外文翻译--各类超声电机的工作原理的介绍【中英文文献译文】
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各类超声电机的工作原理的介绍K . SpannerPhysik Instrumente GmbH & Co. KG, Karlsruhe, Germany摘 要超声压电电机问世已经超过30年。特别在近年，许多旋转和直线运动的设计已经发展起来了。本文主要介绍超声电机的定义和各类超声电机的工作原理。针对于市场上的各类超声电机解析其工作原理及其利弊。本文主要让大家熟悉目前超声电机的发展背景。 关键字：压电电机；PZT；超声电机；行波；驻波；压电振子 引言 现在有许多利用逆压电效应产生运动的设计理念。超声电机正是逆压电效应应用一类典型实例。 这些电动机具有低速大转矩，定位精度高的特性。正因为它具有的这些特性，使许多公司对于它的研究具有非常溶厚的兴趣。压电电机 压电振子是电能与机械能的转换器；他们应用逆压电效应把电能转换为动能。简单的压电振子振幅非常小，主要受到压电材料的变形限制。压电电机是机械电驱动系统，并将这种振动通过摩擦耦合来直接驱动转子或滑块的旋转。 压电电机的研究大概始于1942年。在那年，美国学者L.W. Williams and Walter J. Brown建造第一个超声波电机模型，并且在1948年从美国专利局获得第一个专利。 他们的发明是利用压电现象把一个多阶段的电信号转变成机械运动的过程。他们使用压电振子产生弯曲振动从而在振动体端部质点形成椭圆旋转运动。图1 L.W Williams 和 Walter J. Brown发明的压电电机1.从那以后，压电电机领域有了很大的发展。人们根据它们的工作原理或者振动类型来进行分类。图2显示的是从一种实用的观点中选择的基于这些可能性的分类。 我们首先做出非谐振驱动电机和我们集中关注的谐振驱动超声波电机之间的区别。 图2 为压电电机的分类图7所示的 Konica Minolta公司的微型压电电机的工作原理就是惯性原理。一根小的金属轴与压电振动器想连接，运动部分紧贴在其上。当压电片随着较低的加速/减速进行扩张和收缩时，运动部件在摩擦力的作用下运动。而在较高的加速/减速状态时，运动部件因为惯性而发生滑动。 来自NEW FOCUS公司10多年前发明的压电电机具有相同的工作原理。这种压电电机通过装在压板上的压电片直接引起轴的旋转运动。 图7 Konica Minolta的压电电机6图8 来自NEW FOCUS股份有限公司的压电电机7超声电机超声电机是一种通过压电振动器的逆压电效应把电能转化为具有超声频域内的机械振动，从而使运动部件利用摩擦耦合获得连续运动。使用较低的驱动电压能够增加振动器的振幅。超声电机的工作频率在20 kHz到10MHz的范围内。振动器的振幅在20到200纳米的范围内。 在超声电机里，振动器的高频是通过激励不同的振动方式（声音的波）而获得。根据设计要求确定振动器的型号。摩擦材料对于超声波电机的设计也很重要。谐振器不同的谐振模态，方式和摩擦接触的设计导致超声波电机的结构设计会有差异。 超声电机可分成驻波电机和行波电机两类。 在行波电机中，多个驻波的叠加就构成一个行波。活动面上的点在规定的轨道上作椭圆运动。这类行波只能以统一体存在。圆形的谐振器就是行波的连接统一体。行波类压电电机通常以环形和圆盘式设计为主。行波压电电机最著名的设计是圆盘式和环行。驻波电机的工作原理是脉冲理论。转子的运动可通过一系列的微小脉冲来表示。一个微小的脉冲就代表转子上相对应的点的运动。驻波电机能进一步分成单模态和双模态电机。 另外，超声波电机可分成单向和双向电机。在1965年，V. V. Lavrinenko发明了第一台压电超声电机8。这种超声电机是圆盘式压电片挤压光滑的转子组成。在此之前，作为苏维埃社会主义共和国联盟，乌克兰基辅理工学院的候选人，在对有压电转换器的研究中，他已经对压电水晶的旋转进行过观察研究。他在先前的观察研究的基础上发明了第一台超声电机，并在1965年获得苏联电动机的专利8。 图9 V. V. Lavrinenko研究的超声波电机8单向电动机 那项发明8标志着在苏维埃社会主义共和国联盟的超声波电机领域里系统调查和基础研究的开始。在基辅理工学院的科研小组开始阐述基本原理和设计参数，在当时来说完全是一种新型的电机械能转换装置：超声电机，对这台电动机的进一步研究证实了超声电机的基本设计原理的正确性，并在1975年获得了美国压电机结构的专利9及其相近的附加专利10。 图10所示是一台带有环状压电振荡器的超声电机，这个环状压电片受到纵向的激励。振荡器的前沿通过弹簧挤压转子，转子通过一系列的微运动进行运动。图10超声波电机的一种最简单的设计，1975年 在70年代，超声波电机的发展也包括单向的片型电动机。单一片状超声波电机有环状和圆柱状振动模式。金属薄片紧贴在振荡器上，把谐振器的振子转换为转子的旋转运动。薄片产生弯曲的波通过谐振器激励薄片产生椭圆运动。图11 有附上薄片的振动器 1974年11图12展示的是1982年松下公司生产的一台“Elektronika 552-Video”录象机11。 图12 1982年生产的“Elektronika 552-Video”摄相头就是应用超声波电机驱动摄相头的例子 双向电机 很多旋转设置只能朝一个方向作线的运动，双向运动就应运而生了。这种双向运动可通过两个独立的振动器激励相位差来获得或者通过一个独立的振动器产生交叉的两个波获得。线性超声电机是一种很少出差错的驻波电机。利用振荡器激励驻波从而产生运动。激荡器由几个混合的振荡器组成，也可是一个独立的振荡器。像前面提到的那样，引起滑板椭圆运动的是超声电机产生的非平行的几个波的叠加。最简单的或许是一台单独控制的振荡器。 如图13所示是1980年一款最简单的设计。两过振荡器通过一个薄片产生的椭圆运动带动滑板运动12。 http:/www.physikinstrumente.de/products/section7/piezo_motor_index.htm http:/ 图13 超声波电机的最简单原理图14是Uchino教授开发了一种非常有趣的带有两个压电振动器的旋转电机13, 14, 15。图14 使用了圆筒式的压电电机如图所示，圆盘式的压电片挤压在金属汽缸的表面。在汽缸里，通过相位差来激励金属片的像呼啦圈一样的摇摆运动。这种设计具有结构小和生产成本低的特点。 来自新规模技术股份有限公司的特色电机就是利用这个原理。 有圆筒形定子的超声波电机 压电的圆筒型转子的一个变量使用一种交换方式和真实的长度方式。两种方式的重叠这根管的末端上的点进行椭圆的轨道运动。这运动能用来推挤末端表面的一个转子转动。 图22为电机上的不同变量的振动器25. 图22 为超声波电机圆筒状的转子，1980 图23显示的是一台基于弯曲波激励产生的旋转驻波的超声电机26。超声电机的转子是由压电环和固定的金属振动器以及推进器组成。 决定运动方向是特性弯曲波的激励。推进机向前作倾斜的线的运动，因此驱动挤压在推进器上的转子运动。这种超声波电机被Seiko应用在怀表上。 图24是Physik Instrumente(PI)用圆柱体的振动器设计开发的单向旋转电机27，该电机利用切线轴向的振动方式。图片也显示了计算机模拟的电动机的工作原理。 图23 (a) 电动机结构 (b) 电极和磨擦位子 (c) 驻波和转子方向 图24 来自Physik Instrumente(PI)的使用切线轴向驻波圆筒形振动器的单向电机的设计和工作原理行波电机 在1982年T. Sashida发明一台基于行波的超声电机28。在这台电动机里，在摩擦表面上的点的椭圆运动是由两个驻波合成一个行波引起的。图25是Shinsei Corporation公司根据设计做出的一款行波电机。 图26所示是用合成振动器的超声波电机29,30.在这些电动机里，压电的磁盘励磁机压在金属谐振器之间。电动机使用弯曲方式。图25 来自Shinsei Corporation公司1983年的行波超声电机的图片和它的工作原理 图26 有合成振动器的电动机变量 图27表明了来自Physik Instrumente (PI)设计的应用圆筒状的压电块产生纵向行波的3个相位的电机及其工作原理31。图27使用纵向行波设计的电动机，1995这些电动机的振动器由3个纵向的驻波叠加组成一个纵向的行波来激励。图28来自Physik Instrumente(PI)的使用纵向行波设计的3个相位的电动机。图28 Physik Instrumente(PI)的微型行波电机结论超声电机续他们之后已经有一段历史。很多不同类型的电机和工作原理已经发展起来，也将不断改进，并且取得专利权。