Traveling-wave piezoelectric linear motor Part I: the stator design.

A new type of piezoelectric linear motor incorporating a traveling wave has been developed. The linear motor is comprised of a stator and a carriage. The stator design, which consists of a meander-line structure and gear teeth mounted on the meander-line structure, is the focus of this article. The meander-line structure is constructed with bimorph actuators arranged in a line. These actuators are driven by two phased sets of alternating current (ac) in order to generate a traveling wave. The traveling wave is transferred to the gear teeth, by which the carriage is driven. Modeling of the stator is derived by use of a strain energy method. The performance of various materials is evaluated by analytical and experimental methods. The analytical and the experimental results are quite approximate. Modal analysis is investigated using ANSYS. Appropriate modes associated with ultrasonic levels of resonant frequency are selected to obtain desired motion and to enhance the output performance. Surface speed for various applied input voltage are studied and indicate a nearly linear relationship. The stator in combination with the carriage makes up the linear motor.     

Traveling-wave piezoelectric linear motor part II: experiment and performance evaluation

This article continues the discussion of a traveling-wave piezoelectric linear motor. Part I of this article dealt with the design and analysis of the stator of a traveling-wave piezoelectric linear motor. In this part, the discussion focuses on the structure and modeling of the contact layer and the carriage. In addition, the performance analysis and evaluation of the linear motor also are dealt with in this study. The traveling wave is created by stator, which is constructed by a series of bimorph actuators arranged in a line and connected to form a meander-line structure. Analytical and experimental results of the performance are presented and shown to be almost in agreement. Power losses due to friction and transmission are studied and found to be significant. Compared with other types of linear motors, the motor in this study is capable of supporting heavier loads and provides a larger thrust force.     

Design and performance testing of an ultrasonic linear motor with dual piezoelectric actuators

In this work, design and performance testing of an ultrasonic linear motor with dual piezoelectric actuator patches are studied. The motor system consists of a linear stator, a pre-load weight, and two piezoelectric actuator patches. The piezoelectric actuators are bonded with the linear elastic stator at specific locations. The stator generates propagating waves when the piezoelectric actuators are subjected to harmonic excitations. Vibration characteristics of the linear stator are analyzed and compared with finite element and experimental results. The analytical, finite element, and experimental results show agreement. In the experiments, performance of the ultrasonic linear motor is tested. Relationships between velocity and pre-load weight, velocity and applied voltage, driving force and applied voltage, and velocity and driving force are reported. The design of the dual piezoelectric actuators yields a simpler structure with a smaller number of actuators and lower stator stiffness compared with a conventional design of an ultrasonic linear motor with fully laminated piezoelectric actuators.     

Stator design of a new type of spherical piezoelectric motor

The stator design of a new type of spherical motor driven by piezoelectric actuators is developed. A curved piezoelectric actuator is designed to attach to the spherical surface. A series of the curved piezoelectric actuators is laid in a line around a spherical surface. By applying an appropriate voltage signal with phase difference on neighboring actuators, a traveling wave is generated on the hemispherical shell. Each set of curved piezoelectric actuators is designed to provide motion with a single degree-of-freedom (DOF). With two or three sets of the piezoelectric actuators constructed to be mutually perpendicular, the motor can provide 2-DOF or 3-DOF motion. Stator design and analysis and experiment for the 1-, 2-, and 3-DOF conditions are presented in this article. Analytical calculation and experiment results of several fundamental characteristics of the stator are in good agreement. Performance evaluation of rotation speed and torque of the stator and some implementation problems are also addressed.     

二自由度行波型超声波电机定子的数学模型与实验研究

二自由度行波型超声波电机是一种新型多自由度超声波电机。本文从二自由度行波型超声波电机的驱动机理和基本结构出发,就电机的结构实现、驱动球转子的最佳定子结构进行了分析,利用所建立的有限元模型进行定子振动的模态分析和共振频率计算,提出了外缘大倾角内缘线接触的行波定子。然后建立定子的接触模型,对其机械性能进行分析。测试结果表明,修正的数学模型更加符合电机的实际运行特性。所研制样机的球转子直径为45mm,定子直径为30mm,实现的堵转力矩为120mNm,空转转速12r/min。本文工作为多自由度行波型超声波电机的优化设计、性能提高奠定了基础。     

