Showing papers on "Piezoelectric motor published in 1993"

Ultrasonic motors

Abstract: An ultrasonic motor is proposed which uses two piezoelectric elements in the stator. One element is used to generate a vibration polarized with respect to the direction of motion of the rotor or the slider. The other one generates a vibration perpendicular to the motion of the rotor. By imaging the ratio of the vibration amplitudes and the phase, the Lissajous figure of the particle on the stator surface can be controlled easily. This makes it possible to operate the motor stably, even at low speed. >

An introduction to ultrasonic motors

Abstract: 1. What is an ultrasonic motor? 2. Theoretical treatment of component elements 3. The Piezoelectric element and vibrator 4. Theory and experiments on the wedge-type motor 5. Theory of the ultrasonic wave motor 6. Equivalent-circuit analysis for the travelling-wave motor 7. Design, assembly and testing of a prototype ultrasonic motor 8. Comparison with electromagnetic motors Autobiographical notes (Toshiiku Sashida) Index

Active suspension systems and components using piezoelectric sensing and actuation devices

Abstract: A lightweight, high performance, active suspension system utilizing piezoelectric regulated springs, and a method of manufacturing the suspension system, is described. Piezoelectric material is bonded to suspension springs, and excited appropriately to vary the stiffness of the suspension system. A method of controlling the stiffness of a spring includes piezoelectric material bonded to the spring, a sensor system for generating a signal proportional to the loading imposed on the spring, and controller for exciting the piezoelectric material in response to the signal. A control system for controlling the stiffness of a spring including embedding a plurality of piezoelectric particles within an electrically conductive matrix forming the body of the spring is also described.

Piezoelectric tubes and tubular composites for actuator and sensor applications

Abstract: Piezoelectric actuators and sensors made with a tubular structure can provide a great agility of effective response in the radial direction. For a radially poled piezoelectric tube, the effective piezoelectric constant in that direction can be tuned to be positive, zero or negative by varying the ratio of the outer radius (Ro) to the inner radius (ro) of the tube. For a suitable ratio of Ro/ro, this effective constant can also be changed in sign or set to zero by adjusting the d.c. bias field level for tubes made of electrostrictive materials. Therefore, one can make a piezoelectric transducer with all the effective piezoelectric tensile constants having the same sign. End-capped thin-walled tubes also exhibit an exceptionally high hydrostatic response, and the small size of the tubular structure makes it very suitable for integration into a 1–3 composite which possesses low acoustic impedance and high hydrostatic response.

Hybrid ultrasonic micromachined motors

Abstract: A hybrid ultrasonic motor has been fabricated using silicon micromachining and metallic micromechanical components. The concept of elastic force motors (EFMs) is applied for the conversion of standing waves to mechanical energy. Millimeter-size prototypes (6*6*2 mm) show interesting characteristics. Free rotation speed up to 600 rpm and net torque of 50 nNm are observed. Typical applications are the motorization of electronic watches or the positioning systems in instrumentation. >

Method and apparatus for testing a piezoelectric force sensor

Abstract: A test system for a piezoelectric element per se or a piezoelectric element in a physical system, which is subject to forces which deform the piezoelectric element, couples an electrical pulse to the piezoelectric element sufficient to stress the element and induce mechanical ringing upon pulse removal. The ringing electrical signal developed by the piezoelectric element characterizes the functionality of the piezoelectric element. A response circuit which is responsive to the ringing electrical signal provides an electrical signal indicative of the functional condition of the piezoelectric element. The electrical signal is peak detected. The peak detected voltage is compared with a reference voltage to provide an indication of the functionality of the piezoelectric element.

