Research On Inertial Piezoelectric Actuator And The Actuator Under Magnetic Effect

According to the study of status of inertial drive technology, using the force difference produced by asymmetry gripper drives the piezoelectric actuator. By changing the first nature frequency of bimorph vibrator under the magnetic force in order to achieve the purpose of changing the actuator's velocity. Researched the asymmetry gripper actuator and the cantilever bimorph under magnetic force through deducing in theory, finite element analysis and experimental measurement. The paper consists of the following contents:1. The reasearch and development of piezoelectirc precision actuatorDriven by piezoelectric materials has great advantages over other kinds of drivng ways, such as small volume, high movement precision, rapid response, low power, easy to control. Piezoelectric actuators are divided into three kinds: Direct drive actuator, stepping drive actuator and inertial drive actuator. The inertial drive actuator plays an important role in this field as a result of its particular characteristics. The three types of PZT actuators and the current main application fields of precision actuation are researched in the paper.2. The analysis of the piezoelectirc bimorph and the magnetic mediumStudy the basic theory of piezoelectric actuation. Analyse both the vibration modes of piezoelectric ceramic and the parameters of cantilever bimorph. Both the three principles of piezoelectric inertial drive and the analysis of asymmetry gripper are researched in this chapter. There are three types of magnetic medium: diamagnetic material, paramagnetic material and ferromagnetic material. Because the alloy of ferromagnetic material is easy to be magnetized under the outside magnetic field, and also enhances the magnetic field at the same time, it is suitable for being magnetic effect material. According to the characters of permanent magnet, the Nd-Fe-b is chose for the experiment.3. The reasearch of the vibration of bimorph vibrator and the magnetic forceBecause piezoelectric bimorph vibrator is the most important component of the actuator, its dynamic characteristic is related to the performance of actuator's movement. it is necessary to make an analysis about it. Through the simulation analysis, the normal regulation of piezoelectric bimorph vibrator was obtained: as the mass of inertial body increases, the bimorph vibrator's first nature frequency will reduce but the inertial force will enhance; the deformed value of the end will take a linear change with the excitation voltage. As the actuator involves the magnetic force, the influent factors of magnetic force were studied with the magnetic force formula. Through the finite element analysis, it is found that: when the magnet gets closer to the inertial body, the magnet force increases rapidly; the force will take linear increase when the area and thickness of inertial body increase.The result of the piezoelectric bimorph vibrator dynamic test shows that: the response waveform is still the sine wave when the piezoelectric bimorph vibrator is excited by sine wave voltage, the response waveform is the composition of sine wave with different frequency when excited the square wave voltage. The piezoelectric bimorph vibrator will vibrate through a balance position under the excitation voltage. The smaller the distance of magnet and inertial body is, the lower the first nature frequency of piezoelectric bimorph vibrator is.4. Structure design and experimental research of the actuatorDesign and manufacture the actuator with asymmetrical gripper principle. Considering the convenience of actuator test under the magnetic force, the actuator is designed to drive by only one piezoelectric bimorph vibrator. Testing system is built base on the character of actuator. Some experiments are implemented for piezoelectric actuator to demonstrate its kinematical characteristics such as how the velocities of actuator are affected by driving voltage, frequency and load. The experiment results show that the actuator has a good performance, the velocity and the excitation voltage presents a linear relationship. The increase of load is conductive to the stability of actuator's motion.The actuator with magnetic force is manufactured base on the former actuator. It weighs 107g and driven by one piezoelectric bimorph. Testing the velocity under different voltage, frequency and distance show that magnetic force can achieve the purpose that changes the velocity of actuator. The actuator's former first nature frequency is 15Hz, after changing the distance between magnet and inertial body, the frequency reduces to 13Hz and then 12Hz. The performance of actuator is good. In the range of low voltage, the liner relationship performs well; step is even and moves stably. According to the test, the control method is provided: select suitable working frequency, changing the voltage to realize velocity adjustment.