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。     

Design of a hybrid transducer type ultrasonic motor

The authors present a design method for a hybrid transducer-type ultrasonic motor (HTUSM) for practical use. They introduce a simple equivalent circuit that expresses the unique operation mechanism of the hybrid transducer-type motor. A numerical simulation based on the model enables them to predict the motor characteristics such as the maximum torque and the no-load revolution speed. In addition, for the purpose of efficient design and physical interpretation of the phenomena, they discuss analytically the maximum torque of a special case and develop two design charts for the prediction of the no-load speed of the motor.     

纵弯复合多自由度球形超声电机的研究

摘 要：目前国内外对多自由度超声电机的研究和应用尚属探索阶段,出现了多种结构的多自由度超声电机。本文提出了一种新型单振子纵弯夹心换能器式超声电机结构,由单一驱动足产生多自由度振动轨迹,驱动球形转子作多自由度运动;对十字交叉换能器做了模态分析,对纵振和弯振做了模态简并;建立了驱动足的运动轨迹方程,并仿真分析了典型驱动方式下驱动足的振动轨迹;试验测试了样机转子绕X、Y、Z轴转动的速度与电压之间的关系和转矩与速度之间的关系,计算了相应情况下电机的最大效率;电机旋转方向与分析结果一致。
     

Improvement of the longitudinal vibration system for the hybrid transducer ultrasonic motor

This paper presents a symmetric hybrid transducer ultrasonic motor designed to produce large longitudinal vibration stress in the rotor/stator contact interface for high-torque operation. The nodal plane of the longitudinal vibration mode was adjusted to match the rotor/stator contact interface, and the piezoelectric ceramic disks for the longitudinal vibration were installed at the nodal plane of the longitudinal vibration mode for effective excitation. An experimental motor, 20 mm in diameter, using the first torsional vibration mode and the second longitudinal vibration mode was manufactured. A maximum torque of 0.8 N.m was achieved in the prototype, an improvement over previous versions.     

Characteristics of a hybrid transducer-type ultrasonic motor

The hybrid transducer-type ultrasonic motor previously proposed by the authors (1989, 1991) uses two ultrasonic transducers to control the Lissajous figure at the contact surface of the stator. This motor is stable, even at low speed, and realizes a large output with a high efficiency due to the high controllability of the Lissajous figure. The experimental investigation of the characteristics of this hybrid transducer-type ultrasonic motor is presented. In addition, the maximum torque is roughly estimated by means of a simple model. The dependence of the diameter of the motor (transducer) on the maximum torque is discussed and demonstrated experimentally.     

An ultrasonic motor using bending vibrations of a short cylinder

An ultrasonic motor using bending vibrations of a short cylinder with free-free ends is proposed, and its performance and efficiency are discussed. The motor is small in size and realizes a high mechanical output of more than 1 W. The general principle of the motor, which uses traveling waves, is as follows. When a traveling wave propagates along an elastic object, particles at the surface move elliptically. A movable object (a slider or a rotor) pressed to the elastic object may be caused to move due to the frictional forces between it and the surface. A motor based on this principal has been constructed and studied. The vibration mode used is found to have an undesirable radial component, which restricts the efficiency of the motor to about 10% at best. A large amount of the energy supplied is lost by the slippage owing to the existence of the undesirable component. It is concluded that to derive larger output power, the frictional material needs to be carefully chosen.     

Design of a traveling wave type ultrasonic motor

The purpose of the present paper is to establish a method of design for a traveling wave type ultrasonic motor. This method is based on two models for the ultrasonic motor. A two-dimensional elastic contact model is used for estimating the friction drive between the rotor and vibrator of the motor. Moreover, an electrical equivalent circuit is used to estimate the interaction between the electrical and mechanical parts of the vibrator. The proposed method is applied to the design of a prototype motor. To determine applicability of the method, the load characteristics of the prototype motor are measured. The measured characteristics agree with the required ones which are specified in advance. As a result, the validity of the proposed method is experimentally confirmed     

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.     