Production method of laminated piezoelectric device and polarization method thereof and vibration wave driven motor

Abstract: In one aspect of the present invention, a large number of thin sheets of piezoelectric ceramic are disposed one on another via electrode films formed on the surfaces of the sheets of piezoelectric ceramic, then electrode films of the piezoelectric elements are connected to each other with electric conductors to form a single piece of laminated piezoelectric device Thus, it becomes possible to perform polarization of the whole of a large number of piezoelectric elements at one time

Piezoelectric ultrasonic motor using longitudinal-torsional composite resonance vibration

Abstract: A piezoelectric ultrasonic motor, which uses longitudinal and torsional composite vibration, is examined in order to obtain high torque characteristics with small diameter. Piezoelectric ceramic elements, oscillating in both longitudinal and torsional modes, respectively, are used as piezoelectric stiffened modes having high electromechanical coupling factors k/sub 33/ and k/sub 15/, respectively. It is found that the resonant frequencies for longitudinal mode and torsional mode could coincide with each other in the ultrasonic motor, according to finite element method analysis and experimental measurement. The motor operating in both resonant vibrations indicated good performance. The 20-mm diameter motor exhibited 4 kgfcm maximum torque, 450 r/min maximum rotational speed, 40% maximum efficiency, and quick responsiveness, within 2.5 ms. >

Ultrasonic Rotary Motor Using Longitudinal and Bending Multimode Vibrator with Mode Coupling Caused by External Additional Asymmetry

Abstract: The present paper deals with the ultrasonic rotary motor using a longitudinal and bending multimode vibrator constructed so that the mode coupling is caused by external additional asymmetry. It is well known that on a rectangular piezoelectric plate vibrator with its two corners cut diagonally or a parallelogram-shaped piezoelectric plate vibrator, the first longitudinal and second bending vibration modes are coupled under a certain dimensional condition. The motor mentioned above is to use this phenomenon; that is, a one-channel drive, reversible rotary motor can be achieved. From results of measurement and calculation of such a trial vibrator, it was found that there were two new resonance vibration modes in the neighborhood of degenerate resonance frequencies of original longitudinal and bending vibrations; hence, the directions of rotor revolution were different at both new modes when the mode-coupled vibrator was used to construct an ultrasonic rotary motor. The trial motor has proven that a simple ultrasonic motor could be easily constructed and it was suitable for light-load use because of its small contact area to the rotor.

Piezoelectric force sensor

Abstract: A piezoelectric force sensor is proposed in which a piezoelectric plate (1) has an electrode (4, 5) on the upper side and lower side, respectively One of the electrodes (4, 5) is connected electrically via a conductive track (20, 21) In the event of a breakage of the piezoelectric plate (1), the conductive track (20, 21) is interrupted and the remaining residual capacitance of the conductive track (20, 21) becomes so small that reliable detection of the breakage is possible (Figure 2)

Piezoelectric transformer and method for driving the same

Abstract: A piezoelectric transformer is constituted of a piezoelectric plate in the form of an elongated plate and electrodes formed thereon. A pair of driver sections and a generator section are formed in two opposite end regions of the piezoelectric plate containing a mechanical resonance node and in a central region of the piezoelectric plate containing a mechanical resonance node, respectively, in an oscillation mode of three times of 1/2 of the resonance wavelength λ of the longitudinal mechanical oscillation in length of the piezoelectric plate. The driver sections are polarized in a thickness direction but in directions opposite to each other. The driver sections have a distance of λ/2 from the corresponding end of the piezoelectric plate.

Asymmetric actuation and sensing of a beam using piezoelectric materials

Abstract: The purpose of the present work is the modeling of a beam actuated by a ceramic piezoelectric on the top with a PVDF piezoelectric on the opposite side acting as a sensor The two piezoelectric are different in types, may be of arbitrary length and can be positioned independently along the beam Since there is only one actuator, the asymmetric excitation induces transverse and axial displacement in the beam This asymmetric actuation contrast with the symmetric actuation normally considered in the literature Symmetric actuation implies no axial displacement Here, both piezos are considered perfectly bonded to the beam and the Bernoulli–Euler hypothesis is used for the displacement field The variational approach with Hamilton’s principle is put to use in the theoretical model Hamilton’s principle states that the definite time integral of the Lagrangian shall be stationary This formulation, which is energy based, allows one to consider any boundary conditions and to take into account the dynamic effect

