Showing papers on "Piezoelectric motor published in 1995"

Modeling of a piezoelectric rotary ultrasonic motor

Abstract: A piezoelectric rotary ultrasonic motor is modeled for the purpose of predicting, a priori, motor performance as a function of design parameters. The Rayleigh-Ritz assumed mode energy method is used to model the distributed piezoceramics and the traveling wave dynamics of the stator. Natural frequencies and modeshapes are obtained for a generally configured motor. Nonlinear normal and tangential interface forces between the rotor and stator are incorporated into the forcing function along with the linear piezoelectric forcing. Given the applied torque, applied axial loading, and piezo drive voltages as inputs to the model, general motor performance measures are obtained-namely speed, input power, output power, and efficiency. The approach presented here provides a general framework for modeling these motors as well as a design tool for optimizing prototypes with the added flexibility of allowing for a wide variety of geometries and materials. >

Modeling of a three-layer piezoelectric bimorph beam with hysteresis

Abstract: Piezoelectric actuators are usually stacked or bimorph in configuration. In this paper the mechanics of a three-layer piezoelectric bimorph is discussed and its dynamic model with hysteresis is presented. The results can be used to analyze piezoelectric actuators constructed with three-layer piezoelectric bimorphs. A piezoelectric bimorph actuator has been fabricated and experiments have been carried out to verify the model. The calculated results of this model closely matched the tested results. This model can also be used with other types of piezoelectric actuators with a slight modification.

Piezoelectric ultrasonic motors

Abstract: Piezoelectric ultrasonic motors are a new type of actuator. They are characterized by high torque at low rotational speed, simple mechanical design and good controllability. They also provide a high holding torque even if no power is applied. Compared to electromagnetic actuators the torque per volume ratio of piezoelectric ultrasonic motors can be higher by an order of magnitude. Recently various types of piezoelectric ultrasonic motors have been developed for industrial applications such as cameralens drive or as actuator in the head restraint of automobile seats. This paper describes several types of piezoelectric ultrasonic motors. In the first part the working principle of the travelling wave motor is explained. In the second part other types of piezoelectric ultrasonic motors are described and classified with respect to the vibration modes and contact mechanisms used in their design. Finally some open problems in piezoelectric ultrasonic motor research are addressed.

Stiff actuator active vibration isolation system

Abstract: An active vibration isolation system (10) includes a plurality of stiff actuators, such as piezoelectric motors (12a-c; 284, 350) which support a small mass (18) inside of a case (300). A passive isolator (20) is interposed between the small mass (18) and the payload mass (Mp). In the instance where the stiff actuators are piezoelectric motors, the sidewalls of the case (300) are used to provide compressive force along the variable length of each of the horizontal piezoelectric motor elements (284, 350) to prevent damage to same. Compensation circuitry (24) is connected between velocity sensors (17) and the stiff actuators to control the variable length thereof in this move-out-of-the-way system (10) and to compensate for resonating modes. Optionally, a payload mass velocity sensor (26) and associated circuitry may be used to provide additional control. Shear decouplers (282a-c; 352, 360) are used in conjunction with the piezoelectric motor elements (12a-c; 284, 350) to minimize the amount of shear force acting on the motor elements.

A micropositioning device for precision automatic assembly using impact force of piezoelectric elements

Abstract: A micropositioning system for automatic precision assembly is introduced. The proposed precision assembly system is aimed at automation of precision assembly of precision optical or magnetic components, which was previously performed by specially trained technicians. The positioning system is based on the motion mechanism driven by impact force made by piezoelectric actuator; it utilizes dry friction and impulsive inertial force. The motion mechanism consists of the main body, a piezoelectric actuator, and a weight. The motion mechanism can make minute motion of several nanometer and has an unlimited movable range at the same time. The proposed assembly system uses the motion mechanism as a source of impact force. The motion mechanism is proved to have the advantage of positioning resolution, range, and flexibility. An industrial application of this device is also presented.

