Hybrid transducer type ultrasonic motor

A type of ultrasonic motor whose stator is composed of a torsional vibrator and multilayered piezoelectric actuators is proposed and has been fabricated for trial. The stator is operated at the resonance frequency of the torsional vibration. The vibrator generates the mechanical output force and the actuators control the frictional force. The construction provides for arbitrary Lissajous's figures at the contacting surface and contributes to large mechanical output power with high efficiency and bidirectional motion. It also gives greater freedom of design. The prototype motor produced a maximum torque of 7 kg-cm and a maximum efficiency of 33%     

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.     

Longitudinal-bending mode micromotor using multilayer piezoelectric actuator

Longitudinal-bending mode ultrasonic motors with a diameter of 3 mm were fabricated using stacked multilayer piezoelectric actuators, which were self-developed from hard lead zirconate titanate (PZT) ceramic. A bending vibration was converted from a longitudinal vibration with a longitudinal-bending coupler. The motors could be bidirectionally operated by changing driving frequency. Their starting and braking torque were analyzed based on the transient velocity response. With a load of moment of inertia 2.5 x 10(-7) kgm2, the motor showed a maximum starting torque of 127.5 microNm. The braking torque proved to be a constant independent on the motor's driving conditions and was roughly equivalent to the maximum starting torque achievable with our micromotors.     

Design and fabrication of a high performance multilayer piezoelectric actuator with bending deformation

A new bending mode multimorph actuator was designed and fabricated successfully by a multiple screen printing process. Unlike the conventional bimorph actuator in which the bend occurs in the thickness direction, the bend in the multimorph actuator occurs in the widthwise direction because of synchronistical deformation of each single monolithic layer in the multilayer structure. The theoretical analysis and experimental measurements were conducted to study the performance of this type of actuator, and a comparison was made with the conventional bimorph actuator. Larger displacement, higher resonance frequency, and much larger blocking force could be achieved with the multimorph actuator than with a bimorph actuator of similar dimensions. The multimorph actuator presented in this paper provides a valuable alternative for actuator applications beyond those available with the popular bimorph and longitudinal multilayer actuators.     

Design and fabrication of multilayer actuator using floating electrode

PZT (lead zirconate titanate) multilayer actuators were of interest due to their small volume, fast response, low power consumption and low driving voltage. But this multilayer actuator had some problems. However, due to internal stress around electrodes, crack and delamination were very important issues. Around the edge of conventional inter-digital electrodes, non-uniform electric field generates the stress concentration, which causes the ceramic crack and delamination. The internal stress distribution in multilayer actuator was analysed by a numerical simulation. And by using float electrode, multilayer actuator was manufactured to decrease internal stress concentration of inter-digital electrode. The float electrode could suppress the electric field concentration and cracking in the actuator.

Destruction mechanism in multilayer ceramic actuators has been investigated under cyclic electric fields. Crack propagation has been observed dynamically by using optical microscopy, and the accompanying characteristic of acoustic emission was measured.     

A pi-shaped ultrasonic tweezers concept for manipulation of small particles

A pi-shaped ultrasonic actuator is proposed for the noncontact trapping, extraction, and transportation of small particles. In this actuator, two metal plates clamp a multilayer piezoelectric vibrator by a small bolt, and the metal plates are tapered in their lower parts so that a vibration gradient can be obtained. The flexural vibration of the metal plates is used to generate a sound field in the gap between the two tapered metal plates. At a driving frequency of about 152.8 kHz, shrimp eggs, grass seeds, thyme seeds, rice powder, fine salt, and fine sugar, which have an average diameter from several tens of micrometers to several hundreds of micrometers, can be trapped stably without contact with the actuator, and the particles insoluble in water can be extracted from water and transported in water by the actuator. In the noncontact trapping of small particles, the positions of trapped particles as well as the relationship among the number of trapped particles, vibration velocity, and input power are investigated. The number of trapped particles increases as the vibration velocity or input power increases. However, when the vibration velocity or input power is too large, the particles may be ejected out of the actuator and, therefore, cannot be stably trapped. The minimum vibration velocity to trap small particles increases as particle density increases for the particles that have the shape near to a sphere and a proper density. In the extraction of small particles from water, the relationship between the number of extracted thyme seeds and the input power is investigated. Increasing the input power can increase the extracted thyme seeds. However, there is a maximum particle number that can be extracted from water. In the transportation of thyme seeds in water, the dependence of the particle loss during the transportation on the speed and distance of transportation and the input power is experimentally estimated. As the distance and speed of transportation increase, the particle loss during the transportation increases. Increasing the input power increases the trapping effect and, therefore, decreases the particle loss.     