这里阐述的基本原理是一种不完全的表达。他们有一个共同的基本原理：通过一些方式激励压电材料来获得点的运动。运动的幅度比较小，但是运动的频率较高，移动部分最多能达到1m/s的速度。超声电机在一些特殊的场合的使用远远胜过传统的电磁电动机的特性(例如没有磁场产生，低速大转矩，定位精度高)。 不过，超声电机在自动化和微型化领域内应用的最广，在那些领域内可接受该类电动机的效率和廉价性。一个决定性因素是这些电动机可实现大量生产。新发展证明电动机可能非常少部分生产，并且价格成为超声波电机最大的争论。 事实证明超声电机已经完成了一些必要的突破，并且在不久的将来，超声电机在工业中的将站有很重要的地位。 Survey of the Various Operating Principles of Ultrasonic Piezomotors K. Spanner Physik Instrumente GmbH & Co. KG, Karlsruhe, Germany Abstract: Piezoelectric ultrasonic motors have been known for more than 30 years. In recent years especially, a large number of different designs have been developed, both for rotation and linear drives. This talk will provide a definition of piezoelectric ultrasonic motors and classify their different operating principles. The operation of each type will then be explained, commercially available implementations described and the advantages and disadvantages of each discussed. The goal is to provide an international perspective on the current state of development of piezoelectric ultrasonic motors. Keywords: piezomotor, PZT, ultrasonic motor, travelling-wave, standing-wave, piezoelectric actuator Introduction There is today a large variety of drive designs exploiting motion obtainable from the inverse piezoelectric effect. Ultrasonic piezomotors have a very special place among such devices. These motors achieve high speeds and drive forces, while still permitting the moving part to be positioned with very high accuracy. Such characteristics make these motors of great interest for many companies who make precision devices for which these drives are, in many cases, irreplaceable. Piezoelectric Motors Piezoelectric actuators are electro-mechanical energy transducers; they transform electrical energy into motion using the inverse piezoelectric effect. The travel range of a simple piezo actuator is very small, being limited by the maximum possible deformation of the piezoceramic material. Piezoelectric motors are electro-mechanical drive systems in which the limited displacement of a piezoceramic element is converted into the unlimited rotary or translatory motion of a rotor or slider. The displacement of the piezoceramic in the desired direction of motion is transferred to the rotor or slider over an intermittent frictional coupling. The story of the piezomotor began, presumably, in 1942. In that year, Alfred L.W. Williams und Walter J. Brown of Brush Development Company reported having built a “Piezoelectric Motor,” for which they received the first patent from the US Patent Office in 1948. Their invention comprised a process for converting a multi-phase electrical signal into mechanical motion using the piezoelectric phenomenon. They used different types of piezoelectric bending actuators, so arranged that their vibrational motion was converted into rotary motion of a shaft and gear. Fig. 1 Piezoelectric motor of L.W Williams and Walter J. Brown 1. Since then, there have been numerous developments in the field of piezoelectric motors. They can be classified by working principle, geometry, or the type of oscillation excited in the piezoceramic. Fig. 2 shows a classification based on a mix of these possibilities, chosen from a pragmatic point of view. We make first an overall distinction between quasi-static motors and the ultrasonic motors on which we wish to concentrate our attention here. Fig. 2 Classification of piezomotors http:/www.physikinstrumente.de/products/section7/piezo_motor_index.htm http:/www.physikinstrumente.de/products/section7/piezo_motor_index.htm 2006 PI (Physik Instrumente) http:/www.pi.ws Phone +49 (721) 4846 - 0 Fax 4846 - 499 White Paper for