旋转型行波超声电机定子的子结构模型研究

按照旋转型行波超声电机定子的结构特点将其划分为几个较简单的子结构,分别对其进行了动态特性分析,最后在子结构模态综合法的基础上建立了整个定子的分析模型。该模型可以很方便地计算电机定子的各阶模态,并且由于运用Guyan静力法将定子齿单元的刚度和质量凝聚到基体之上,不仅恰当地描述了齿对定子动态特性的影响,而且达到了缩减计算量的目的。通过算例和实验说明此理论模型是可行的,可用于电机系统性能预测和参数优化设计。     

A piezoelectric motor using flexural vibration of a thin piezoelectric membrane

This paper describes a new implementation of a disk-type piezoelectric motor, whose stator is a commercial available piezomembrane composed of a nickel alloy disk to which a piezoceramic disk is bonded. The two disks are concentric, and the total thickness is very small. Ultrasonic motors are based on the concept of driving a rotor by mechanical vibration excited on a stator, via the piezoelectric effect. The rotor is in contact with the stator, and the driving force is the frictional force between rotor and stator. To transform the mechanical vibration of the stator in the rotor rotation, a traveling wave must be excited on the stator surface. The proposed motor can be regarded as a disk-type, single wavelength motor in which the traveling wave is due to the natural flexural vibration of the piezomembrane at low frequency. The behavior of the stator is analyzed both theoretically, by using the theory of isotropic and homogeneous vibrating plates, and by means of a commercial finite element computer code, finding a good agreement with the experimental results. The main features of the motor are very small thickness, appreciable torque, and high speed, obtained with low input power at low voltage; the intended application is to substitute the moving-coil in analogic instrumentation.     

杆式行波超声电机运动机理的研究

本介绍了作发展的一种杆式行波超声电机的结构。基于振动和波动理论，深人研究了杆式行波超声电机的运行机理，推导了定子端面上任意质点运动轨迹，证明了在一定的激励条件下，定子端面沿Z向、径向和周向都可形成行波。描述了定子端面某些点的运动轨迹的空间分布。还提出了定、转子问最佳接触角和有效椭圆的概念。这些都为设计高效率的杆式超声电机提供了理论依据。     

纵振换能器式圆筒型超声电机振动特性的研究

以纵振夹心换能器式圆筒型超声电机为研究对象,对换能器的振动状态进行了分析,给出了换能器弯曲振动的产生原因;研究了耦生弯振对电机机电耦合系数以及圆筒中弯振行波质量所带来的影响,耦生弯振的存在使得定子模态特征频率偏离换能器谐振频率,并使得定子圆筒中的弯振行波产生了畸变。最后,提出一种采用换能器弯振激励圆筒径向弯振的模态组合方式。     

Modeling of a piezoelectric rotary ultrasonic motor

A piezoelectric rotary ultrasonic motor is modeled for the purpose of predicting, a priori, motor performance as a function of design parameters. The Rayleigh-Ritz assumed mode energy method is used to model the distributed piezoceramics and the traveling wave dynamics of the stator. Natural frequencies and modeshapes are obtained for a generally configured motor. Nonlinear normal and tangential interface forces between the rotor and stator are incorporated into the forcing function along with the linear piezoelectric forcing. Given the applied torque, applied axial loading, and piezo drive voltages as inputs to the model, general motor performance measures are obtained-namely speed, input power, output power, and efficiency. The approach presented here provides a general framework for modeling these motors as well as a design tool for optimizing prototypes with the added flexibility of allowing for a wide variety of geometries and materials     

电机定子铁芯振动特性分析的一种解析方法

随着新能源汽车的发展,用户对电机噪声的要求日趋严格,噪声振动分析已经成为电机开发中的重要内容。定子的电磁振动是电机的主要噪声源,由于电机定子的复杂结构,目前常用有限元方法建模分析定子铁芯的振动特性,耗时太长,不能满足定子优化设计的振动噪声特性快速计算要求。提出了一种解析方法用于计算定子铁芯的振动特性。采用厚壳-梁耦合结构对定子铁芯进行简化,计入了定子齿对振动特性的影响;推导了耦合结构的解析能量泛函,并使用Rayleigh-Ritz法计算出定子铁芯的固有频率和模态振型。应用该解析方法计算了电机定子振动特性,分析了定子齿枢的影响,并与商用软件的有限元建模分析结果进行比较,两者误差小于5%,验证了该解析方法的准确性。     

