Showing papers on "Piezoelectric motor published in 1999"

Multilayer piezoelectric motor

Abstract: A method for accelerating or decelerating a moveable body which body is moved by urging a piezoelectric micromotor to the body in a first direction so that a contact region of the piezoelectric motor is pressed to the body and exciting vibrations in the piezoelectric micromotor at the contact region in the first direction and in a second direction along a direction of motion of the body, said vibrations having a first amplitude in the first direction and a second amplitude in the second direction, the method comprising: a) for acceleration, gradually changing a ratio between the second amplitude relative to the first amplitude from substantially zero to a desired non-zero value; or b) for deceleration, gradually changing the ratio between the second amplitude relative to the first amplitude from a non-zero value to substantially zero.

Recent trend of piezoelectric actuator developments

Abstract: In these several years, piezoelectric have become key components in smart actuator/sensor systems such as precision positioners, miniature ultrasonic motors and adaptive mechanical dampers. This paper reviews recent developments of piezoelectric and related ceramic actuators with particular focus on the improvement of actuator materials, device designs and applications.

Piezoelectric transducer and actuator using said piezoelectric transducer

Abstract: A piezoelectric transducer of a new laminated structure is provided that is easy to fabricate, produces a large amount of motive energy and has high mechanical strength. Electrodes are installed on one of the surfaces of respectively a first and a second piezoelectric element formed in a thin shape, a second piezoelectric element formed without an electrode is laminated onto the top of the surface of the first piezoelectric element having an electrode to form a laminated piece. The laminated piece is wound to form a tube or folded to form a rod. The tube or rod-shaped laminate is then baked and polarized to produce a piezoelectric transducer.

Active piezoelectric damper for snow ski or snowboard

Abstract: A board, such as a ski or snowboard, that includes a piezoelectric damper. A sensor such as a piece of piezoelectric material is located on the body of the board such that, as the board vibrates or deforms, the piezoelectric sensor is also deformed. As the piezoelectric sensor deforms, it produces an electrical signal that is provided to a control circuit. The control circuit receives the electrical signal and generates a control signal of proportional amplitude and frequency, but an inverse waveform to the sensed vibration. The control signal causes a piezoelectric damper to stiffen and resist deformation of the board, thus damping the vibration. The sensed signal may also be stored within a memory device and subsequently downloaded to provide a skier profile for analysis.

Piezoelectric stick pointing device

Abstract: A pointing and signaling device for controlling the positioning, movement and operation of a cursor on a display screen that has a single piezoelectric element to indicate movement in three axes. The device generates electrical signals in response to a users force or actuation. The device has an actuator attached to a base. A piezoelectric element is mounted between the actuator and the base for generating electrical signals representative of a magnitude and direction of force applied to the actuator. The piezoelectric element is a shaped as a hollow cylinder. The piezoelectric element includes several conductive traces located on an outer surface of the element and a ground plate located on the inner surface of the element. The conductive plates and the ground plate are connected to a flexible cable by solder.

Precise rotary motor by inchworm motion using dual wrap belts

Abstract: A new type of rotary motor by inchworm motion using two belts is developed. A rotor is wrapped by two opposite belts which are connected to piezoelectric actuators. A serial lever structure with flexure hinges is used to connect a belt and piezoelectric actuators. The lever structure amplifies micro displacement of a piezoelectric actuator. A rotational motion with the step size of 2.36 μrad is obtained through this work. An angular step size can be further reduced by increasing the rotor radius. We present a analysis model of the motor for a design of a similar precise motor.

Stage for charged particle microscopy system

Abstract: A stage assembly for holding a work-piece in a charged particle microscopy system includes a magnetic motor (e.g., brushless linear servo motor) for driving an X-platform riding on a base along the X axis, a non-magnetic linear motor (e.g., piezoelectric motor) for driving a Y-platform riding on the X-platform along the Y axis, and a non-magnetic rotary motor (e.g., piezoelectric motor) for rotating a rotary platform over the Y-platform, wherein the duty cycle of the magnetic motor is substantially greater than the duty cycle of the non-magnetic linear and rotary motors. This along with the particular arrangement of the motors and the platforms yields a compact, durable, and vacuum compatible stage which has minimal mechanical vibrations, minimal interference with the charged particle microscope, minimal particle generation, and high speed area coverage.

