Wear and dynamic properties of piezoelectric ultrasonic motor with frictional materials coated stator

Piezoelectric ultrasonic motors have been studied, developed and utilized by researchers and companies all over the world. Ultrasonic motors (USM) produce rotational motion based on traveling waves made by the resonant vibrations of piezoceramic. These motors have been recently developed and utilized in practical applications. The dynamic properties and life of piezoelectric ultrasonic motors are strongly related to the frictional material Fused on the sliding surface. In this study, effects of frictional material properties on the performances of piezoelectric ultrasonic motors are investigated. It was possible to improve the torque of a traveling wave type ultrasonic motor by stator's coating.     

New type of linear ultrasonic actuator based on a plate-shaped vibrator with triangular grooves

This paper presents a new type of linear ultrasonic actuator that can drive a slide by ultrasound. The ultrasonic actuator consists of a metal plate with uniform triangular grooves, multilayer piezoelectric vibrator, and supporting structure. The multilayer piezoelectric vibrator is used to excite a flexural vibration in the metal plate that is adjusted to lie horizontally. When the metal plate vibrates, a glass slide on it is levitated in the vertical direction and linearly driven along the length direction. Experimental characteristics of the prototype are presented here. This is the first report case of using the sound field that is generated by a grooved metal plate, to drive a slide levitated by acoustic radiation force.     

A flexible piezoelectric transducer design for efficient generation and reception of ultrasonic Lamb waves

This paper describes the development of a flexible piezoelectric transducer for the generation and detection of ultrasonic symmetrical Lamb waves in plate-like structures. This piezoplatelet transducer structure comprises an array of miniature piezoceramic plates embedded within a soft setting polymer filler material, combining the efficiency of the active piezoceramic phase with a degree of flexibility, which is a function of the platelet/polymer dimensions. For many condition-monitoring applications, the generation of ultrasonic Lamb waves is often appropriate, and this was achieved by incorporating interdigital design techniques via the transducer electrode pattern. The performance of the piezoplatelet transducer structure was evaluated using a combination of linear systems and finite-element modeling, substantiated by experimental results. Importantly, the transducer is shown to operate as an ensemble of platelets, each operating in the thickness mode and well decoupled from neighboring piezoelectric elements. Using this transducer configuration, an unimodal s1 Lamb wave, at 1.45 MHz, has been generated and detected in a 3-mm thick steel plate. Furthermore, a propagation distance of almost 1 m was recorded for s0 Lamb wave generation/detection in a fiber-reinforced composite plate.     

Fabrication and experimental characterization of d31 telescopic piezoelectric actuators

A popular and useful piezoelectric actuator is the stack. Unfortunately with this type of actuation architecture the long lengths normally required to obtain necessary displacements can pose packaging and buckling problems. To overcome these limitations, a new architecture for piezoelectric actuators has been developed called telescopic. The basic design consists of concentric shells interconnected by end-caps which alternate in placement between the two axial ends of the shells. This leads to a linear displacement amplification at the cost of force; yet the force remains at the same magnitude as a stack and significantly higher than bender type architectures. This paper describes the fabrication and experimental characterization of three different telescopic prototypes. The actuator prototypes discussed in this paper mark a definitive step forward in fabrication techniques for complex piezoceramic structures. Materials Systems, Inc. has adapted injection molding for the fabrication of net shape piezoceramic actuators. Injection molding provides several advantages over conventional fabrication techniques, including: high production rate, uniform part dimensions, uniform piezoelectric properties, and reduced fabrication and assembly costs. Acrylate polymerization, developed at the University of Michigan, is similar to gelcasting, but uses a nonaqueous slurry which facilitates the production of large, tall, complex components such as the telescopic actuator, and is ideal for the rapid manufacture of unique or small batch structures. To demonstrate these fabrication processes a five tube telescopic actuator was injection molded along with a very tall three tube actuator that was cast using the acrylate polymerization method. As a benchmark, a third actuator was built from off-the-shelf tubes that were joined with aluminum end-caps. Each prototype's free deflection behavior was experimentally characterized and the results of the testing are presented within this paper.     