Ultrasonic Linear Motor Using Multilayer Piezoelectric Actuators

Abstract: In order to lower operating voltage and improve the lifetime of an ultrasonic linear motor, we have developed an ultrasonic oscillator with multilayer piezoelectric actuators. Multilayer piezoelectric actuators are operable at low voltage. However, the tensile strength of the multilayer piezoelectric actuator is small. Therefore, the multilayer piezoelectric actuators are build within an elastic body to lower the tensile stress with a compressive preload. Elliptical oscillations are generated by synthesizing two degenerated modes, a first longitudinal mode and a second flexural mode, with π/2 phase difference. As a result of estimating the characteristics of the ultrasonic linear motor with the ultrasonic oscillator, the operating voltage of 10 Vp-p, maximum thrust force of 8 N and lifetime of over 5000 hours have been obtained.

Thermally induced vibration suppression of laminated plates with piezoelectric sensors and actuators

Abstract: A finite-element model is developed for the active control of thermally induced vibration of laminated composite plates with piezoelectric sensors and actuators. The present model takes into account the mass, stiffness and thermal expansion of the piezoelectric patches. A C0 continuous nine-noded shear flexible element is implemented to model the plate. The piezoelectric sensing layer monitors the structural oscillation due to the direct piezoelectric effect and the actuator suppresses the oscillation via the converse piezoelectric effect. These two effects are then coupled with a constant gain feedback control algorithm to actively control the dynamic response of the plate in a closed loop. Numerical results indicate that thermally induced deformation of a laminated plate can be suppressed through the application of electrical potential to the piezoelectric patches.

Piezoelectric loudspeaker and a method for manufacturing the same

Abstract: Disclosed is a piezoelectric loudspeaker. According to the present invention, a piezoelectric loudspeaker comprises: a flat compound piezoelectric sheet in which multiple piezoelectric devices are arranged in an organic material; electrodes which are provided on respective surfaces of the compound piezoelectric sheet; an acoustic impedance matching support layer for maintaining the flat compound piezoelectric sheet in a curved shape and for matching an acoustic impedance; and a support frame for supporting the compound piezoelectric sheet at its circumference. Thus, sound reproduction with a desirable frequency properties that have little distortion can be performed.

Ultrasonic medical treatment apparatus

Abstract: An applicator includes a concave piezoelectric oscillator. The concave piezoelectric oscillator comprises a plurality of piezoelectric oscillation plates having equal areas. Each piezoelectric oscillation plate comprises a plurality of piezoelectric oscillator elements. Each piezoelectric oscillator element has a higher resonance frequency in the lateral direction thereof than in the thickness direction thereof.

Piezoelectric rotation driving apparatus

Abstract: The present invention provides a piezoelectric rotation driving apparatus wherein the number of the piezoelectric driving bodies is reduced so as to miniaturize the size of the apparatus. Furthermore, the apparatus is capable of achieving a high efficiency and a high torque by extinguishing an inertia rotation period. A set of the piezoelectric driving bodies (18,20) including stacked piezoelectric elements are pressed against a cylindrical rotation body (12) serving as a rotor, which is fitted to a rotation shaft, with leaf springs. The piezoelectric driving bodies are combined integrally with each other by a fitting pin such that action direction of forces of action members in the piezoelectric driving bodies driven by the stacked piezoelectric elements are inverse.

Piezoelectric Ultrasonic Micromotors

Abstract: This report describes development of micro-fabricated piezoelectric ultrasonic motors and bulk-ceramic piezoelectric ultrasonic motors. Ultrasonic motors offer the advantage of low speed, high torque operation without the need for gears. They can be made compact and lightweight and provide a holding torque in the absence of applied power, due to the traveling wave frictional coupling mechanism between the rotor and the stator. This report covers modeling, simulation, fabrication and testing of ultrasonic motors. Design of experiments methods were also utilized to find optimal motor parameters. A suite of 8 mm diameter x 3 mm tall motors were machined for these studies and maximum stall torques as large as 10^(- 3) Nm, maximum no-load speeds of 1710 rpm and peak power outputs of 27 mW were realized. Aditionally, this report describes the implementation of a microfabricated ultrasonic motor using thin-film lead zirconate titanate. In a joint project with the Pennsylvania State University Materials Research Laboratory and MIT Lincoln Laboratory, 2 mm and 5 mm diameter stator structures were fabricated on 1 micron thick silicon nitride membranes. Small glass lenses placed down on top spun at 100-300 rpm with 4 V excitation at 90 kHz. The large power densities and stall torques of these piezoelectric ultrasonic motors offer tremendous promis for integrated machines: complete intelligent, electro-mechanical autonomous systems mass-produced in a single fabrication process.

