Theoretical And Experimental Research On A Piezoelectric Self-Sensing Actuator Utilizing Inertial Impact Force

Since the 20th century, the microelectromechanical system (MEMS) develops fast with the rapid development of modern technology. The nanotechnology has become the key technology as an important part of MEMS. Meanwhile, new kinds of multi-functional materials emerge in material field such as mechanical and hydraulic, pneumatic, assolenoid style functional materials, which are used as the actuator material to reach high motion precision. But the traditional mechanical transmission has bigger mechanical clearance, friction and creeping, for which micro/nano level precision can't be got easily. The hydraulic, pneumatic and assolenoid style actuators have big inertial force, complicated structure, slow response and low reliability. So the piezoelectric ceramic actuators are widely used in the micro positioning field with high resolution, quick response, big structure stiffness and small size advantages.The piezoelectric ceramic materials used as actuators are widely adopted in the piezoelectric precision driven field. Many kinds of piezoelectric actuators come out based on different working principles and structures with the development of the piezoelectric technology. According to different working principles the piezoelectric actuators can be divided into 3 types: direct-acting piezoelectric actuator, stepped piezoelectric actuator and impact drive piezoelectric actuator.The impact drive piezoelectric actuator is the research object in the thesis. According to the national 863 project and the natural science foundation requires, a new kind of impact drive piezoelectric actuator is proposed, which is actuated by symmetric wave signal. The pressure force of the actuator and the friction force between the actuator and interface change at the same time when the piezoelectric bimorphs are actuated by the symmetric wave. With different friction force and the same actuation force the piezoelectric actuator realizes linear displacement. Based on the above basis, decoupling air-separation multiplexing self-sensing method is analyzed, by which the piezoelectric bimorphs'vibration is controlled actively. The experimental system is built and the active control effect is inspected which provide a simple and effective method to eliminate the residual oscillation. The main research contents are as follows:1. The research status and the application prospect of domestic piezoelectric actuators are analyzed. A piezoelectric self-sensing actuator utilizing inertial impact force based on the self-sensing technology is put forward. The piezoelectric equation and two-way exchange matrix are got based on piezoceramics theory and bilateral transducer theory, which provides theretical basis for its application. The piezoelectric bimorph oscillator's FEM (finite element analysis) model is established, on which the piezoelectric bimorph oscillator's vibration modal, piezoelectric output characteristics and converse piezoelectric output characteristics are analyzed. And the piezoelectric bimorphs'self-sensing voltage is induced when force is actuated on its free end, which provides the basis for the self-sensing structural design.2. The impact movement mechanism that the piezoelectric actuator actuated by the symmetric wave signal moves is analyzed. When the piezoelectric actuator is actuated by the symmetric wave signal the positive pressure changes and the friction force between the actuator and interface changes. Combining with the constant driving force, the actuator moves along the proposed direction. The impact force model and its test system are established to analyze the impact force's value quantitatively at the first time. The theoretical impact force model of the piezoelectric bimorphs oscillator is built to analyze its influence factors using Matlab. The inertial impact force test system is established to test the inertial force value under different symmetric wave. The square wave a kind of symmetric waves'characteristics comparing with sine wave and triangle wave is testd. And the inertial force's change rules of the piezoelectric bimorphs oscillator under different frequencies, different test voltage amplitude and different deformation are tested, which provides basis for the wave use.3. The piezoelectric ceramics'sensing properties are studied. The self-sensing piezoelectric actuator with integrated structure is proposed in the paper. The piezoelectric ceramics'deformation is got using the piezoelectric output characteristics. The bimorphs'inductive voltage characteristics and variation's distributions piecture are studied using ANSYS. Then experimental methods are used to test its changing rule, which provides the theory basis for the piezoelectric sensing ceramics'using.4. Firstly, an inertial linear actuator actuated by the symmetric wave signal is proposed. When the piezoelectric actuator is actuated by the symmetric wave signal the positive pressure and the friction force between the actuator and interface change. Then based on the above basis, the other inertial rotation actuator is proposed with the changing combining of the friction torque and drive torque. The piezoelectric bimorphs oscillator is put tipsily in the 2 piezoelectric actuators'structure, which change the positive pressure and the friction force at the same time. The inertial actuators realize the proposed direction movement actuated by only a pair of piezoelectric bimorphs oscillator with simple structure. The inertial actuators'movement condition and the velocity's affect factors are analyzed in theory. And the actuator's movment rule is analyzed theoretically with the dynamic model built using Matlab, which illustrates the feasibility of the scheme.5. Based on the above inertial impact principle, 2 kinds of piezoelectric inertial actuators structure are put forward: an inertial linear actuator and an inertial rotation actuator. The actuator's experimental test system is built to anaylize the 2 actuators'displacement output characteristics such as step, speed, resolution and load capacity, etc. Theoretical analysis and experimental results correspond.6. The active control system of the piezoelectric self-sensing actuator utilizing inertial impact force is researched. The linear quadratic optimal control algorithm is studied and the optimal control equation is obtained. The optimal control force value is deduced to make the piezoelectric bimorphs oscillator eliminate the residual oscillation more quickly. The control system is applied to the piezoelectric actuator and the piezoelectric self-sensing actuator's position precision is promoted, which confirms the decoupling air-separation multiplexing method of piezoelectric sensor theory in the application of inertial drive.The main innovation of the research work:1. The piezoelectric actuator adopts the inclined plane, on which the piezoelectric bimorphs oscillator is fixed. When the piezoelectric actuator is actuated by the symmetric wave signal the positive pressure changes and the friction force between the actuator and interface changes. Combining with the constant driving force, the actuator moves along the proposed direction. Different from the asymmetric wave drive, the piezoelectric actuator realized the proposed movement using only a pair of the piezoelectric bimorph oscillator. The electric circuit is simple, too. The piezoelectric actuator is easier to get bigger and higher precision displacement.2. The bimorph's inertial force is analyzed quantitatively. The influence factors of the inertial force produced by the piezoelectric bimorph oscillator are researched qualitatively. The impact force's experimental system is established and its value variation rule is studied.3. By the finite element method, voltage induced characteristics and its distribution are analyzed by the force acted on the end of the piezoelectric bimorph, which provides a basis on piezoelectric structure design. For the first time, the piezoelectric self-sensing structure is applied to the piezoelectric inertial actuators. By piezoelectric inertial air multiplexing method the bimorph's residual concussion eliminates more quickly. The inertial force that makes the actuator move back is inhibited, which improves the drive accuracy.In brief, the impact movement mechanism that the piezoelectric actuator actuated by the symmetric wave signal is proved feasible and correct by the theoretical analysis and experimental research of the piezoelectric bimorph, the experimental prototype design and its experimental analysis. The piezoelectric actuator obtains high speed and displacement resolution, which provides new ideas and methods for the piezoelectric inertial actuator's research.