Coupled tangential-axial resonant modes of piezoelectric hollow cylinders and their application in ultrasonic motors

This paper describes a tangential-axial eigen-mode of a piezoelectric hollow cylinder. A new type of piezoelectric ultrasonic motor using this oscillation mode has been developed. The motor is a traveling-wave-type motor. The stator of such a motor consists of a solid piezoelectric hollow cylinder, which, excited in the tangential-axial resonant mode by a three-phase electrical signal, will exhibit elliptical displacement and transfer rotation to the rotor. The behavior of the stator has been simulated with finite element method (FEM) software. The simulation results have been checked with single-point contact measurements on the surface of the ultrasonic motors. The paper closes with the introduction of new ultrasonic motors based on this oscillation mode.     

Pointwise fiber Bragg grating displacement sensor system for dynamic measurements

A method for setting up a fiber Bragg grating (FBG) sensor which can measure the pointwise, out-of-plane or in-plane dynamic displacement is proposed. The proposed FBG sensor is reusable. A multiplexing demodulation system based on a single long-period fiber grating is used in this study. The experimental results of the steady-state motion for a multilayer piezoelectric actuator and the dynamic response of a cantilever beam subjected to impact loadings are presented. These results indicate that the proposed displacement sensor has the ability to measure the out-of-plane dynamic displacement with high sensitivity. Measurements for a piezoceramic plate excited by high frequency show that the proposed displacement sensor also has the ability to provide the in-plane dynamic displacement up to 20 kHz.     

Ultrasonic piezoceramic transducers with a magnetoacoustic layer

We describe the design and present the results of calculations of the properties of an ultrasonic transducer based on a piezoceramic plate in mechanical contact with a layer of a magnetoacoustic material. The transducer is characterized by strong dependence of the velocities of both transverse and longitudinal waves on the magnetic field. This allows the resonance frequency and the bandwidth to be effectively controlled even in the case of low-Q piezoelectric ceramics and makes it possible to create a tunable frequency standard based on a high-Q piezoelectric material.     

Active vibration control of composite plate with optimal placement of piezoelectric patches

The active vibration control of a composite plate using discrete piezoelectric patches has been investigated. Based on first order shear deformation theory, a finite element model with the contributions of piezoelectric sensor and actuator patches to the mass and stiffness of the plate was used to derive the state space equation. A global optimization based on LQR performance is developed to find the optimal location of the piezoelectric patches. Genetic algorithm is adopted and implemented to evaluate the optimal configuration. The piezoelectric actuator provides a damping effect on the composite plate by means of LQR control algorithm. A correlation between the patches number and the closed loop damping coefficient is established.     

Finite element simulation for a new disc-type ultrasonic stator

This paper is concerned with the development of a new disc-type piezoelectric ultrasonic stator. Linear piezoelectric, mechanical, and piezoelectro-mechanic behaviors of a metal disc structure embedded with piezoelectric actuator are considered. Using a finite element method, a dynamic formulary is modeled for the new disc-type piezoelectric ultrasonic stator. In this model, a 3-dimensional (D) mechanical element with an extra electrical degree of freedom is used to simulate dynamic vibration modes and analyze characteristic responses such as electrical impedance response, phase response, and mechanical frequency response for a new disc-type piezoelectric ultrasonic stator. An adaptive boundary condition, simple support condition with three nonequal-triangular fixed points near the edge for the mechanism design of a new disc-type piezoelectric ultrasonic stator is defined so that a lateral elliptical motion of the contact point between stator and rotor can be realized for driving the rotor. The finite element results have been compared with the experimental measurements. As a result, the analysis model seems to be similar to the real condition.     

A coupled-mode theory for periodic piezoelectric composites

A coupled oscillator model to calculate the resonance spectrum of a one-dimensional piezoelectric composite plate, used in ultrasonic transducers, is proposed. Two resonant modes, one produced by the elastic wave reflection on the plate boundaries (thickness resonance) and the other by the reflection on the periodic discontinuities (lateral resonance) are considered. A Kronig-Penney model is used to calculate the lateral resonances. The thickness resonance is obtained with an effective medium model. The coupling of these two modes is described by a biquadratic equation whose solutions are the resonant frequencies of the piezoelectric composite plate. A criterion for a distribution of phases to keep the spurious lateral resonances away from the thickness resonance vicinity is obtained.     

