Performance evaluation of traveling wave ultrasonic motor based on a model with visco-elastic friction layer on stator

A new visco-elastic contact model of traveling wave ultrasonic motor (TWUSM) is proposed. In this model, the rotor is assumed to be rigid body and the friction material on stator teeth surface to be visco-elastic body. Both load characteristics of TWUSM, such as rotation speed, torque and efficiency, and effects of interface parameters between stator and rotor on output characteristic of TWUSM can be calculated and simulated numerically by using MATLAB method based on this model. This model is compared with that one of compliant slider and rigid stator. The results show that this model can obtain bigger stall torque. The simulated results are compared with test results, and found that their load characteristics have good agreement.     

基于电接触法的行波超声电机接触特性研究

电接触法是测试超声电机定转子接触状态的有效方法,但目前该方法主要用来研究电机堵转时的定转子接触状态,没有进行电机旋转时的接触状态的测试。针对该问题,对电接触法进行改进,使之可以测试电机旋转时的接触状态。基于改进后的电接触法分别对超声电机堵转和空载情况下定转子相对接触长度进行测试。结果表明,空载时定转子相对接触长度要小的多,与堵转时的最大差值约为36%。说明负载对超声电机接触状态有不可忽视的影响。最后,基于黏弹性接触模型对电机空载时定转子接触状态进行仿真计算,结果与实验值有很好的一致性,表明改进后的电接触法可有效的测试电机动态接触状态。     

基于电接触法的行波超声电机接触特性研究

电接触法是测试超声电机定转子接触状态的有效方法,但目前该方法主要用来研究电机堵转时的定转子接触状态,没有进行电机旋转时的接触状态的测试。针对该问题,对电接触法进行改进,使之可以测试电机旋转时的接触状态。基于改进后的电接触法分别对超声电机堵转和空载情况下定转子相对接触长度进行测试。结果表明,空载时定转子相对接触长度要小的多,与堵转时的最大差值约为36%。说明负载对超声电机接触状态有不可忽视的影响。最后,基于黏弹性接触模型对电机空载时定转子接触状态进行仿真计算,结果与实验值有很好的一致性,表明改进后的电接触法可有效的测试电机动态接触状态。     

A finite volume method and experimental study of a stator of a piezoelectric traveling wave rotary ultrasonic motor

Piezoelectric traveling wave rotary ultrasonic motors are motors that generate torque by using the friction force between a piezoelectric composite ring (or disk-shaped stator) and a metallic ring (or disk-shaped rotor) when a traveling wave is excited in the stator. The motor speed is proportional to the amplitude of the traveling wave and, in order to obtain large amplitudes, the stator is excited at frequencies close to its resonance frequency. This paper presents a non-empirical partial differential equations model for the stator, which is discretized using the finite volume method. The fundamental frequency of the discretized model is computed and compared to the experimentally-measured operating frequency of the stator of Shinsei USR60 piezoelectric motor.     

高分辨特性压电行波旋转马达研究

本文对一种压电行波型旋转超声马达进行了理论与实验研究。采用有限元方法对行波马达驱动定子的各阶振动模式、谐振频率进行了分析;研制的行波马达具有以下特点：低转速（0－50r.p.m）、较大力矩输出（0~1.9kgf.cm）、自锁功能、高的角分辨率和定位精度（±0.15°）。     

A traveling wave ultrasonic motor of high torque

A traveling wave ultrasonic motor of high torque with a new configuration is proposed in this paper. In the new design, a part of the motor serves as the stator. The rotor is the vibrator consisting of a toothed metal ring with piezoelectric ceramic bonded, which generates ultrasonic vibration. The rotor is in contact with the shell of motor and is driven by the friction between the rotor and the stator. This configuration not only removes the rotor in a conventional type of traveling wave ultrasonic motor but also changes the interaction between the rotor and the stator of the motor so that it improves the output performance of the motor. Although an electric brush is added to the ultrasonic motor, it is easy to be fabricated because of the low speed of motor. The finite element method was used to compute the vibration modes of an ultrasonic motor with a diameter of 100mm to optimize the design of the motor. A 9th mode was chosen as the operation mode with a resonance frequency about 25 kHz. According to the design, a prototype was fabricated. Its performance was measured. The rotation speed-torque curves for various frequencies were obtained. The result shows that its stall torque is greater than 4 Nm within a range of 400 Hz. This ultrasonic motor was used to drive the window glass of a mobile car and the result was satisfactory. In the further the research on the friction material between the stator and the rotor is under way to improve the efficiency of the ultrasonic motor.     

圆板型压电行波马达及振动解析

依据克希霍夫薄板四点假设建立求解圆板状行波马达定子特征频率参数及其主振型的线性方程组,采用Matlab5.2工程分析与数值计算软件,利用行列式搜索算法精确求解了定子复合板内、外径比分别为0.1、0.3、0.35、0.6,对应不同振动模式时的特征频率因子及其主振型,并进一步利用牛顿插值法详细解析了马达定子在各阶振动模式下横向幅值的分布以及板面能量的分布情况,为马达定子的优化设计提供了理论依据,并根据数值分析结果总结出超声马达振动模式的选用原则.     