Optimization of a new type of ultrasonic linear motor

This paper presents the design, the properties, and the optimization study of a new type of ultrasonic linear motor. Numerical modeling has been carried out and simulations with software have been realized. To avoid performing a large number of simulations, sensitivity analysis has been carried out, in particular using design of experiments. The Doehlert method has been chosen in our study. The results found show that this preoptimization stage allows one to improve the deformation amplitude and to reduce the input parameter variation ranges. Finite element (FE) optimization is then carried out, and results show that the motion amplitudes can be increased compared to the initial design of the motor. Some experiments on prototypes show that the travel range of the motor has been increased while decreasing the applied voltage by a factor of 2.     

New type of piezoelectric ultrasonic motor

The authors describe a newly developed motor concept which allows a bidirectional piezoelectric ultrasonic motor to be operated with only a single voltage feed and thus only one power amplifier. The motor concept is based on the superposition of a longitudinal and a flexural oscillation of a rod-shaped resonator. In a way analogous to the generation of a Lissajous figure, this superposition produces a rotary movement of the resonator end by means of which a rotor is directly driven. By selecting the relative phase of the electrical stimulations of both modes, the speed can be continuously varied in both directions. The motor can be driven in both right and left directions with speeds of 0 to 300 r/min, and a freewheeling state can be set up by means of a suitable phase between the oscillation modes. In the off state, the motor blocks the motion.     

Characteristics estimation of a traveling wave type ultrasonic motor

A method for calculating the load characteristics of a traveling-wave-type ultrasonic motor (TWUM) is proposed. A systematic method using an equivalent circuit is suggested for estimating the performance of the motor, including its electrical and the mechanical parts. In the proposed method, a governing equation for the motor is derived to describe the relation between the applied voltage at an electrical terminal, vibration velocities, and the external forces at mechanical terminals of a vibrator. A method for estimating the forces between the rotor and the vibrator of the motor is presented and used to calculate the load characteristics. The numerically calculated load characteristics are shown to agree well with the measured ones, confirming the validity of the method.     

A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet

A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet was proposed in this paper. The proposed motor contains a horizontal transducer and two vertical transducers. The horizontal transducer includes two exponential shape horns located at the leading ends, and each vertical transducer contains one exponential shape horn. The horns of the horizontal transducer and the vertical transducer intersect at the tip ends where the driving feet are located. Longitudinal vibrations are superimposed in the motor and generate elliptical motions at the driving feet. The two vibration modes of the motor are discussed, and the motion trajectories of driving feet are deduced. By adjusting the structural parameters, the resonance frequencies of two vibration modes were degenerated. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 854 mm/s and maximum thrust force of 40 N at a voltage of 200 V(rms).     

复合型超声马达纵-扭振动固有频率简并研究

纵、扭振动固有频率简并是提高纵-扭复合型超声马达输出力矩的关键问题。然而同一弹性体内的纵振固有频率远高于扭振固有频率．目前对两种振动固有频率的简并缺乏深入的理论研究。纵一扭复合型超声马达振动分析模型都基于一维理论。在此提出了一种纵、扭振动固有频率简并的新方法。通过将纵一扭复合型超声马达设计成双定子对称结构．在定子上附加一个调整环改变定子的力学边界条件。实现纵、扭振动同频共振。应用Hamilton原理建立了考虑泊松效应的定子纵、扭振动理论模型，分析了定子的纵振与扭振第一阶固有频率随调整环质量和位置的变化规律，通过优化马达的几何结构参数获得了纵振与扭振的同频谐振点。     

Development of a novel ultrasonic motor resonator using topology optimization

The use of topology optimization in the design of a novel stator for an ultrasonic motor (USM) is investigated. The design challenge is to produce a stator, with two resonant modes whose frequencies are in a ratio of 1:2. When driven together, these modes result in a contact point trajectory in a figure of eight shape. As a result, only one electronic amplifier is required to drive the proposed device. In contrast traditional travelling wave USM, with elliptical contact point trajectories, require two modes with equal resonant frequencies to be driven 90° out of phase, and therefore require two amplifiers, one for each mode. To achieve a suitable stator design, a slightly unconventional topology optimization problem formulation is proposed, in which the objective function is to minimize the amount of material with intermediate density, while satisfying a constraint related to the frequency ratio of selected resonant modes. The planar design produced using the optimization procedure was refined using a detailed three dimensional finite element analysis. A prototype of the proposed stator design was manufactured and experimentally characterized. Scanning laser vibrometry measurements from two positions were used to measure the figure of-eight motion. Finally, the stator was fitted with a preloaded slider to form a simple linear motor demonstrator which was characterized experimentally. The prototype motor produced a slider speed of 14 mm/s reversibly and a maximum force of 50 mN.     