Finite element analysis for geometrically nonlinear deformations of smart functionally graded plates using vertically reinforced 1-3 piezoelectric composite

In this paper, a finite element model has been developed for the geometrically nonlinear static analysis of simply supported functionally graded (FG) plates integrated with a patch of vertically reinforced 1-3 piezoelectric composite material acting as a distributed actuator. The material properties of the functionally graded substrate plate are assumed to be graded only in the thickness direction according to the power-law distribution in terms of the volume fractions of the constituents. The analysis of the electro-elastic coupled problem includes the transverse deformations of the overall plate to utilize the transverse normal actuation by the distributed actuator for counteracting the nonlinear deformations of smart functionally graded plates. The nonlinear governing equations of equilibrium are solved by using direct iteration method with under-relaxation. The numerical illustrations suggest the potential use of the distributed actuator made of vertically reinforced 1-3 piezoelectric composite material for active control of nonlinear deformations of smart functionally graded plates. The effect of variation of piezoelectric fiber orientation in the distributed actuator on its control authority for counteracting the nonlinear deformations of smart functionally graded plates has also been investigated.     

Active damping of piezo-composite beams

The aim of the present study is to investigate the effects of piezoceramic materials on the active damping of vibrating piezo-composite beams. The active damping is obtained by using an actuator and a sensor piezoceramic layer acting in ‘closed-loop’. By transferring the accumulated voltage on the sensor layer to the piezoelectric actuator layer, the beam can actively damp-out its vibrations. An exact mathematical model, based on a first order shear deformation theory (FSDT) is developed and described. This model allows the investigation of piezo-composite beams with two actuation/sensing type mechanisms, extension and shear. The present study is confined to symmetric lay-up beams using continuous piezoelectric layers. Using the present model, both natural and damped vibrations are calculated. The effects of the feedback gain, G, and the beam length on the damped vibrations are investigated and presented.     

A New Discrete-Layer Finite Element for Electromechanically Coupled Analyses of Piezoelectric Adaptive Composite Structures

A new discrete layer finite element (DLFE) is presented for electro-mechanically coupled analyses of moderately thick piezoelectric adaptive composite plates. The retained kinematics is based on layer-wise first-order shear deformation theory, and considers the plies top and bottom surfaces in-plane displacements and the plate transverse deflection as mechanical unknowns. The former are assumed in-plane Lagrange linear, while the latter is assumed in-plane full (Lagrange) quadratic; this results in a nine nodes quadrangular (Q9) DLFE. The latter is validated in free-vibrations, first numerically against ANSYS three-dimensional piezoelectric finite elements for a cantilever moderately thick aluminum plate with two co-localized piezoceramic patches, and then experimentally against a free quasi-isotropic transverse composite thin plate with four piezoceramic patches. The obtained short-circuit and open-circuit (OC) frequencies were satisfactory for both benchmarks, while the post-treated modal effective electromechanical coupling coefficients agreed well with ANSYS results (first benchmark) but only fairly with the experimental ones (second benchmark). Once validated, the Q9-DLFE was used to assess numerically the equipotential (EP) physical condition influence on the OC sensed electric potential; for this purpose, the above first benchmark, but with the top piezoceramic patch only, was finally analyzed. It was found that the EP condition homogenizes and lowers the sensed potential on the OC electrode.     

层合板中压电作动器最优厚度和嵌入位置研究

研究了压电结构中压电片厚度和嵌入深度的优化问题。首先给出了压电层合板的高阶耦合分析模型;然后以不受约束的含压电铺层复合材料板为代表,在压电层厚度方向施加电场时板自由变形,假设板任意微元横截面上内力为零,以其弯(扭)曲曲率最大为优化目标,建立了求解压电片最优厚度和嵌入深度问题的约束优化模型。最后分别以各向同性板中嵌入各项同性压电片和复合材料板中嵌入各向异性压电片为例进行了分析,绘出了目标函数的三维曲面图及等高线图,结果表明压电片的作动效能与其厚度和嵌入位置密切相关,而最优厚度和嵌入位置是由压电片和基体的材料特性决定的。     