板状行波马达简化电学模型的建立

提出一种利用具有等同振动特性的1/2波长马达定子来建立圆板型行波超声马达电学模型的方法,该方法结合马达定子复合板振动模式的特点,直接利用哈密顿原理对行波型马达定子的等效电路进行精确求解。模型反映了行波马达形成机理,同时计入了马达高阶非轴对称振动模式、齿的结构尺寸、压电陶瓷各向异性等要素。利用该方法可求解行波型马达在各阶常用振动模式下的静态电容、动态电容、动态电感、动态电阻、等效输入阻抗等电学参数,与实验测试达到了很好的一致性。     

Characteristics of ring type traveling wave ultrasonic motor in vacuum

The characteristics of ultrasonic motor strongly depend on the properties of stator/rotor contact interface which are affected by ambient environment. With the developed apparatus, load properties of two ring type traveling wave ultrasonic motors in atmosphere, low vacuum and high vacuum were studied, respectively. Wear of friction material, variations of vacuum degree and the temperature of motor during the experiment were also measured. The results show that load properties of motor A in vacuum were poorer than those in atmosphere, when load torque M_f was less than 0.55 N m. Compared to motor A, load properties of motor B were affected a little by environmental pressure. Wear of friction material in vacuum was more severe than wear in atmosphere. The temperature of motor in vacuum rose more quickly than it in atmosphere and had not reached equilibrium in 2 h experiment. However, the temperature of motor in atmosphere had reached equilibrium in about forth minutes. Furthermore, outgas was also observed during experiment under vacuum conditions.     

环形行波式超声马达解析模型的仿真与实验研究

在假定超声马达的定子为圆板,定子与转子的接触符合刚体与分布弹簧模型的条件下,通过理论分析,建立超声马达输出特性的解析模型,并完成其仿真和实验研究。仿真和实验结果基本吻合,证明了该模型的有效性。     

Characteristic model of travelling wave ultrasonic motor

In general, the design and analysis of ultrasonic motor and motor’s control strategy are based on mathematical model. The academic model is widely used in the analysis of traveling wave ultrasonic motor (TWUSM). But the dispersive characteristic of piezoelectric ceramics and other complicated process, such as the friction, make the model’s precision not so accurate. On the other hand, identification modeling method, which is built based on the tested data, has obtained increasing application in the study of ultrasonic motor’s control technology. Based on the identification model, many control strategies can be designed easily. But the identification model is an approximate model, so if a more accurate model of ultrasonic motor can be obtained, the analysis and design of motor control system will be more effective. Characteristic model is a kind of identification model which can accurately describe the characteristics of TWUSM. Based on the tested data, this paper proposes the modeling method of ultrasonic motor’s characteristic model. The paper also makes a comparison of the effectiveness of different identification algorithms. Aiming at the speed control of ultrasonic motor, the influence of the parameter’s initial values on the precision of model is discussed. The calculating results indicate the availability of this characteristic model.     

声表面波驱动的转动马达研究

在128°旋转Y切割x方向传播的LiNbO₃基片表面平行地光刻两对工作频率为30MHz的叉指换能器(IDT)作为定子,当高频电压加在IDT1和IDT3(或IDT2和IDT4)时,基片上将产生两列平行但方向相反的瑞利波束,从而使得基片与其上部的转子间存在局部地相对运动,在滑动摩擦力偶的作用下转子经过加速后运动趋于稳定。本文给出了工作频率为30MHz的声表面波转动马达的一些实验测量结果:在120V_p-p的电压驱动下,马达经过400ms的加速后,转动速度达到稳定,约为270rpm,并对其工作机理进行了理论分析及计算。     

An electric contact method to measure contact state between stator and rotor in a traveling wave ultrasonic motor

Performances of ultrasonic motor (USM) depend considerably on contact state between stator and rotor. To measure the contact state in a traveling wave ultrasonic motor (TWUSM), a special test method is necessary. This paper develops a new method named electric contact method to measure contact state of stator and rotor in traveling wave type USM. The effects of pre-load and exciting voltage (amplitude) of stator on contact state between stator and rotor are studied with this method. By a simulating tester of friction properties of TWUSM, the variations of stalling torque and no-load speed against the pre-load and the exciting voltage have been measured. The relative contact length that describes the contact characteristic of stator and rotor is proposed. The relation between the properties of TWUSM and the contact state of stator and rotor are presented. Additionally, according to a theoretical contact model of stator and rotor in TWUSM, the contact lengths at given conditions are calculated and compared with the experimental results.     