Developments of piezoelectric ultrasonic actuators operating under bending hybrid vibration modes

The exciting methods for the sandwich type piezoelectric ultrasonic actuators used bending hybrid modes are investigated. Five exciting methods are discussed and compared in detail, in which the polarizations and the partitions of the ceramic rings are different. Harmonic analyses are developed to obtain the effects of the exciting methods on the electromechanical coupling factors and the vibration amplitudes. At last, five prototypes are manufactured to verify their differences. Both the simulation and experiment results prove that the exciting method using ceramic rings with four separated partitions achieves great improvements on the efficiency, velocity and force, synchronously.     

行波型杆式超声电机定子的参数化有限元法优化设计

摘要：利用参数化有限元优化方法,对行波型杆式超声电机定子进行优化设计。首先,在确定电机定子初始结构的基础上,建立其参数化有限元模型。其次,对定子有限元模型进行模态分析,求解工作模态频率对各结构参数的灵敏度,选取灵敏度高的结构参数为设计变量,并以反映电机输出性能的重要参数作为目标函数。同时,设计了定子结构的优化方案,采用了零阶优化方法,对其结构进行优化设计。最后,根据优化结果,制作了定子样机。试验表明：定子工作模态和端面质点的振幅都满足了预期的设计要求,试验结果与优化设计结果相符。研究表明,利用该优化设计方法能有效地缩短超声电机设计周期。     

Flexural vibration of a pyrocomposite hollow cylinder

Flexural vibration of an infinite pyrocomposite circular hollow cylinder composed of an inner and outer pyroelectric layer of class 6 bonded together by a linear elastic material with voids (LEMV) is studied. The exact frequency equation is obtained for traction-free surfaces with continuity conditions at the interfaces. Numerical results in the form of data and dispersion curves for the first and second modes of the flexural vibration of the cylinder ceramic-1/Adhesive/ceramic-2 by taking the adherents as BaTio₃ and the adhesive as an existing carbon fibre-reinforced polymer (CFRP) or as a hypothetical LEMV layer with and without voids are compared with that of a single-layered pyroelectric hollow cylinder. The damping is analyzed through the imaginary parts of the complex frequencies.     

新型超声波电机的研制及对比实验研究

从不同的振动模态出发,分别设计制作行波型旋转超声波电机和多振动片式驻波型超声波电机的样机,并分别对样机的性能进行测试,分析了不同类型电机的谐振频率、输入电压和预压力对其性能的影响．对这两种电机的效率、转矩进行了比较,得出了它们的优缺点。     

Force transfer model and characteristics of hybrid transducer type ultrasonic motors

The characteristics of longitudinal-torsional hybrid transducer-type ultrasonic motors (HTUSM) are low speed and high torque. The discontinuous-surface-contact mode between the stator and the rotor is different from the many-point-contact mode of traveling wave motors, which is also an essential cause for high torque. Therefore, it is important to analyze its force transfer model between the rotor and the stator. In this paper, issues of using the method of equivalent circuit model are addressed. The relationships between the contact angle, preload, and physical parameters of frictional materials are given, according to the impulse conservation law axially. The equations describing output torque, amplitudes of longitudinal and torsional vibration, and parameters of the rotor are derived according to the principle that the work done by the load is equal to that by the driving force in one vibrating cycle. All factors that influence the mechanical characteristics are analyzed, and accuracy and suitability of the force transfer model are verified by comparison with the prototype motor. The formula for transfer efficiency on the stator/rotor interface is given, and the low-efficiency of this type motor is explained. The wide-working frequency range property of this type motor is shown with experimental results. Based on this study, the parameters of the rotor and preload are determined. The maximum torque of the prototype motor is up to 13.2 nm, and no-load speed of this type of motor is 12.5 rpm.