ACTUATOR 2006Quasi-static Piezomotors The quasi-static piezomotors operate on either the clamping principle or the inertial principle. In clamping-type motors, the rotor or slider is passed “hand-over-hand” between two sets of clamping and driving actuators. At any point in time, the set of actuators that is moving in the drive direction is the set that is clamped to the slider or rotor, while the other set is unclamped and moving “backwards,” preparatory to “taking a new bite.” In inertial-type motors, inertia and the difference between the static and dynamic friction coefficients is used (the frictional force on the slider is reduced when slippage generated by the sliders inertia occurs). During the slower displacement of the actuator in the drive direction, the slider follows the actuator with no slippage. In the next phase, the actuator moves in the opposite direction so rapidly that the slider, unable to follow due to its inertia, lets the actuator slip back beneath it. What these motors have in common, is that they operate well below the resonant frequency of their piezoceramic actuators. Clamping-type Motors The first design for a clamping-type piezomotor was the Inchworm motor proposed by Burleigh Instruments, Inc. in 1974. 2. Fig. 3 shows how the Inchworm motor works. Fig. 3 Working principle of the Inchworm Motor 2, 1974 The desired motion is obtained by the sequenced activation of three piezoelectric actuators. The two outer actuators (Numbers 1 and 3) can clamp the slider and can be activated independently of one another. The central actuator (Number 2) is used to change the distance between the two outer actuators and thus to drive the slider. Fig. 4 shows the design of the quasi-static Piezo Walk Drive, another system operating in the quasi-static mode. Fig. 4Piezo Walk Drive 3, 1993 The Piezo Walk Drive has two legs and four actuators. Two of the actuators are responsible for the (forward or backward) drive motion, and two for (alternately) engaging and disengaging the legs. As with a person walking, continuous forward or backward motion is possible. The two legs are parallel to each other and are pressed against the runner via levers. Each drive piezo can move the runner forwards or backwards by about 15m. As one drive piezo approaches the end of its travel, the other clamp piezo will engage the other leg so that its drive piezo can take over. There is always at least one leg engaged with the runner, and manufacturing tolerances are fully compensated. Fig. 5 shows a piezo drive for precision engineering or optical devices. 4. Fig. 5 Piezoelectric motor 4, 1994 This drive consists of a number of drive elements pressed against a slider. Each drive element is a piezo bimorph. The plates in the bimorph are electrically isolated and can be controlled independently. Exploiting the differential expansion or contraction of the bonded plates in the bimorph, the free end can be made to follow a trajectory with components in the lengthwise and bending directions as shown. If the two plates are excited with sine wave signals 90 out of phase, the free end will trace an elliptical pattern and drive the slider. http:/www.physikinstrumente.de/products/section7/piezo_motor_index.htm http:/www.physikinstrumente.de/products/section7/piezo_motor_index.htm 2006 PI (Physik Instrumente) http:/www.pi.ws Phone +49 (721) 4846 - 0 Fax 4846 - 499White Paper for ACTUATOR 2006The polarity of the phase difference will determine the direction of motion of the slider. Fig. 6 shows a piezoelectric stepper motor from the Swedish company PiezoMotor Uppsala AB. 5. Both the drive unit and the working principle are the