基于模态应变能分布的压电致动器/传感器位置优化遗传算法

本文由线弹性压电结构有限元动力方程,推导了压电智能结构的振动控制方程。建立了准确模拟层合压电结构动力行为的有限元模型。基于主结构模态应变能分布提出了一种新的优化目标函数,将压电致动器/传感器位置编号作为优化变量,建立了离散变量表示的智能结构优化问题,并通过二进制编码的遗传算法（GA）求解了该最优问题。以四边固支复合层合压电智能板为数值算例,采用比例反馈控制, 研究了最优位置配置致动器/传感器智能结构目标模态的控制效果。数值结果表明基于模态应变能分布的遗传算法所得优化解具有较好的振动控制效果。     

Performance improvement of rectangular-plate linear ultrasonic motors using dual-frequency drive

To improve the performances of a rectangular-plate linear ultrasonic motor for specific applications, a dual-frequency drive has been proposed and investigated. Through careful design of the rectangular piezoelectric ceramic plate, its first longitudinal resonant frequency coincides with its second lateral bending resonant frequency and is one-third of its higher lateral bending resonant frequency. When a square-wave voltage is used to drive the motor, its first longitudinal and second bending and the higher bending vibration modes are excited. Experimental results show that the maximum thrust force and maximum velocity of the motor are over 170% of those obtained from the single-frequency sine-wave drive when the voltage performance of the motor becomes saturated.     

基于性能可调阶梯型变幅杆的超声波振子调谐研究

为减小超声波振子外接负载时其谐振频率漂移的幅度,使用机电等效电路法和COMSOL Multiphysics 5.3有限元仿真软件设计制造了一种基于性能可调阶梯型变幅杆的超声波振子。对该超声波振子的谐振频率进行有限元仿真和现场测试。以超声清洗机为例,搭建与其原理相似的试验装置,以不同液面高度的水作为变幅杆的外接负载,探究在不同外接负载情况下,调节连接在变幅杆处压电晶堆的调谐电感对解决超声波振子谐振频率漂移问题的有效性。试验结果表明：随着水杯中液面高度的增加,超声波振子的谐振频率整体呈上升趋势;通过在变幅杆的压电晶堆处外接调谐电感,超声波振子的谐振频率会得到一定的补偿,可重新回归到原始设定的谐振频率值附近。研究表明在使用超声波振子进行超声辅助加工时,该超声波振子对减小外接负载引起的谐振频率漂移幅度具有一定作用。研究结果可为超声波振子的调谐提供新思路和新方法。     

Improved Sensitivity in the Impedance Method of Determining the Resonant Frequency of a Piezoelectric Detector

Connecting a piezoceramic capacitor into an arm of a capacitance bridge allows one to use an impedance method to determine the resonant frequency of a low-sensitivity piezoelectric sensor.     

国外压电陶瓷声马达的发展近况

压电陶瓷声马达是一种利用压电陶瓷基片基片或薄膜,电致伸缩材料等功能部件实现驱动的新型驱动器,它不同于传统的电磁马达和静电马达,国外已经在精密仪器,航天航空,自动控制,办公自动化,微型机械系统,微装配,精密定位等领域得到了实际应用,总结了国际上压电陶瓷声马达的最新研究内容及成果,并提出了进一步开发研究的几点建议,这对我国压电声马达的研究以及相应产品的开发将起到积极的促进使用。     

The influence of electrode designs on the resonant vibrations for square piezoceramic plates

In this paper, the resonant vibrations of square piezoceramic plates with four different electrode designs are investigated. Two experimental techniques, the amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and the impedance analysis, are used to access the influence of the electrode arrangement on the resonant characteristics of square piezoceramic plates. Both the out-of-plane and in-plane resonant frequencies and full-field mode shapes of piezoceramic plates with various electrode designs are obtained from the AF-ESPI method. The impedance analyzer is used to measure the resonant and antiresonant frequencies of piezoceramic plates. The dynamic electromechanical coupling coefficient (EMCC), which relates to the ability of conversion between mechanical and electrical energy, is determined from the measured values of resonant and antiresonant frequencies. Experimental results of the resonant vibration characteristics of the square piezoceramic plates are verified by numerical computations based on the finite-element method. Excellent agreement between the experimental and numerical results is found in resonant frequencies and corresponding mode shapes. It is found that the electrode design has important influence on the resonant characteristics of piezoceramic plates. The effect of different designs of electrode is more significant in the in-plane modes than that in the out-of-plane modes.