Piezoelectric switch with audible feedback

Abstract: A piezoelectric switch comprising an end surface which when pressure is applied, causes a piezoelectric element to switch and generate an electrical signal. In addition, the piezoelectric element provides audible feedback to an operator activating the switch. The piezoelectric switch comprises a plastic housing having the piezoelectric element adhesively attached to an inside surface of a top portion of the housing. Two wires from the piezoelectric element connect to a printed circuit board which is placed adjacent to the piezoelectric element and wires from the printed circuit board extend through a cap for external connections. When the piezoelectric element switches, an output pulse having a predetermined pulse width is generated along with a signal which is fed back to trigger an oscillator connected to the piezoelectric element causing it to buzz, thereby providing audible feedback from the same piezoelectric element.

Method and circuit for driving piezoelectric transformer

Abstract: To provide a piezoelectric transformer drive method and a drive circuit which is capable of preventing breakdown of the piezoelectric transformer due to excessive oscillation on its activation and of obtaining a high efficiency Controller controlling the load power to a constant value is provided The controller is controlled in such a manner that the driving of the piezoelectric transformer is initiated at a frequency higher than the resonating frequency on its activation and thereafter the drive frequency is gradually lowered without passing through the resonating frequency of the piezoelectric transfer on its activation

Development of a linear piezoelectric motor based on the inchworm model

Abstract: The development of a linear transducer type piezoelectric motor is shown. This design utilises theInchworm principle and features a cylindrical device operating inside a metal tube. The motor iscapable of developing high translational forces with macro and micro positioning capabilities. It consists of two cylindrical clamping elements separated by a central driver element which are physically connected but capable of independent operation through three multi-layer actuator stacksconnected to a three channel controller. Inchworm type movement is possible through sequentialactivation of the three elements which allows linear motion along the tube. The prototype motor has undergone a series of static and dynamic tests which demonstrate the successful operation ofthe device. Static tests show that with both clamping elements operating, loadsof up to 45N can be held in place with no overall movement. Dynamic tests show that loads of up to22N can be lifted before clamp slippage becomes a problem. Using 100 volt supply signals and verymodest driving frequencies, translational velocities of up to 4.4 mm/mm have been recorded. Infuture, if the speed of the motor needs to be increased, more powerful amplifiers should be able todrive the motor at higher frequencies and thus greater velocities.Keywords: Inchworm motor, linear motion motor, piezoelectric motor, linear transducer motor.

High-efficiency piezoelectric motor combining continuous rotation with precise control over angular positioning

Abstract: The letter describes a piezoelectric motor that combines the merits of piezoelectric materials, such as high power density generated at electromechanical resonance, and a precise control of displacement. The motor utilizes a direct coupling mechanism between the stator and rotor, where a clutch drives the rotor via locking it. The direct coupling makes it possible to transmit the whole power generated in the piezoelectric element to the rotor, and thus achieve the high efficiency of the motor. It also allows the combining of two regimes of operation: continuous rotation and a stepwise motion within a 360° interval with a high resolution of angular displacement.

Elastic contact problem of the piezoelectric material in the structure of a bolt-clamped Langevin-type transducer

Abstract: Bolt-clamped Langevin-type transducers (BLTs) are widely used in various fields of industrial application of high-power ultrasonics. One of the most crucial points in designing a transducer of this type is estimation of the bearing stress imposed by clamping on the interface between the metal block and the piezoelectric element. This prestress, which compensates for low tensile strength of the piezoelectric materials used, must be larger than the dynamic vibratory stress at the interface between the components in high-amplitude operation. Precise estimation of it is virtually impossible, owing to an intricate elastic contact problem. However, with the use of the unique finite-element-analysis system developed by one of the authors, approximate solutions of the problem have been obtained. A BLT design based on the results of the prestress calculations is proposed. The results of its experimental verification have also been reported.