same as in 4 Fig. 6 Piezoelectric motor from PiezoMotor Uppsala AB 5 Inertial Principle The miniature piezomotor from Konica Minolta shown in Fig 7 works using the inertial principle. A thin metal shaft is attached to the piezo actuator, and the moving part is clamped to it. When the piezo expands or contracts with low acceleration/deceleration, the moving part moves with it, held by friction. At higher accelerations/decelerations, the inertia of the moving part prevents it from following and it slides. Fig. 7 Konica Minolta piezomotor 6 The piezomotors from New Focus, which appeared more than ten years ago, work on the same principle. In them, the piezoelectric element acts directly on the clamp holding the shaft, causing the shaft to rotate. Fig. 8 Piezomotor from New Focus Inc.7 Ultrasonic Piezomotors An ultrasonic piezomotor is one in which electrical energy is converted by the inverse piezo-effect to obtain oscillation of the piezo actuator at one of its resonant frequencies in the ultrasonic range, and this oscillation used in conjunction with a smooth frictional contact to obtain unlimited motion of the moving part. The increase in oscillation amplitude of the actuator due to resonance means that a lower drive voltage can be used. The working frequencies of ultrasonic motors range from 20 kHz to 10 MHz. The amplitude of the actuator motion is in the range of 20 to 200 nm. In ultrasonic motors, the oscillations of the actuator result from excitation of different vibration modes (acoustic waves) in the actuator shape. The desired modes determine the shape and proportions of the actuator. The design of the ultrasonic motor is also dependent on that of the frictional components. The large number of different eigenmodes of a resonator, the combinations of different vibration modes and the design of the frictional contact lead to a large number of different possible ultrasonic motor designs. Ultrasonic piezomotors can be divided into two groups, standing-wave motors and traveling-wave motors. In traveling-wave motors, the superposition of multiple standing waves creates a traveling wave. Points on the active surface of the stator trace elliptical trajectories. Such traveling waves can only exist along an unbounded continuum. Resonators with circular geometry offer such a continuum for traveling waves. Traveling-wave piezomotors therefore usually have a stator in the form of a disk, ring or hollow cylinder. The best-known designs for traveling-wave piezomotors employ either a circular bending wave or a pseudo-longitudinal wave. Standing-wave motors operate on the principle of mico-impulses. The motion is transferred to the rotor as the summation of a series of microscopic pushes or impulses. The micro-impulses are directed at an angle to the surface of the rotor. Standing-wave motors can further be divided into single-mode and bimodal motors. In addition, ultrasonic motor designs can be classified as unidirectional or bidirectional. http:/www.physikinstrumente.de/products/section7/piezo_motor_index.htm 2006 PI (Physik Instrumente) http:/www.pi.ws Phone +49 (721) 4846 - 0 Fax 4846 - 499 White Paper for ACTUATOR 2006The first piezoelectric ultrasonic motor was introduced by V. V. Lavrinenko in 1965 8. It consisted of an ultrasonic piezoelectric plate pressed against a smooth rotor. The year before, as candidate at the Polytechnic Institute in Kiev, Ukraine, USSR, he had observed rotation of piezoceramic crystals in their holders in the course of research with piezoelectric transducers. This observation led to the construction of the first ultrasonic piezomotor, which was registered by the issuance of