超声马达定子齿运动模型的建立

超声波马达作为一种新型的小马力电机已引起科研人员的极大关注.本文中,作者利用解析法建立了行波型超声波马达定于齿的运动学模型,这对进一步研究转子与定子间的接触模型是至关重要的.同时,我们采用有限元法研究了马达在各阶振动模式下接触点位移、马达共振频率与齿高的变化规律,发现齿高在从3mm到9mm的区间变化时,对接触点圆周方向的位移影响较大,特别是在高阶(9,0)振动模式下,而径向位移在齿高6mm左右时基本趋于饱和。我们依据齿的运动数学模型研制出一种新型的三维接触式超声波马达.     

Motion modeling for teeth of traveling wave ultrasonic motors

1IntroductionAtravelingwavultrasonicmotor,asafractionalhorsepowermotor,isdtherentfromconventionalelectromagneticmotor.Itcombinesfeaturessuchaslight-weightpackage,highdrivingtorqueatlowspeed,qulckresponse,lowconsume,zerobaCklash,seifbrakingatzeropower,noelectromagneticdisturbanceandnoise,andhighheat-stabilltyinwickedenvironmellt,etc.Hence,ultrasonicmotorsmaybeusedinareas:camraautofocuslenses,medicalaPParatus,ndcrrvrobots,ndcrcasatellites,micro-pumpsforinjection,etc.l1-4]Inordertounderstandthe…     

压电管式弯曲旋转超声电机激励模式研究

为了提高压电管式弯曲旋转超声电机输出特性,推导出定子一、二阶弯曲振动下力系数的计算公式。结果表明,利用定子二阶弯曲振动可获得更大的定子端面输出力。提出了一种将定子分为8个激振区的交叉组合激励模式,可实现定子的二阶弯曲振动激励。基于这种新的激励模式,研制了一台压电管式弯曲旋转超声电机的样机,该样机的定子外径10 mm、内径8 mm、长35 mm。在预压力1.0 N,激励电压峰峰值210 V,工作频率41.3 kHz时,实现了定子的二阶弯曲振动,样机的堵转转矩达到2.45 N·mm,空载转速为206 r/min。与将定子分为4个激振区的同尺寸的超声电机相比,堵转转矩和空载转速分别提高了17%和23%。     

响应面法的杆式超声电机有限元模型修正

现有杆式超声电机的有限元模型大都采用连续复合材料的简化结构形式,忽略了实际超声电机各部件间的接触特性,导致计算结果与实验结果具有较大偏差。针对该问题,提出了一种采用响应面法的杆式超声电机有限元模型修正方法,来获得高精度的有限元模型。该方法考虑了超声电机螺栓预紧力及各部件接触界面的法向接触刚度和摩擦系数,筛选出显著影响电机工作模态的参数,建立响应面模型替代超声电机的有限元模型实现快速计算结构响应的目的,并以实验模态分析结果为目标对模型进行修正。修正结果表明,修正后的模型模态频率的平均误差由修正前的1.20%降到0.21%,模型精度得到明显改善,表明以响应面的有限元模型修正方法对杆式超声电机以及类似夹心式压电振子的设计具有应用价值。     

Mode-splitting and quasi-degeneracies in circular plate vibration problems: The example of free vibrations of the stator of a traveling wave ultrasonic motor

In systems with rotational symmetry, bending modes occur in doubly-degenerate pairs with two independent vibration modes for each repeated natural frequency. In circular plates, the standing waves of two such degenerate bending modes can be superposed with a 1/4 period separation in time to yield a traveling wave response. This is the principle of a traveling wave ultrasonic motor (TWUM), in which a traveling bending wave in a stator drives the rotor through a friction contact. The stator contains teeth to increase the speed at the contact region, and these affect the rotational symmetry of the plate. When systems with rotational symmetry are modified either in their geometry, or by spatially varying their properties or boundary conditions, some mode-pairs split into singlet modes having distinct frequencies. In addition, coupling between some pairs of distinct unperturbed modes also causes quasi-degeneracies in the perturbed modes, which leads their frequency curves to approach and veer away in some regions of the parameter space. This paper discusses the effects of tooth geometry on the behavior of plate modes under free vibration. It investigates mode splitting and quasi-degeneracies and derives analytic expressions to predict these phenomena, using variational methods and a degenerate perturbation scheme for the solution to the plate’s discrete eigenvalue problem; these expressions are confirmed by solving the discrete eigenvalue problem of the plate with teeth.     

行波型超声电机定子的共振与反共振特性的研究

针对行波型超声电机定子在共振和反共振点附近表现的不同特性,以压电陶瓷材料大功率驱动下的理论分析和电学分析为基础,通过对实验现象的描述和分析,确立了以频率、机械谐振品质因数、机电耦合系数和相对振动效果等参数作为定量和定性分析定子共振和反共振的性能指标。在实验研究中,以激光测振为直接实验手段,设计了相关实施方案,对行波型超声电机定子在不同驱动方式下表现出的共振和反共振特性进行了分析和对比研究。研究结果表明,行波型超声电机定子在反共振点附近的综合性能要优于共振点附近的性能,实验结果可为行波型超声电机工作状态以及驱动方式的选择提供依据和指导。