A multilayer inplane bending piezoelectric actuator for dual-stage head-positioning control system

A novel multilayer in-plane bending piezoelectric actuator, called a multilayer split-morph, was designed and fabricated by thick-film screen-printing technology for a dual-stage head-positioning actuator system in a hard disk drive. The design, operation and theoretical principles have been described. The electromechanical performance of the fabricated actuators has been evaluated. The actuation stroke of the actuator is in inverse proportion to the thickness of the piezoelectric layer. The highest displacement/voltage sensitivity of 0.154µmV^-1 is achieved in a trapezoidal multilayer split-morph with a thickness of 35 m in each piezoelectric layer. The corresponding fundamental resonance frequency of the sway mode is high at 47 kHz in the trapezoid actuator with dimensions of 10.14 mm length, 3.08 mm and 1.54 mm widths of the two parallel sides of the trapezoid. The multilayer split-morph was designed to integrate directly onto a modified suspension load beam. With the combined attractive performances indicated above, the batch fabricated multilayer split-morph can provide a low-cost but promising solution for achieving very high track densities in a hard disk drive by implementing a high performance dual-stage head-positioning actuator system.     

Factors affecting the performance of piezoelectric bending actuators for advanced applications: an overview

The behaviors of piezoelectric bending actuators both in static and dynamic conditions driven by a high electric field were investigated and are summarized in this paper. In the static condition, the polarization and the displacement were measured and analyzed. It was found that the displacement hysteresis loop is the superposition of displacement loop induced by each layer of the actuator. The shape variation of the hysteresis loop is affected by the actuator configuration, i.e., the arrangement of electric field and poling direction. When the poling direction is parallel to an even electric field, such as parallel bimorph, the domain turns to switch at the exact coercive field of the piezoelectric material. However, when the poling direction is antiparallel to the electric field, such as series bimorph, the effect of electric field redistribution will take place during the domain reorientation, which reduces the actual electric field in the electric field–poling direction antiparallel layer, therefore prohibiting further domain reorientation. As a result, the series bimorph is noted to be more resistant to domain reorientation than the parallel bimorph. In the dynamic condition, the functions and relations of vibration velocity, heat generation, stress, and frequency were examined both theoretically and experimentally. It was found that the stress effect dominates at low frequency. At low frequency the failure mode of the actuator is often the physical fracture of the material. However, at high frequency, the failure modes mainly resulted from heat generation, unstable operation, depoling, and domain reorientation of the actuators. The vibration velocity will also decrease accordingly at the high frequency range due to more losses and heat generation.     

Analysis of shaking beam actuator for piezoelectric linear ultrasonic motor

In this paper, piezoelectric linear ultrasonic motors (PLUM) have been investigated on the elliptic trajectory of a contact point in shaking beam, which has been accomplished by two resonance vibration modes of the actuators. The actuators have generated the vibration modes, longitudinal and flexural, by two longitudinal mechanical vibrations with phase difference of pi/2. Modal and harmonic analysis of the shaking beam actuator were performed by the finite element method (FEM) to calculate a resonance frequency and a modal shape and to perform harmonic response. Experimental results proved that a contact point of the PLUM tends to move with an elliptic trajectory.     

Characterization of FGM monomorph actuators fabricated using EPD

Piezoelectric FGM monomorph actuators fabricated using electrophoretic deposition (EPD) were investigated. Both the physical and electromechanical properties were examined. The high voltage performance of the actuator in both static and dynamic state was focused. It was found that the monomorph exhibits tetragonal phase perovskite structure and the gradient variation of microstructure was observed over the cross section. The displacement keeps a wide range of linearity in the static state. In the dynamic state, the vibration displacement is both frequency and voltage dependent. The resonant frequency shifts to lower frequency range due to the higher vibration loss at higher voltages. This results in the frequency dependence of the vibration limitations. The vibration limitation is also voltage dependent. Above a cutoff voltage, the displacement may not increase. To obtain a higher resonant displacement or velocity, the frequency and voltage should match well. Temperature rise or heat generation is caused by vibration loss. The maximum temperature happens at the clamped end of the monomorph.     

晶体结构对压电陶瓷微位移驱动器特性的影响

对钙钛矿结构的ＰＺＴ－５和钨青铜结构的ＰＢＮＮ二种压电陶瓷制成的压电微位移器进行了电压－位移特性的比较和分析，发现我们所研制的ＰＢＮＮ压电微位移器具有线性好、回零好、等优点。     

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     

超磁致伸缩振动器谐振频率自感知机理研究

振动系统工作在谐振频率处则其工作效率最高,但由于受到负载、温度等因素的影响,其谐振频率往往会发生漂移,为了实现对振动系统工作频率的自动调节,提高系统的工作效率,提出采用搜索振动系统速度阻抗的方法,在无需安装检测谐振频率传感器的条件下,实现振动系统谐振工作点的自感知,并能快速、方便地自动跟踪系统的谐振频率。设计了超磁致伸缩振动器,并给出了振动器机械阻抗的表达式;在分析超磁致伸缩材料磁-机耦合关系的基础上,建立了超磁致伸缩振动系统的速度、阻抗及所受外力的自感知模型;在研制的实验系统上,验证了振动系统谐振频率自感知方法的可行性与正确性。     