Novel power circulation methods for a surface acoustic wave motor

Abstract: This paper describes two novel power circulation methods which can increase the efficiency of surface acoustic wave (SAW) motors by 7 times. One method requires two driving interdigital transducers (IDTs) and two unidirectional IDTs to circulate power mechanically in a piezoelectric substrate. Another method requires two unidirectional IDTs and an electrical combiner to circulate power electrically. A traveling wave has been successfully excited at the driving frequency of 14.5 MHz by these two methods. The experimental result shows that the driving performance of the SAW motors with the power circulation methods was equivalent to the conventional non-circulation method. As the input power is one seventh, the efficiency of the SAW motor has been increased by 7 times by using the power circulation methods.

Piezoelectric actuator and fuel-injection apparatus using the actuator

Abstract: A piezoelectric actuator is disclosed, wherein a superposing pulse is generated just after a command pulse falls to thereby reduce oscillations of displacement in piezoelectric elements. In the piezoelectric actuator, an exciting pulse having a preselected pulse width is applied across terminals of the piezoelectric elements to cause strains in dimension for the piezoelectric elements. A pulse is superposed such that it is superposed at a timing a at which the exciting pulse is turned on, and then the exciting pulse is once turned off for a minute length of time, or an interval between b and b', and turned on again at c. The pulse to be superposed is supplied with a timing less than one-fourth a period of an oscillation of the piezoelectric elements. The piezoelectric actuator is effective to prevent the resonance phenomenon and preferably employed for the fuel-injection apparatus.

Piezoelectric actuator, piezoelectric vibrator and portable terminal

Abstract: PROBLEM TO BE SOLVED: To stabilize operation even when a lighter-weight, smaller-sized and/or thinner piezoelectric actuator is used by forming slits between an elastic member and a support member inside the elastic member and elastically vibrating the elastic member in the thickness direction through excitation of the piezoelectric body, in such an actuator. SOLUTION: In this piezoelectric actuator 10, a concentric-disklike piezoelectric body 2 with respect to a disklike elastic body 1 is stuck to a circular setting surface 1d of the upper side of the disklike elastic body 1 in the thickness direction, to form a vibrator 3 consisting of the elastic body 1 and piezoelectric body 2. Also, slits 1a are formed through both the surface and rear of the elastic body 1 between the elastic body 1 and a doughnut-like support 1c on the periphery of the elastic body 1 inside it. Further, the piezoelectric body 2 is stuck to only the circular setting surface 1d, and the setting surface 1d and the doughnut-like support 1c are connected through belt-like beams 1b each having a joining part for joining the beam 1b to the support 1c and another joining part for joining the beam 1b to the setting surface 1d, wherein each of these joining parts is formed so that its thickness is smaller than its width in the radial direction of the setting surface 1d, to amplify excitation of the piezoelectric body 2. Thus, the elastic body 1 is elastically vibrated in the thickness direction of the piezoelectric body 2 by excitation of the piezoelectric body 2.

Piezoelectric sensor device and a method for detecting change in electric constants using the device

Abstract: A piezoelectric sensor device has a piezoelectric body vibrator consisting of the piezoelectric body which is sandwiched by a pair of electrodes, a power source which applies a voltage to the piezoelectric body vibrator so as to get excited for vibration, means for monitoring electric constants to detect changes in electric constants accompanied by vibration of the piezoelectric body. The change in electric constants in the piezoelectric body is detected as a change in frequency for vibration of the piezoelectric body corresponding to an electric constant under the determined conditions. The piezoelectric sensor device has a means to obtain the frequency value from frequencies at not less than two points giving a determined electric constant. According to the piezoelectric sensor device the dispersion in measured values due to change in vibration aptness of vibration system and the polarization state of piezoelectric body vibrator can be made smaller.