Piezoelectric loudspeaker and method for manufacturing the same

Abstract: Disclosed is a piezoelectric loudspeaker. According to the present invention, a piezoelectric loudspeaker (2) comprises a flat compound piezoelectric sheet (4) in which multiple piezoelectric devices (14) are arranged in an organic material (16); electrodes (6A, 6B) which are provided on respective surfaces of the compound piezoelectric sheet (4); an acoustic impedance matching support layer (8) for maintaining the flat compound piezoelectric sheet (4) in a curved shape and for matching an acoustic impedance; and a support frame (10) for supporting the compound piezoelectric sheet (4) at its circumference. Thus, sound reproduction with a desirable frequency properties that have little distortion can be performed.

Vibration type motor device

Abstract: A vibration type motor device excites a vibration member by applying frequency signals to piezoelectric elements so as to obtain a driving force. A vibration state detection piezoelectric element is arranged on the vibration member, and when a vibration state is determined by detecting the phase difference between the output from the detection piezoelectric element and a driving frequency signal, a predetermined signal is superposed on the output from the detection piezoelectric element, thus allowing accurate detection of the vibration state even when the output from the piezoelectric element includes noise.

Multilayer Piezoelectric Motor Using the First Longitudinal and the Second Bending Vibrations

Abstract: A piezoelectric linear motor using a double-mode vibrator was constructed with one of the vibration modes being the first longitudinal and the other, the second bending. In order to reduce driving voltage, a multilayer piezoelectric ceramics vibrator prepared by a cofiring method was used. Moreover, we proposed a new type of supportive mount for the vibrator to facilitate the construction of the motor. In the new method the vibrator is bonded to an attachment plate by an elastic layer. In this paper, characteristics of the motor are described.

Piezoelectric generator protection

Abstract: A known type of piezoelectric power generating system for converting the mechanical energy of waves on a body of water comprises a float and a piezoelectric power generating element suspended, under tension, between the float and a bottom anchor. For preventing excessive vertical stretching of the piezoelectric element in response to the presence of excessively high waves, a protective element is coupled between the float and the bottom anchor for effectively limiting the rise of the float above a preselected height corresponding to the maximum straining desired for the piezoelectric element. The coupling is automatic and occurs only at those instances when the piezoelectric element elongation is approaching its maximum amount, and automatic decoupling occurs immediately upon the float falling to a height where non-excessive straining occurs.

Hybrid piezoelectric for ultrasonic probes

Abstract: An ultrasonic probe for coupling acoustic signals between the probe and a medium is provided. The ultrasonic probe has a piezoelectric element having a plurality of piezoelectric layers each having a different acoustic impedance. The piezoelectric layers are stacked in progressive order of acoustic impedance such that the layer with the acoustic impedance nearest to that of the medium is proximate the medium. At least one of said piezoelectric layers is made of piezoelectric composite material. The ultrasonic probe further has an electrode means for electrically coupling the piezoelectric layers to a voltage source for applying an oscillation voltage potential to each piezoelectric layer. The probe further has a control means for controlling the polarization of at least one of the piezoelectric layers.

Development of a Flexure-Hinged Translation Mechanism Driven by Two Piezoelectric Stacks

Abstract: This paper describes a monolithically constructed, flexure-hinged translation mechanism suitable for mechanical scanning stages of very high precision. Two piezoelectric stacks are employed to drive the mechanism ; one piezoelectric stack pushes whilst the other pulls the moving platform. This push-pull drive system is effective for raising the natural frequency of the stage. The mechanism described in this paper functions as both a guide for rectilinear motion and a mechanical amplifier to amplify a limited output displacement of the piezoelectric stack. Static and dynamic characteristics of the mechanism are considered in detail, and design equations are presented. The validity of the design equations is confirmed by experiment. A brief description of the accuracy of motion of the moving platform is included. It is demonstrated that a scan range of 60 μm is achievable with a natural frequency as high as 1175 Hz in the scanning direction.

