Research On A Linear Actuator Driven By Single Piezoelectric Vibrator Based On Impact Principle

With the development of science and technology the demands of small drive are growing.Piezoelectric actuator has a prominent role in achieving short response time, high precision andlarge displacement because of its advantages such as short response time, large displacement,little volume, high energy conversion efficiency and simple structure etc.A new method is proposed to realize the inertial impact movement by changing thepressure between the actuator and the contact plane, which changed the friction of differentdirections according to the friction principle. Based on the principle of inertial impact, a linearactuator driven by single-piezoelectric-vibrator is designed and researched. Experimentationsare carried on to know its performance. The details are described as follows:1. The basic principle of piezoelectric ceramicThe basic principle of piezoelectric ceramic and different kinds of piezoelectric actuatorare discussed to know the piezoelectric drive better before actuator is designed, which suppliedtheoretical dependence for the selection of piezoelectric actuators and the design of them. Thepiezoelectric ceramics' basic nature such as the piezoelectric effect and the counterpiezoelectric effect are introduced here, too. Piezoelectric material is a kind of elastomers, sodifferent independent variables can be chosen under different boundary conditions, one of the 4piezoelectric equations is put forward in this paper.2. Design of linear actuator driven by piezoelectric ceramicA piezoelectric vibrator is fixed on the trapezoidal block's incline, thus it produces inertialforce to change the pressure between the actuator and the working plane, which changes thedriving force and the friction force at the same time to change the state of movement. Theincline design merits lie in: When the piezoelectric vibrator produces upward inertial force, itshorizontal component and vertical component achieve the biggest value at the same time,which means when driving force reaches its biggest the work plane's friction reaches thesmallest value. The actuator gets big acceleration;In the same way, when the piezoelectricvibrator produces downward inertial force, its horizontal component and vertical componentachieve the biggest value at the same time, which means when driving force reachesits biggest the work plane's friction reaches its biggest value, too. The actuator gets smallacceleration. Thus, the actuator is obvious to move right with only one piezoelectric vibrator.3. Tests on piezoelectric ceramic performancesThe performances of voltage-displacement, frequency-displacement under sine-wave andsquare-wave and their movement are tested,as well as its base frequency with ANSYSanalyzing. Only by its finite element analyzing can we effectively get the actuator's vibrationmodels to analyze and control the movement of the linear actuator better.4. Test and research on the piezoelectric linear actuatorThe speed of the linear actuator is tested mainly.First, the movement of the actuator under different symmetrical waves like sine-wave,triangle-wave and square-wave are tested to know its performances under different conditions.It is discovered that the actuator can move only when it is actuated by the 13, 14Hztriangle-wave. It is not easy to be controlled;the actuator's displacement responds linearlyunder the sine-wave well. Although the actuator can be controlled easily, force it produces islimited;the actuator can move stably from low frequency to high frequency under thesquare-wave. Force is big when the piezoelectric vibrator actuated by square-wave.Then, the relation of piezoelectric cantilever's end displacement and actuator'displacement is got. A cuneal mechanism is proposed to increase its reverse friction modulus todecrease its reverse friction. Experiments show that the actuator can move linearly undercontrol with optimized structure and changeable voltage.Finally, a piezoelectric multilayer actuator's velocity performance is tested. It movesfrequently under different frequencies and voltages actuated by limited driving force.Experiments above prove that the actuator designed has good performances, it can realizequick response, big driving force and big stroke actuation, which lays the foundation foractuators' further development.5. ConclusionsThis article's main research content and conclusions are as follows:1. The piezoelectric ceramics' basic nature such as the piezoelectric effect and the counterpiezoelectric effect are introduced and one of the 4 piezoelectric equations is put forward in thispaper. We choose 2 piezoelectric ceramics: the piezoelectric cantilever and piezoelectricmultilayer as actuators, whose structures and characteristics are told.2. Based on the principle of impact, a new principle is proposed and the emulation modelof the linear actuator driven by single-piezoelectric-vibrator is built to analyze its movementunder square-wave with software Matlab. And by the simplification of mechanism's dynamicsmodel, the condition of the actuator's movement is obtained. A mechanism which can changethe angle of the incline is designed to know its effect to the actuator's performance byexperiments. The actuator can realize stable movement under square-wave theoretically. Thesetheoretical results help the mechanism designs and experiments.3. A linear actuator driven by single-piezoelectric-vibrator is designed, which can movelinearly actuated by only one piezoelectric-vibrator. Its velocity performance can be controlledby changeable frequencies and voltages. The design of the actuator satisfied the need ofexperiments.4. A cuneal mechanism is proposed to change its friction by changing its friction modulusand pressure at the same time. Experiments show that the cuneal mechanism can move fasterthan the actuator without the cuneal part.5. Analyzed the static performance of the Tokin AE0505D16 piezoelectric multilayeractuator with Ansys, as well as the mode of the piezoelectric cantilever. Carried on the testsunder different voltages, different frequences, different waves and so on to get its dynamiccharacteristic and obtain its movement characteristics of the piezoelectric vibrator, whichhas provided theory basis for the precision driver design.6. Set up the integrate test system using the wave generating apparatus, the poweramplifier, the laser position finder and the Fourier analyzer to test the inertial movementperformance. The tests indicated that, this actuator has good performance. It can realize highaccuracy 1μm , fast localization 2mm/s and two times weight of itself load added. Itsmovement distance is infinite theoretically, only restricted by the wire length and the contactplane size.But it also needs further work to improve the aspects below:1. Based on the emulation model we have, the friction model between the actuator and theplane needs to be built to emuluat the movement with Matlab. The model should be more closeto the real working condition to instruct the mechanism design.2. Closed loops system needs to be established. High accuracy position transmitter or themetering equipment needs to be installed to get the real-time feedback. By this way the actuatorcan be controlled precisely. A more effective control of the linear actuator driven bysingle-piezoelectric-vibrator is carried on and its application will be promoted.