A high-power traveling wave ultrasonic motor

In the present work, a traveling wave ultrasonic motor (TWUSM) is proposed. It is composed of an annular-shaped stator and two cone-shaped rotors that are pressed in contact to the borders of the inner surface of the stator. A rotating traveling wave has been generated in the stator by using as vibration generators two bolted Langevin transducers (BLT) opportunely shifted in space and in time. The vibrational behavior of the stator as well as the traveling wave generation has been simulated with the finite-element method (FEM) software. A prototype of the motor has been manufactured and experimentally characterized. It exhibits a static torque of about 0.8 N x m and a maximum angular speed of about 300 rpm. Possible variations of the present design aimed to increase output torque or minimize encumbrance are described and discussed.     

新型箝位式压电电机的设计研究

针对传统箝位式压电电机在谐振态下工作时,方波振动的箝位部分结构设计复杂问题,提出一种新型箝位式压电电机。该电机箝位部分与驱动部分均由同频正弦电压驱动实现正弦振动,通过定子对动子的箝位接触,实现动子单向输出运动。相较于传统箝位式压电电机和超声电机,该电机的定子结构设计无需采用模态简并,结构设计难度降低。利用有限元仿真确定定、动子结构参数,制造样机并搭建实验平台。对箝位部分分别采用正弦波与方波做激励,再对驱动部分进行波形对比,表明正弦波亦能达到预期效果。实验结果表明:准静态时,激励电压频率为250Hz、电压峰峰值Vp-p为10V时,步进距离为0.5μm,步进速度0.13mm/s;谐振态时,激励电压频率为540Hz、电压峰峰值Vp-p为70V时,步进距离为32μm,步进速度16.9mm/s;该电机可兼顾低频高分辨率和高频高速输出以实现跨尺度工作。     

A travelling wave rotary motor driven by three pairs of Langevin transducers

In this work, numerical simulations and experimental measurements carried out on a high-power ultrasonic motor are presented. The proposed motor is composed of an annular shaped stator and two cone-shaped rotors. The rotors are pressed into contact with the edges of the inner surface of the stator by means of a pre-stress system. A traveling rotating wave is generated in the stator by three pairs of Langevin transducers suitably shifted both in space and time. Each transducer is designed to excite radial nonaxisymmetric modes in the ring. The motor has been effectively clamped to the housing by using two flanges passing through the middle plane of 2 transducers. Finite element analysis was employed to evaluate two different configurations of the motor, both using 6 driving transducers, and to analyze the effect of the flange on the design and on the performance of the transducer. Experimental measurements carried out on a manufactured prototype show that the proposed motor exhibits greatly improved performance in terms of output torque and mechanical power compared with similar previous prototypes which use fewer driving transducers and a different clamping system. The motor weighed 0.67 kg, and had a working frequency of 23.6 kHz, maximum rotational speed of 116 rpm, and static torque of 0.94 Nm.     

A cylindrical traveling wave ultrasonic motor using a circumferential composite transducer

This paper intends to present and verify a new idea for constructing traveling wave ultrasonic motors that may effectively avoid the drawbacks of conventional traveling wave motors using bonded PZT plates as the exciting elements. In the configuration of the motor's stator, a composite sandwich type transducer is used to excite a traveling wave in a cylinder with two cantilevers as the coupling bridges between the transducer and the cylinder. The design process of the stator is described using the FEM modal analysis method, and the establishment of traveling wave on the cylindrical stator was simulated by FEM transient analysis. To verify the theoretical analysis results, a laser Doppler scanner was employed to test the mode shapes of a prototype stator excited by the longitudinal and bending vibrations respectively. Finally, to validate the design idea, a prototype motor was fabricated and tested; the typical output features are no-load speed of 156 rpm and maximum torque of 0.75 N·m under exciting voltages of 70 V(rms) applied to excite the longitudinal vibration of the transducer and 200 V(rms) applied to excite the bending vibration.     