A new type of linear piezoelectric stepper motor

Abstract: A new type of linear piezoelectric stepper motor combining the piezoelectric effect with the electrorheological (ER) effect as studied. The ER effect occurred in fluids that can make a transition from the liquid state to a weak solid state reversibly controlled by an electric field. The driving device of a piezomotor consists of a bilayer piezoactuator using PMN-PNN-PZT ceramics, an ER fluid clamp, and a grid base. Compared with conventional piezoelectric motors, it has unique advantages: no vibration noise, zero wear, low power consumption, large travel range, high mechanical resolution, etc. It will be used widely in the field of precise micropositioners particularly, such as STM, alignment of optical fibers, biological cell operation, and semiconductor manufacture techniques, etc. A motor with an inchworm velocity of about 1.5 /spl mu/m/s and pulse force of about 0.25 kgf was obtained. >

Window raising device

Abstract: An even plurality of piezoelectric motor units operating directly on an element to be vertically translated, such as a car window, is disclosed Each pair of piezoelectric motor units are located along an horizontal line on opposing sides of the element The piezoelectric motors are preferably, asynchronously operated An activation system for providing alternating current (AC) voltage to each of the piezoelectric motor units and converting direct current voltage to a sinusoidal square wave, is also included

Ultrasonic piezoelectric transducer and ultrasonic actuator

Abstract: An ultrasonic piezoelectric transducer and an ultrasonic actuator for performing enhanced elliptical vibration comprise a first laminated piezoelectric element having a first fixed end, a resonator mounted to the opposite end of the first laminated piezoelectric element, a second laminated piezoelectric element having one end thereof fixedly mounted to the resonator in a direction other than a vibrating direction of the first laminated piezoelectric element, and a load mass fixedly mounted to the opposite end of the second laminated piezoelectric element. This structure permits the enhanced elliptical vibration of the transducer to have a large, controllable amplitude.

Pushy motors (piezoelectric motors)

Abstract: A motor using a piezoelectric instead of electromagnetic driving mechanism gives very high torque at low speeds and allows very precise positioning. The author describes the operating principles of piezoelectric motors using PZT ceramics. The design of the motors is then described. The design of the travelling wave motor to overcome the unidirectional problem of piezoelectric motors is described. The main features, advantages and drawbacks of piezoelectric motors are discussed.

Piezoelectric element and piezoelectric actuator using it

Abstract: PURPOSE: To provide a low-cost moisture-proof piezoelectric element in which internal stress is eliminated to prevent cracking. CONSTITUTION: In a piezoelectric element, an internal electrode 4 is formed estranging a specific space D from the end side 2A on a surface of a piezoelectric seat 2, whereby piezoelectric element plates 21 provided with a piezoelectric inactive region 24 are formed and a plurality of piezoelectric element plates are stacked. A shrinkage ratio adjustment thin film 28 is formed in the piezoelectric inactive region of the piezoelectric element plates. Thus, shrinkage states of the piezoelectric seats in the piezoelectric inactive region and piezoelectric active region are approximately the same and a generation of an internal stress is suppressed to prevent a generation of cracks, etc.

Piezoelectric motor unit

Abstract: An even plurality of piezoelectric motor units (36a,36b) operating directly on an element to be vertically translated, such as a car window (32), is disclosed. Each pair of piezoelectric motor units (36a,36b) are located along an horizontal line on opposing sides of the element (32). The piezoelectric motors (36a,36b) are preferably, asynchronously operated. An activation system for providing alternating current (AC) voltage to each of the piezoelectric motor units (36a,36b) and converting direct current voltage to a sinusoidal square wave, is also included.

Development of a rotary inchworm piezoelectric motor

Abstract: The development of a rotary inchworm-motor using piezoelectric actuators is presented. The motor design has the advantage of a macro and micro stepper motor with high torque and speed. The design is capable of fast angular positioning with micro level accuracy. The rotary motor, as designed, can also be used as a clutch/brake mechanism. A constructed prototype motor along with its characteristics are presented. The motor consists of a torsional section that provides angular displacement and torque, and two alternating clamping sections which provide the holding force. The motor relies on the principal piezoelectric coupling coefficient (d33) with no torsional piezoelectric elements used. The design eliminates bending moment and shear applied to the actuator elements, increasing its torque capability. An innovative flexure design has been introduced, and consideration has been given to contact elements which affect the performance of the motor; these issues are explored and discussed. Experiments are performed demonstrating a motor prototype based on the aforementioned design considerations.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Piezoelectric vibrator for ultrasonic wave motor, production method thereof, method of mounting piezoelectric vibrator and ultrasonic wave motor

