| Linear ultrasonic motor(LUSM) has characteristics of non-electromagnetic interference, simplestructure, flexible design, in particular, it is easy to obtain linear motion with high positioningaccuracy and so is paid more attention to in wide industry. Recently there is considerable progress ofLUSM on basic theory research and application research, and the technologies of LUSM in Germany,Japan, the United States, Israel and other developed countries have been employed to the stage ofindustrialization. Some of the products give a strong support to enhance the performance of some hightechnology equipment. Although the technologies on LUSM have made great progress in china bymuch more efforts in recent years, there is still a large gap from practical applications.This research is supported by the key projects of National Natural Science Foundation of “Basicstudies on piezo precision driving technology”(No.50735002). Choosing the multi-driving-patternLUSM with tower-shaped stator to study, the author designed three prototype motors with differentstructural tower-shaped stator; according to the comparative study between their different driving lawswith relative output performance, the characteristics of the micro-stepping is revealed, and thehigh-precision positioning control method is built up, as the foundation for micron-positioning ornano-positioning technologies of the tower-shaped LUSMs in the case of large stroke control. Toconclude, main research contents and achievements of this dissertation are as follows:1. The research status and the history of the development in LUSM are reviewed, and thecharacteristics of LUSM are summarized. that linear ultrasonic motor is of great significance for thedevelopment of modern science and engineering technology. The existing tower-shaped LUSMs andmulti-driving-pattern LUSMs are summarized and analyzed, obtaining a clear research objective ofthis subject. In accordance with the theoretical motion trajectory of the driving end on USM, theclassification of USM is completed, and this classification method is easier to unify manifold drivingpattern and driving mechanism of USM. On this basis, it is provided by the author that the motiontrajectory of the driving end is divided into two processes: push part and return part, and a new energytransfer analysis method is obtained by comparing the push part’s acting with the return part’s acting.Through the energy transfer analysis of ultrasonic motor, the energy transfer laws of every types ofultrasonic motors are gotten.2. The relative issues of dual-mode-driving LUSM are researched, including the design ofUSM’s operation modes of different mode shape, modal frequency harmonizing method in the contact boundary conditions, the stator’s supporting method, pre-pressure applying method and its influenceon the optimal operating frequency of the stator. A mode-control-uncoupling LUSM with atower-shaped stator is designed and manufactured. The support structure of elastic support withabrupt changing configuration is designed to release the impact of the stator’s supporting on theUSM’s operation modes; the optimum operating point of the mode-control-uncoupling LUSMworking in the resonance mode is obtained by testing the relationship between working modalfrequency and pre-pressure;a universal one-dimension and LUSM-driving precision moving stagebased on three roller structure are designed.3. The design method of a kind of USM with inclined rotor are put forward, and asingle-mode-drive bi-direction-moving LUSM composed of an inclined slider and a tower-shapedstator is designed and manufactured. The working principle and the design principles of the motor areanalyzed, and the obliquity range of the inclined slider which can make the motor running normallywas derived,which provides a theoretical basis to the farther research and engineering design of theinclined-rotor USM.4. The mode-conversion phenomenon of a tower-shaped stator arise from asymmetrical structureis discovered, and a single-mode-drive bi-direction-moving LUSM composed of a tower-shaped statorwith asymmetrical structure is designed and manufactured. The working principle of theasymmetrical-stator LUSM is analyzed, which provides a theoretical basis to the farther research andengineering design of the asymmetrical-stator LUSM.5. According to the features of and the mode-control-uncoupling LUSM and theasymmetrical-stator LUSM, four operating patterns are designed. The four operating patterns include:the resonant and continuous-moving pattern, the nonresonant and continuous-moving pattern, theresonant and step-moving pattern, the nonresonant and step-moving pattern. A large strokemicron-positioning or nano-positioning method is provided by a combination of the four operatingpatterns. The experiments show that the two motors can realize high speed moving in the resonant andcontinuous-moving pattern, and can realize low speed moving in the nonresonant andcontinuous-moving pattern, and can realize nano-scale(<100nm) step moving in the resonant andstep-moving pattern, and can realize nano-scale(<100nm) step moving in the nonresonant andstep-moving pattern. So the combination of the four operating patterns can sufficiently exert the twomotor’s ability to precise positioning, and this idea can be extended to other types of LUSM.6. According to the relationship between the stator’s vibration energy and energy threshold,USMs’ transient characteristics and dead-zone characteristics are analyzed, and come to the following conclusion: an USM’ step distance is dependent on its transient characteristics, and an USM’sminimum step distance is dependent on its dead-zone characteristics. An experiment on the dead-zonecharacteristics of the mode-control-uncoupling LUSM has been carried out. From the experiment it isfound that the dead-zone velocity exists. The phenomenon of the existing dead-zone velocity provethat an USM’s minimum step distance has an extremum. A statistical analysis of themode-control-uncoupling LUSM’s and the asymmetrical-stator LUSM’s experiment data on thenano-scale(<100nm) step moving is made, and LUSM’s characteristics of nano-scale(<100nm) stepmoving are obtained. Three main factors to limit LUSM’s smallest step are revealed to propose themethod for the further reduction of the minimum step of LUSM. |
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