A standing wave-type noncontact linear ultrasonic motor

In this study, a novel standing wave-type noncontact linear ultrasonic motor is proposed and analyzed. This linear ultrasonic motor uses a properly controlled ultrasonic standing wave to levitate and drive a slider. A prototype of the motor was constructed by using a wedge-shaped aluminum stator, which was placed horizontally and driven by a multilayer PZT vibrator. The levitation and motion of the slider were observed. Assuming that the driving force was generated by the turbulent acoustic streaming in the boundary air layer next to the bottom surface of the slider, a theoretical model was developed. The calculated characteristics of this motor were found to agree quite well with the experimental results. Based on the experimental and theoretical results, guidelines for increasing the displacement and speed of the slider were obtained. It was found that increasing the stator vibration displacement, or decreasing the gradient of the stator vibration velocity and the weight per unit area of the slider, led to an increase of the slider displacement. It was also found that increasing the amplitude and gradient of the stator vibration velocity, or decreasing the weight per unit area of the slider and the driving frequency, gave rise to an increase of the slider speed. There exists an optimum roughness of the bottom surface of the slider at which the slider speed has a maximum     

Rotor Design and Finite Element Analysis of Traveling Wave Rotaty Ultrasonic Motor

The dynamic transfer mechanism of the traveling wave rotary ultrasonic motor rotor-stator' s contact surface is studied in the paper and the key parts stator and cone flexible rotor of ultrasonic motor are designed.The three-dimensional contact model and finite element model considering the radial sliding between the rotor and the stator are established. The relation between the stator surface particle that amplitude frequency characteristics,resonance speed,radial displacement of ultrasonic motor and the tooth height are analyzed. Mass point radial relative displacement of contact surface between the cone flexible rotor,flexible rotor and the stator are contrasted. The cone flexible rotor is better placed on the surface of the stator tooth through its elastic deformation is interpreted. The cone flexible rotor reduces the radial slip between the stator and the output efficiency of ultrasonic motor is improved. The displacement trajectory of the stator surface is synthesized in a row wave cycle. The method of the stator mass point elliptical motion drives the rotor rotation is verified.     

Driving mechanism, design, fabrication process, and experiments of a cylindrical ultrasonic linear microactuator

A new type of cylindrical ultrasonic linear microactuator (CULMA) is introduced. The traveling wave generation condition in the stator is presented, which was confirmed using simulation and experimentation. The design and fabrication process to develop the stator is described. The stator was successfully fabricated using metallic glass and a sputtering method, and the vibration of the prototype matched the simulation results. When the driving frequency is at 626 kHz, the traveling wave in the stator was observed. Loaded with a pipe slider, the slider movement was experimentally demonstrated and the motion measured with 26 mm/s in peak speed. This paper presents a traveling wave generation method in a CULMA which would also available in other microactuators or MEMS-scale ones.     

车用永磁同步电机电磁噪声分析研究

以电动汽车驱动用永磁同步电机为研究对象,从作用于电机定子表面的电磁力波和电机定子结构的动态特性两个方面对电动汽车驱动用永磁同步电机空载工况的电磁噪声展开研究.通过研究永磁同步电机产生电磁力波的机理,推导了空载工况电磁力波的解析分析方法,结合电磁仿真的手段,精确计算了电机在空载工况下电磁力波的波次、频率和幅值;通过建立电机定子结构的有限元仿真模型及有限元模态仿真计算,得到了定子结构的模态频率和振型.发现：电机定子结构的前6阶模态频率较低,电机空载工况在调速过程中所激发的电磁力容易引起电机定子结构的共振.该研究为电动汽车驱动用永磁同步电机的减振降噪提供了指导.     

超声电机定子热机电耦合特性

应用于极端环境的超声电机会受到温度场、应力场和电场的共同作用,定子在热机电耦合激励下的响应与电机工作特性密切相关.以行波型旋转超声电机为对象建立定子的能量泛函,采用假设模态的方法得到了热机电耦合动力学模型.运用有限元方法对热机电耦合作用下的定子进行仿真,分析了与理论计算结果的差异.建立了定子热扫频试验平台和热变形试验平台,测定温度对定子稳态形变、模态频率和振幅的影响,对理论模型的分析方法进行了评价.理论分析和试验结果揭示了超声电机定子在热机电耦合作用下的振动行为的变化规律,为下一步极端环境超声电机的设计和优化提供了依据.