Sliding mode control of structural vibrations via active-passive hybrid piezoelectric networks

Abstract: The purpose of this research is to address the issue of nonlinearities in APPN (Active-Passive Hybrid Piezoelectric Networks) based systems. Experimental effort is carried out to quantify the high order nonlinearity and hysteresis in piezoelectric actuation. Based on the sliding mode control theory, a robust controller is developed to compensate for the nonlinearities and uncertainties in the integrated system. The effectiveness of the proposed scheme is demonstrated by a numerical example.

A low-cost piezoelectric motor using a (1,1) non-axisymmetric mode

Abstract: An ultrasonic motor using a (1,1) non-axisymmetric mode has already been described. This motor was intricate and hard to assemble but the mechanical characteristics were promising. A low-cost prototype, based on the same principle, is proposed in this paper. The electromechanical and vibrational behaviour is presented together with the mechanical characteristics of the motor. Finally, some working problems are pointed out and explained.

Thin-plate piezoelectric element, piezoelectric acoustic element formed using the same, piezoelectric vibrator, piezoelectric actuator, piezoelectric transformer, and cold-cathode fluorescent lamp provided therewith

Abstract: PROBLEM TO BE SOLVED: To obtain a thin-plate piezoelectric device which is lessened in thickness so as to be enhanced in device characteristics and reliability, by a method wherein a metal electrode and a piezoelectric material comprised in the thin-plate piezoelectric device are both specified in a relation between Young's modulus and thickness. SOLUTION: The product of the square of Young's modulus and thickness of metal electrodes 2 and 3 comprised in a thin-plate piezoelectric device is set 0.0516 times as large as that of the square of Young's modulus and thickness of a piezoelectric material 1. When the thin-late piezoelectric device is used for a circular piezoelectric acoustic device, the piezoelectric acoustic device is constituted through a manner where a thin-plate piezoelectric device composed of the piezoelectric material 1 as thick as 200 μm or below and the metal electrodes 2 and 3 is bonded to a diaphragm 5 and housed in a resonant case provided with a sounding hole and mesh rear holes. A silver deposited film or a sputtered film is formed as thickness as 2 μm or below, by which the piezoelectric acoustic device of this constitution is increased in sound pressure by 5 dB when an alternating current voltage of 1 V is applied. At this point, a radial electromechanical coupling factor is increased by 5% or so, and a dielectric constant is also increased by 10%. COPYRIGHT: (C)2000,JPO

Laminated piezoelectric element, piezoelectric actuator using the same, piezoelectric sensor and ultrasonic motor

Abstract: PROBLEM TO BE SOLVED: To control a displacement, using a simple control circuit. SOLUTION: This laminated piezoelectric element 100 is formed as an integrated structure, in which a first laminated piezoelectric element 110 and a second piezoelectric element 120 are stacked in the thickness direction. The first laminated piezoelectric element 110 is formed, in such a way that piezoelectric elements 111 which are thinner than piezoelectric elements 121 constituting the second piezoelectric element 120 are laminated. In the first laminated piezoelectric element 110, electrodes 112 are installed between the respective piezoelectric elements 111, and they are electrically connected in parallel at the outside every other layer. In the piezoelectric elements 111, 112, their polarization is treated in the thickness direction. In addition, even in the second laminated piezoelectric element 120, electrodes 122 are installed between the respective piezoelectric elements 121, and they are electrically connected in parallel at the outside every other layer.

