energy. Therefore, how to effectively improve their output power and reduce energy loss is the key technical problem to be solved. The paper chooses piezoelectric energy harvester and piezoelectric ultrasonic motor as the object of study. For piezoelectric energy harvester, the typical piezoelectric energy harvester is designed. Considering the structural factor and electromechanical coupling factor comprehensively, the research and analysis is carried out about the piezoelectric energy harvester with ADPL command stream. And thus, the optimization of output power is also realized, which provides impedance basis for the design of energy harvesting circuit. Simultaneously, aiming to the defects of single resonance frequency and narrow operating band in the aforementioned energy harvester, the broadband piezoelectric vibration energy harvester with an elastic amplifier is proposed. Its finite element electromechanical coupling analysis model is built, and the impact of structural parameters on the output performance is also analyzed. And then its physical prototype is developed and the detailed experimental study is made by setting up the related experiment system. For piezoelectric ultrasonic motor, the energy feedback type ultrasonic motor with driving function and energy harvesting function is designed by combining the principle of energy harvester and improving division mode of the ring piezoelectric crystal. The electromechanical coupling finite element model of its stator is established to analyze the effect of the stator’s structural parameters on the vibration and electric output properties. Research contents of this paper are arranged as following:The first chapter describes its background and significance, and formulates the classification and the application of piezoelectric device. And thus it also reviews the current situation of piezoelectric vibration energy harvester based on the direct piezoelectric effect and the piezoelectric ultrasonic motor based on the converse piezoelectric effect from home and abroad. Finally, the chapter points out the problems and deficiencies in the research.The second chapter focuses mainly on the basic theoretical knowledge, related to the thesis research work, including the piezoelectric ceramics, piezoelectric effect, piezoelectric equations and vibration theory. The cantilever piezoelectric vibration energy harvester model and the ring sandwich piezoelectric vibrator model are built on the basis of the foundational theory. At the same time, their differential equations of bending free vibration are derived from Euler-Bernoulli beam theory respectively. On this basis, their mode shape function, frequency equation and vibration modal are calculated.The third chapter studies the structural design and working principle of the cantilever piezoelectric vibration energy harvester, and explains in detail the establishing process of electromechanical coupling model through the ADPL command stream. Then, the effect of load resistance on the vibration characteristic and the electrical output characteristic is analyzed to realize the optimization of output power and the design and obtain the optimal matching resistor. Finally, there are two forms of electrode connection containing series and parallel, of which the impact on the cantilever energy harvester is also studied and analyzed.The fourth chapter makes an emphasis on the design and the force-electrical output characteristics of the broadband piezoelectric vibration energy harvester. The broadband piezoelectric vibration energy harvester with an elastic amplifier is put forward. And then allowing for some coupling relations (for example, cantilever and circuit, cantilever and spring system), its electromechanical coupling model is established by ADPL command stream. After that, the effect of mass ratio, stiffness ratio, damping ratio and load resistance on its force-electrical output characteristics is also studied in detail. Meanwhile, the chapter carries out the detailed analysis and study about the power optimization and the impedance matching.The fifth chapter investigates the energy feedback type ultrasonic motor which belongs to a new piezoelectric device under the condition of the converse piezoelectric effect. The motor is provided with both precise actuating function and energy harvesting function. The chapter details the structural design idea of the ring sandwich piezoelectric vibrator. Simultaneously, the electromechanical coupling model is built with the finite element method to analyze the vibration characteristics and the electrical output characteristics. Moreover, a research is also made about the influence of different converting circuit topologies on the vibration and the energy transformation performances of the piezoelectric vibrator.The sixth chapter develops sample models of the single-frequency cantilever energy harvester and the broadband vibration energy harvester. Subsequently, the chapter sets up an experimental platform for them and details the operational process of the experimental system. Finally, the chapter validates the correctness of finite element simulation results by the way of analyzing experimental data.