随机荷载作用下结构主动控制的作动器优化配置

针对实际工程结构在持续的环境干扰下的控制问题,提出一种同时选择其作动器数目、位置和控制增益的次优化配置方法。该方法通过不断地从作动器的可选位置中删除对二次型性能泛函最优值贡献最小的可选位置,并同时调节性能泛函中的控制参数,使结构的响应和控制力同时达到其最大值为止。该方法简单易行,计算效率高,避免了复杂的梯度和成本函数计算,适合于实际工程应用。通过对一个多层剪切型框架进行仿真计算,验证了该方法的有效性。     

多层独石式压电微位移器的扫描电声像研究

对多层独石式压电微位移器的陶瓷／内电极层界面进行扫描电子显微镜（ＳＥＭ）和扫描电声显微镜（ＳＥＡＭ）的无损观察，发现该界面在ＳＥＭ和ＳＥＡＭ观察得到的像所给出的信息存在着很大差别，根据ＳＥＡＭ的成像原理，探针能谱分析（ＥＤＳ）以及器件本身陶瓷／内电极层间的层状结构形式，认为这种差异是由于器件在热压和烧结等制作过程中，陶瓷层和内电极层间不同的收缩率使得界面产生非均匀性力学性能而引起的，它与器件烧结时     

Shock Resistance of a Disk-Drive Assembly Using Piezoelectric Actuators With Passive Damping

Current dual-stage actuator design uses piezoelectric patches only, without passive damping. In this paper, we propose a dual-stage servo system using enhanced active-passive hybrid piezoelectric actuators. Because they incorporate passive damping, the proposed actuators will improve the existing dual-stage actuators, giving them higher precision and better shock resistance. We report finite-element analyses of different types of piezoelectric actuators in a disk arm assembly under external shock and vibration. We modeled the viscoelastic damping layers in the hybrid actuators with the Prony series, whose parameters we determined from the dynamic frequency data of a nomograph. In the analyses, a shock impulse (175 g, 1 ms half sine) and a vibration impulse (350 g and 1 ms full sine) are applied at one end of the base, while the other end of the base is fixed. We evaluated and compared the responses of the disk arm assembly with different configurations of the piezoelectric actuators. The simulation results show that the enhanced active-passive hybrid actuator design would reduce the residual in-plane vibration induced during the shock, resist liftoff motion, and reduce the impact damage when the head slaps.     

磁致伸缩材料作动器在振动主动控制中的应用研究

磁致伸缩材料作动器是一种具有特色的机敏材料作动器。本文在自行研制Ｔｅｒｆｅｎｏｌ－Ｄ作动器及其特性试验的基础上，研究该类作动器在主动隔振与主动吸振中的应用。文中提出并导出了多通道前馈控制的时延滤波—ｘＬＭＳ法，并就这种算法的收敛性进行进一步的讨论。     

DESIGN OF STRUCTURE CONTROL SYSTEM USING BOUNDED LQG

An approach for designing a structure and its control system for vibration suppression is presented. The control system is based on the Linear Quadratic Gaussian (LQG) and is modified to allow bounds on the actuators forces to simulate real actuators. The simultaneous design of the structure and control problem is formulated as a nonlinear optimization problem. The system is designed for minimum weight where the weight includes both the weight of the structure and the weight of the actuators. The weight of an actuator is assumed to be proportional to the bound on the maximum force that it can supply. The design variables include the cross-sectional areas of the structural members and the bounds on the actuator forces. The constraints are imposed on the closed loop frequency distribution and the time to reduce the energy of vibration to a small portion of the initial vibrational energy of the system. The structure is analyzed using a finite element approach. For illustration of the design approach, a truss structure idealized with rod elements is used.     

Composite piezoelectric transducer with truncated conical endcaps“cymbal”

This paper presents original results obtained in the development of the moonie-type transducers for actuator applications. The moonie-type actuators fill the gap between multilayer and bimorph actuators, but its position-dependent displacement and low generative force are unacceptable for certain applications. The moonie transducers were modified systematically by using finite element analysis combined with experimental techniques. A new transducer design, named “cymbal transducer”, was developed with larger displacement, larger generative forces, and more cost-effective manufacturing. The cymbal transducers consist of a cylindrical ceramic element sandwiched between two truncated conical metal endcaps and can be used as both sensors and actuators. The cymbal actuator exhibits almost 40 times higher displacement than the same size of ceramic element. Effective piezoelectric charge coefficient, Eff. d₃₃, of cymbal is roughly 40 times higher than PZT itself     

超磁致伸缩驱动器设计准则的建立

在分析超磁致伸缩材料的工作特性、超磁致伸缩驱动器的基本结构与工作原理的基础上,给出了超磁致伸缩驱动器的设计准则．在所提出的设计准则指导下,开发了用于振动主动控制的超磁致伸缩驱动器,并对其主要特性参数进行了测量．实验结果表明,该驱动器的输出性能达到了设计要求。验证了该设计准则的有效性和实用性．