Abstract: The piezoelectric vibrator for ultrasonic motors of the present invention is one capable of causing a piezoelectric vibrator component to generate a longitudinal vibration/bending vibration to thereby drive a moving element, said piezoelectric vibrator comprises a piezoelectric vibrator component and, bonded thereto through an elastic member, either a mounting member having means for bonding with a fixture or a fixture. This piezoelectric vibrator for ultrasonic motors is free from lowering the resonance characteristics of the piezoelectric vibrator component and enables operating the ultrasonic motor in high efficiency. Further, the assembly of the piezoelectric vibrator into the ultrasonic motor can be effected more easily and more securely than in the prior art and the stability and reliability thereof can markedly be improved at the time of motor operation. The ultrasonic motor of the present invention is an ultrasonic motor of the standing-wave type comprising a piezoelectric vibrator provided with a wear resisting member at its face opposite to a driving surface in the vicinity of an end thereof in the driving direction and bonded with a magnet for pressurizing the piezoelectric vibrator against the driving surface composed of a magnetic material by means of a bonding material, said magnet being disposed apart from the driving surface. This ultrasonic motor attains not only simplification of the pressurization mechanism and miniaturization of the motor and further ensures high driving efficiency.

Multi-cycle electric motor system

Abstract: The active elements of magnetostrictive and piezoelectric actuators undergoyclic elongation and contraction in out-of-phase relation to each other when energized by the same electric power supply to exert push/pull forces during four cycle phases of an operational sequence to impart continuous, unidirectional propulsion to a driven member.

Piezomotors using flexure hinged displacement amplifiers

Abstract: The design and construction of two different piezomotors developed by the authors is briefly described. Both employ flexure hinged mechanical displacement amplifiers to increase the output movement of stack-type piezoelectric actuators to enable them to be applied to rotation generating mechanisms. The first example is a harmonic piezomotor. The harmonic drive principle enables the production of an externally commutated motor which can be driven as a conventional stepping motor for open-loop applications and which yields a very fine rotational increment. The use of piezoelectric actuators makes the motor power consumption almost zero in holding situations, which gives it an advantage over conventional electromagnetic motors in some applications. The second prototype piezomotor presented is based on a roller clutch mechanism. Using one, or more, piezo-stack actuators and a roller clutch as the rotational motion converter, this motor has a very simple structure and requires only a single phase power input. To achieve effective movement of the motor using commercial tolerance roller clutches, the output movement of the piezo-stacks is again magnified by flexure hinged displacement amplifiers. (5 pages)

An Electromagnetic Cycloid Motor.

Abstract: A piezoelectric cycloid motor, which was proposed in a previous paper, is composed of an internal and external gear pair and four drive units containing piezoelectric actuators. The motor has hence some merits which arise from gear drive: no slip motion, long life, and precise motion. It has moreover an excellent characteristics that it rotates steadily and keeps its rotational speed up to its maximum output torque at any rotational speed. The efficiency increases as the rotational speed and the load increase. The motor, however, is subject to a drawback in that it is very difficult to miniaturize because the motor requires four magnifying lever mechanisms to increase the very small displacement, l0μm, of a piezoelectric actuator. In this paper, an electromagnetic cycloid motor is proposed, which is directly driven by four electromagnetic linear actuators instead of the four drive units. The motor rotates based on the same principle as the piezoelectric cycloid motor, but is not subject to the drawback. The output characteristics are experimentally and theoretically investigated.

Piezoelectric motor having an arrangement which provides information relative to the rotor position and/or the rotor's number of revolutions

Abstract: Along the inner lying rotor trailing surface (21) of an annular rotor (20) are successively provided regions (26a-c) of small wall thicknesses (29) and regions (25a-c) of larger wall thicknesses, which differ with respect to the acoustic impedance spectrum. During the state of operation, i.e. when the rotor (20) turns, the mentioned regions (24a-c; 25a-c) are excited alternately by the piezoelectric excitor (15) of the stator (13). The acoustic impedance spectrum which changes periodically, influences the electrical impedance spectrum of the motor (10) in an analog manner. These changes are measured via the voltage supply connections of the motor (10) and are interpreted as relative positional changes between the stator (13) and the rotor (20).