Ultrasonic motor and electronic appliance with ultrasonic motor

Abstract: An ultrasonic motor constructed so as to have improved driving force, reduced vibrational loss and smaller dimensions as compared with the conventional art. A piezoelectric vibrator generates a vibrational driving force in response to a received drive signal. A drive signal generator generates the drive signal. The drive signal is transmitted along leads to support members. The support members support, and are in electrical connection with, the piezoelectric vibrator on the substrate. Thus, the support member is effective for both supporting the piezoelectric member and for transmitting the drive signal from the drive signal generator to the piezoelectric vibrator. A moving member is in communication with the piezoelectric vibrator and moves in response to the vibrational driving force. The support member may be comprised of an elastic material so that it is effective for urging the piezoelectric vibrator against the moving member. This increases the frictional relationship between the moving member and the vibrational driving force, thereby increasing the output driving force. The support member may include a relatively thinner constriction portion and a relatively thicker connection portion, the constriction portion being effective for decreasing vibration losses. The support member may also be incorporated as part of the substrate, wherein the substrate includes a recess portion effective for receiving the piezoelectric vibrator to reduce thickness. To further reduce the overall dimensions of the inventive ultrasonic motor, the electrically conductive support member may be part of a drive circuit for generating the drive signal. Also, the support member may be configured for supporting the piezoelectric vibrator at a flex vibration node of the piezoelectric vibrator to reduce vibrational loss.

Method and apparatus for driving piezoelectric motors

Abstract: A method is provided for exciting vibrations in a piezoelectric motor having a plurality of electrode sets, each set comprising at least one first electrode and at least one second electrode between which AC voltages are applied to excite vibrations in the piezoelectric motor, the method comprising: coupling an AC power source to the at least one first electrode and at least one second electrode of a first electrode set; electrically connecting the at least one first electrode to the at least one second electrode of a second set of electrodes with a non-zero impedance that is substantially less than an impedance between them resulting from stray capacitive coupling; and energizing the power source to apply an AC voltage difference between the at least one first electrode and at least one second electrode of the first set of electrodes to excite the vibrations.

Single sided sensor for glide height testing

Abstract: The present invention is a glide height test slider for detecting asperities and irregularities on a surface of a rotating disc. A slider body has a plurality of edges defining its outer boundaries. The slider body has a piezoelectric element on at least one of its surfaces, and the piezoelectric element does not extend outside the outer boundaries of the slider body. First and second confronting conductors are patterned on the piezoelectric element so that an electric field generated by the piezoelectric element in response to a strain force due to vibration of the slider body induces a voltage between the first and second conductors representative of the vibration. The piezoelectric elements may be a separate element bonded to the slider body, or the slider body may be formed of a piezoelectric material to form the piezoelectric element.

Compact Piezoelectric Ultrasonic Motors

Abstract: This paper reviews recent developments of compact ultrasonic motors using piezoelectric resonant vibrations. Following the historical background, ultrasonic motors using the standing and travelling waves are introduced. Driving principles and motor characteristics are explained in comparison with the conventional electromagnetic motors.

Piezoelectric smart structures for noise reduction in a cabin

Abstract: The feasibility of piezoelectric smart structures for cabin noise problem is studied numerically and experimentally. A rectangular enclosure, one side of which is a plate while the other sides are assumed to be rigid, is considered as a cabin. A disk-shaped piezoelectric sensor and actuator are mounted on the plate structure and the sensor signal is returned to the actuator with a negative gain. An optimal design of the piezoelectric structure for active noise control of the cabin is performed. The design variables are the locations and sizes of the disk-shaped piezoelectric actuator and sensor and the actuator gain. To model the enclosure structure, a finite element method based on a combination of three dimensional piezoelectric, flat shell and transition elements is used. For the interior acoustic medium, the theoretical solution of a rectangular cavity in the absence of any elastic structures is used and the coupling effect is included in the finite element equation. The design optimigation is performed at resonance and off-resonance frequencies, with the results showing a remarkable noise reduction in the cavity. An experimental verification of the optimally designed configuration confirms the feasibility of piezoelectric smart structures in resolving cabin noise problems.

Motor mounting for piezoelectric transducer

Abstract: A piezoelectric motor has a piezoelectric transducer disposed within a motor housing. The piezoelectric transducer is constructed of one or more piezoelectric elements, the opposite ends of which are loosely secured within recesses in the interior walls of the motor housing. Electric contact plates disposed on opposite major surfaces of each piezoelectric element hold the center portions of the piezoelectric elements in fixed relationship to each other and provide a means of conducting electical energy to the respective faces of the piezoelectric elements. A moveable piston member is attached to one of the contact plates. When an alternating voltage potential is applied across the major surfaces of the piezoelectric elements, the center portions of each of the piezoelectric elements, as well as the piston attached thereto, reciprocates within the motor housing while the ends of each of the piezoelectric elements remain secured within the recesses in the interior walls of the housing.