a Soviet patent for a type of “Electric Motor in 1965 8. The ultrasonic motors developed in the 70s also included unidirectional lamina motors. The mono-mode lamina ultrasonic motor uses the radial vibration mode of a piezoceramic cylinder or ring. Metallic laminae, or vanes, are attached to the oscillator; they convert the radial oscillation of the resonator to a rotary motion of the rotor. A bending wave is created in the laminae, which, in combination with the radial oscillation of the resonator, excites elliptical motion of the lamina tips. Fig. 11 Actuator with attached laminae 197411 Fig. 12 shows a photo of a factory-built video recorder, the Electronika 552 Video, manufactured by the Positron company in 1982. Fig. 9: V. Lavrinenkos ultrasonic piezomotor 8 Unidirectional Motors That invention 8 marked the beginning of systematic investigation and basic research in the area of ultrasonic piezomotors in the USSR. The research group at the Kiev Polytechnic Institute began working out the basic principles and design parameters of what was at that time a completely new type of electro-mechanical energy conversion device: the ultrasonic piezomotor. Further work on this motor led to recognition of fundamental design principles for ultrasonic motors, which were detailed in 1975 in a US Patent on “Piezoelectric Motor Structures” 9 and in similar additional patents 10. Fig. 12 Example of the “Elektronika 552-Video” a factory-built video recorder with an ultrasonic motor to power the drive axis, 1982 Bidirectional Motors While many rotary applications need to move only in one direction, for linear motion, bidirectional drives are required. This can be obtained either using two separate actuators excited with a phase difference, or by superimposing two oscillations in a single resonator. Linear ultrasonic motors are, with very few exceptions, standing-wave motors. They produce their motion using a standing wave excited in the stator. The stator is either of a hybrid construction consisting of several actuators, or employs a single actuator. Fig. 10. shows an ultrasonic motor with a piezoceramic plate as oscillator (stator). The piezoelectric plate is excited in the longitudinal mode. The front edge of the oscillator is pressed against the rotor with a spring. Motion is imparted to the rotor by a series of micro-impulses. As already mentioned, elliptical motion for driving a slider can be generated in an ultrasonic motor by the superposition of two non-parallel, out-of-phase oscillations. Simplest is perhaps to use separate actuators, which can also be separately controlled. This simplest design is shown in a layout from 1980 in Fig. 13 The connecting piece joining the two actuators traces an ellipse and imparts motion to the slider across a frictional interface 12. Fig. 10 Simplest design for an ultrasonic piezomotor 1975 http:/www.physikinstrumente.de/products/section7/piezo_motor_index.htm 2006 PI (Physik Instrumente) http:/www.pi.ws Phone +49 (721) 4846 - 0 Fax 4846 - 499 2006 PI (Physik Instrumente) http:/www.pi.ws Phone +49 (721) 4846 - 0 Fax 4846 - 499 2006 PI (Physik Instrumente) http:/www.pi.ws Phone +49 (721) 4846 - 0 Fax 4846 - 499 White Paper for ACTUATOR 2006A longitudinal or bending mode (L1B2) of this actuator is excited, permitting the motor to change direction. Another L1B2 ultrasonic motor design, shown in Fig. 16, is that of Prof. R. Bansiavichus 18. In it, the piezoelectric plate actuator is excited in a longitudinal and a bending mode simultaneously. The direction change of this motor is effectuated by switching the diagonally arranged electrodes. Fig. 13 Simple principle for an