Research On A New Structure Of Precision Piezoelectric Linear Stepper Actuator

In recent years, precision actuation is widely used in many fields. As theflourishing development of technology, traditional actuators can not meet therequirements of kinematical accuracy, positioning accuracy, and frequencyresponse. Compared to other materials and actuating methods, piezoelectricactuator has much higher precision and quicker frequency response, and becomesvery popular. This paper designs a precision piezoelectric linear stepper actuatoraccording to the principle of stepper drive. The main contents are presented asfollows:1. IntroductionAt first, the main application fields of precision actuation are introduced. Also,it makes a comparison between some common used kinds of precision actuation,which convinces the PZT actuator has so much advantage. And, three actuationtypes of PZT are introduced and compared. At last, it discusses the currentdevelopment of PZT actuators in and abroad.2. Basic Theory of Piezoelectric MaterialsThis part introduces the basic theory of piezoelectric effect and its relatedfactors. Particularly gives a detail description on piezoelectric stack, about itsstructure and features. And discusses the using method of piezoelectric stack.Found a solid academic foundation for designing the precision actuator.3. Structure Design of the Precision Piezoelectric Stepper ActuatorFirst, describes the basic principle of stepper drive and its working process.Then gives a detail introduction about flexure hinge and fingers out its designprinciples. Makes a theory analysis of flexure hinge, and gains its stiffness equation,analyses the related factors affecting the stiffness. Forms a dynamic model offlexure hinge, and gives it an analytical solution, from which we get the transferfunction and the inherent frequency of the flexure hinge system. What's more,gives a finite solution to flexure hinge, and studies how the structure factors affectthe stiffness and frequency.We also analyses the effect of preload on flexure hinge, and the result showsthat the output of flexure hinge has nothing to do with preload but has a relatinshipwith the stiffness. Also forms a dynamic model of the driving part and gains thetransmit function.According to previous work, designs the structure of a precision linear stepperactuator, and does a lot of work on driving part, clamping part, preload part, runnerand guideway. The outer drive and outer clamping mode, and a vertically clampingform were adopted.4. ExperimentsFirst, introduces the devices used in the experiments, testifies the features ofpiezoelectric stack.Then, testified the characteristics of flexure hinge. The results are presented asfollows:a) In the static test we found that: The preload has some affection on flexurehinge, the larger it is, the larger output displacement obtained. The outputdisplacement gains when the supplied voltage rises up. The factor "t" hasmore affection than the factor "a". There is a big gap between practicalresults and theory results.b) In the dynamic test we found that: Low frequency of supplied power haslittle effect on the output displacement. When the frequency is 1KHz, thetransient response to step signals is quite apparent, and the output isunstable.Then, testifies the prototype of the actuator, mainly about the clampingcharacteristics, driving characteristics, speed, the length of steps, and the loadbearing. The results come out as follows:1) The practical force generated by the clamping part is much smaller thanthe theory result.2) The step get longer and steadier as the voltage rises up.3) The higher frequency, the higher speed.4) The load bearing is up to the force generated by the clamping part., and itis large enough to be used.5. ConclusionMakes a conclusion to the whole paper, and gives some suggestion for futuredevelopment.1) Improve the conditions and methods of experiment, so the operation can beeasier and the results can be more believable.2) Refine the structure of the actuator;make it easier to machine and assemble,and improve the precision and step stability.3) Spend more time to study the basic theory of piezoelectric materials,analysis the affections of hysteresis, creep deformation and nonlinearity.Build up a close loop control system.