Method and apparatus for strain amplification for piezoelectric transducers

Abstract: A method and apparatus for mechanical strain amplification for enhanced piezoelectric transduction. The device consists of a piezoelectric element elevated above the neutral axis of a supporting, micromachined, photoetched substrate by use of castellations on the substrate. By elevating the piezoelectric element above the neutral axis, the charge sensitivity of the device is increased which facilitates the development of high-sensitivity, low-noise transducers. There is a limit to charge sensitivity because the optimal elevation is a function of the physical properties of the supporting structure and the piezoelectric element. Accordingly, a mathematical formulation and finite element analysis (FEA) are provided to define the optimal height of the castellated substrate. The recognition of limits to the castellation height has further led to the discovery of using the relaxor-ferroelectric, single crystal class of materials in the present invention. Because the modulus of these materials is an order of magnitude less than that of piezoelectric ceramics, their use in the method of strain amplification is synergistic due to enhanced piezoelectric coefficients and the ability to extend castellation height. Furthermore, the simplicity of the transducer design, and the fact that its components are selected from photoetched, micromachined parts, result in unprecedented low costs of manufacturing for industrial-grade sensors. This method and apparatus for mechanical strain amplification is integral to a diverse group of piezoelectric-based transducers and sensors, such as accelerometers, velocity sensors, mechanical impedance heads, and hydrophones.

Piezoelectric actuator and electronic apparatus with piezoelectric actuator

Abstract: An ultrasonic motor with an increased driving force is provided. There is provided a bimorph type piezoelectric actuator 1 formed by integrally stacking six piezoelectric elements 11, 12, 13, 14, 15 and 16. The piezoelectric element 12 is thinner than the piezoelectric element 11, and expands and contracts in the same direction as that of the piezoelectric element 11 at the same voltage, and the piezoelectric element 13 is thinner than the piezoelectric element 12, and expands and contracts in the same direction as that of the piezoelectric element 11 at the same voltage. The piezoelectric element 14 contracts and expands oppositely to the piezoelectric element 11 at the same voltage; the piezoelectric element 15 is thinner than the piezoelectric element 14, and contracts and expands in the same direction as that of the piezoelectric element 14 at the same voltage; and the piezoelectric element 16 is thinner than the piezoelectric element 15 and contracts and expands in the same direction as that of the piezoelectric element 14 at the same voltage. Therefore, the expansion and contraction of each of the piezoelectric elements 11, 12, 13, 14, 15 and 16 contribute to a driving force without interfering with the expansion and contraction of the other piezoelectric elements. Since the piezoelectric actuator 1 therefore has a simple structure and has higher output and efficiency than those available in the prior art, its size and power consumption can be smaller compared to those of conventional devices having the same output.

A new linear piezoelectric actuator for low voltage and large displacement applications

Abstract: In this work a piezoelectric actuator is described whose stator is composed of two cylindrical steel axes fitted at the surface of a thin piezoelectric membrane. The slider is a beam pressed in contact with two rotors. Each rotor consists of a cylindrical permanent magnet, pressed in contact with the top surface of each axis, by means of magnetic forces. A travelling wave, at the natural flexural vibration frequency of the thin piezoelectric membrane, is excited via piezoelectric effect. The flexural displacement of the membrane is geometrically amplified by the axes, obtaining a wide precessional motion of the axes. The transmission mechanism of the proposed actuator is based on this motion. The actuator is able to give large displacements with a relatively high linear speed (1.21 m/s) and force (0.51 N) by using a commercial piezoelectric membrane (diameter 32 mm, thickness 0.2 mm), driven at relatively low voltage (±18 V). The very small thickness of the overall structure makes this actuator suitable for microsystem applications. A simple analytical approach of the transmission mechanism is reported and experimental measurements are discussed.