ultrasonic Motor A very interesting design for a rotary motor with two piezoactuators was developed by Prof. Uchino (Fig. 14) 13,14,15. Fig. 16 Prof. Bansiavichus ultrasonic motor, 1977 Fig. 17 shows an L1B2 ultrasonic motor from Nanomotion Ltd. 19. This motor has an ultrasonic actuator similar to that of Prof. Bansiavichus motor, with the exception that the pusher is located on the end of the piezoelectric plate. Fig. 14Piezomotor using bending mode of a hollow cylinder Piezoelectric plates are pressed against the surface of the metal cylinder as shown. They are then excited with a phase difference, exciting a wobbling motion in the cylinder, like the wobble of a hula hoop. This design is characterized by its compactness and low manufacturing costs. The SQUIGGLE Motor from New Scale Technologies, Inc. operates on this principle. Fig. 17 Schematic representation of an ultrasonic motor 1994 Fig. 18 shows the design of a 2-phase linear motor from Physik Instrumente (PI), its piezoelectric actuator plate lying lengthwise with two attached friction tips 20. Micro-Impulse Drives with Piezoceramic Plate Actuators Fig. 15 shows an ultrasonic motor with diagonally arranged electrodes on the main face of the plate-shaped actuator. 17. Fig. 15 Motor with diagonally arranged electrodes on a plate-shaped actuator 1976 Fig. 18 Two-phase motor from Physik Instrumente (PI) based on longitudinal and bending standing waves in the actuator plate, 1999 http:/www.physikinstrumente.de/products/section7/piezo_motor_index.htm 2006 PI (Physik Instrumente) http:/www.pi.ws Phone +49 (721) 4846 - 0 Fax 4846 - 499White Paper for ACTUATOR 2006Another variation uses a tortional mode and a true longitudinal mode in a piezoelectric cylindrical stator. The superposition of the two modes imparts elliptical trajectories to points on the ends of the tube. This motion can be used to turn a rotor pressed against the end face. This motor operates on the basis of simultaneous electrical excitation of longitudinal and bending standing waves in the actuator. Fig. 19 shows a 2-phase ultrasonic linear motor from Physik Instrumente (PI) in which the actuator is excited with two longitudinal standing waves; one of the waves covers the actuator in the lengthwise direction while the other spreads out in the height direction 21. Fig. 22 shows different variations on actuators for such motors 25. Fig. 22 Cylindrical stators for ultrasonic motors, 1980. Fig. 23 shows a rotating-standing-wave ultrasonic motor based on excitation of a bending wave. 26. The stator of the ultrasonic motor consists of a piezoceramic ring, a bonded metallic resonator and pushers attached to the resonator. A bending wave with characteristics depending on the desired direction of motion is excited. The pushers move along inclined, linear trajectories, and thus drive the rotor, which is pressed against them. This ultrasonic motor design has been used by Seiko for a pocket watch. Fig. 19 Two-phase motor from Physik Instrumente (PI) with two longitudinal standing waves in the actuator plate, 2001 Fig. 20 shows the simplest of the well-known ultrasonic motors 22,23developed by Physik Instrumente (PI). The actuator of this motor has a common drain electrode and two excitation electrodes. This motor operates on the basis of the (1,3) excitation of an asymmetric standing wave in the actuator. Fig. 20 Single-phase motor from Physik Instrumente (PI) with an asymmetric standing wave in the actuator plate, 2004 Fig. 21 shows a new ultrasonic micromotor from PI. 24. Fig. 23 a) Motor structure b)Electrode and friction tip locations c)Standing wave and rotor direction Fig. 21 CAD design of the newly developed ultrasonic piezoelectric micromotor Fig. 24 shows the design of a single-phase rotational motor developed by Physik Instrumente (PI) with a cylindrical actuator 27 employing the tangential-axial vibration modes. The figure also shows a Ultrasonic Motors with Cylindrical Stator http:/www.physikinstrumente.de/products/section7/piezo_motor_index.htm 2006 PI (Physik Instrumente) http:/www.pi.ws Phone +49 (721) 4846 - 0 Fax 4846 - 499 White Paper for ACTUATOR 2006computer simulation which elucidates the working principle of the motor. Fig. 24 Design and working principle of a single-phase motor from Physik Instrumente (PI) with cylindrical actuator using tangential-axial standing waves 2004 Traveling Wave Motors In 1982 T. Sashida invented an ultrasonic motor based on the use of traveling waves 28. In this motor, the elliptical trajectories of the points on the friction surface result from a traveling bending wave formed from two standing bending waves. Fig. 25 illustrates the design such a traveling-wave motor, made by the Shinsei Corporation. Fig. 25 Photograph and working principle of an ultrasonic motor using traveling bending wave, from the Shinsei Corporation, 1983 Fig. 26 shows an ultrasonic motor with composite actuators 29,30. In these motors, piezoelectric disk exciters are pressed between metallic resonators. The motor uses the bending mode. 1989 1991 Fig. 26 Motor variations with composite actuators The drawings in Fig. 27 illustrate the working principle and the design of a 3-phase motor from Physik Instrumente (PI) using longitudinal traveling waves on the circumference of a piezoceramic hollow cylinder. 31. Fig. 27 Motor design using longitudinal traveling waves, 1995 The actuators of these motors are excited with longitudinal traveling waves consisting of the superposition of three longitudinal standing waves. Fig. 28 shows prototypes of 3-phase motors from Physik Instrumente (PI) using longitudinal traveling waves. 19942000 Fig. 28 Prototypes of miniature traveling wave motors from Physik Instrumente (PI) Conclusions Ultrasonic motors already have a long development history behind them. Many different implementations and working principles have been developed, will be improved, and patented. The basic principles shown here are only an incomplete selection. They all have one basic principle in common: A piezoelectric element is excited in an eigenmode in such a way that at an extraction point, a particular motion component is obtained. The motion amplitudes are small, but given the high frequency, the moving part can achieve speeds of up to 1 m/s. http:/www.physikinstrumente.de/products/section7/piezo_motor_index.htm 2006 PI (Physik Instrumente) http:/www.pi.ws Phone +49 (721) 4846 - 0 Fax 4846 - 499White Paper for ACTUATOR 2006Piezoelectric ultrasonic motors have characteristics which make them far superior to conventional electromagnetic motors in certain market segments (for example, non-magnetic versions, high power-down holding forces, high positioning accuracy). The greatest potential, however, will be in the area of automation and miniaturization, where compact and inexpensive motors with acceptable efficiency are required. The deciding factor is the price at which these motors can be produced in large quantities. The new developments demonstrate that motors can be built from very few parts, and that price can thereby become an argument for USMs. It can be assumed that USM development has achieved the necessary breakthroughs, and that USMs will be of increasing importance in industrial products in the ne
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