Thermometer for remote temperature measurements

Abstract: An instrument is provided for measuring the temperature of an object from infrared radiation emitted by the object The instrument includes a radiation detector, a temperature indicating device connected to the detector, and a modulator disposed in a path of a radiation beam from the object for converting the beam into a series of pulses when the modulator is vibrated in and out of the path The modulator includes a primary piezoelectric element adapted to vibrate when subjected to driving signals at a frequency related to the resonant frequency of the modulator, and a secondary piezoelectric element connected with and driven by the primary piezoelectric element The secondary piezoelectric element is electrically insulated from the primary piezoelectric element The modulator also includes a blocking element connected with the secondary piezoelectric element and disposed to move in and out of the path of the beam A phase locked loop oscillator circuit is connected to the primary and secondary piezoelectric elements for operating the primary element The secondary piezoelectric element is adapted to generate a signal indicative of the phase and frequency of the primary piezoelectric element to lock the circuit at the resonant frequency of the modulator

Pickup unit for electric string instrument

Abstract: In construction of a pickup unit used for electroacoustic conversion of various vibrations produced on a string instrument, a piezoelectric assembly clamped between a string holder and a bridge is provided with a dual layer arrangement of piezoelectric elements kept in contact with corresponding positive electrodes The piezoelectric elements closer to the string holder detect string vibrations and the piezoelectric elements closer to the bridge detects body vibrations of the string instrument so that electric signals from piezoelectric elements of different groups can be tactfully blended together for rich and voluminous generation of musical tones over a wide tone range

Piezoelectric bimorph type actuator

Abstract: A piezoelectric bimorph type actuator which, given a constant applied voltage, is capable of greater displacement without suffering from the problem of generating a smaller force of displacement or increasing the actuator size. The piezoelectric bimorph type actuator which is cantilevered, includes an electrode plate, a pair of piezoelectric plates provided on both sides of the electrode plate, and a voltage source for applying a voltage between each piezoelectric plate and the electrode plate so as to displace a free end thereof, wherein a ratio t2 /t1 between the thickness t2 of the electrode plate and the thickness t1 of each piezoelectric plate is set to be 0.42-1.11 times as much as a ratio E2 /E1 between the Young's modulus E2 of the electrode plate and the Young's modulus E1 of each piezoelectric plate.

Piezoelectric motor with three-point stator mounting

Abstract: The motor includes a bronze stator (1), which is excited by a piezoelectric transducer, under constant, permanent pressure from one, or two, rotor disks (50,51), covered with low-friction material, which convert its vibrations to rotary motion. The motor is supported in a cylindrical casing (2) by three pegs (4,5), fixed in the median plane (13) of the stator at 120 deg. spacing, and seated in correspondingly spaced elongated openings (10,11) in the casing, with sufficient tolerance to allow rotation.Optionally the pegs may be mounted in ball bearings, or rest in open-topped notches formed on an internal shoulder in the casing. Alternatively, a peripheral shoulder on the stator may have three recesses riding on corresponding projections within the casing.

Impedance-type equivalent circuits of the piezoelectric vibrator for applications to ultrasonic motors and actuators

Abstract: The piezoelectric vibrator has been used at its resonance in general; therefore the equiv-alent circuits have been obtained as an admittance-type expression drawn from the input admittance developed near their resonance point. However, it may not neces-sarily be well for some piezoelectric devices, because they cannot yield a superior char-acteristic when used at the resonance frequency. On the other hand, vibrational char-acteristics of a piezoelectric ceramics vibrator only are proved experimentally to be good at its anti-resonance point. Therefore, the authors thoughthat the equivalent circuit of a piezoelectric vibrator should be expressed depending upon its anti-resonance, where it is called the B-type equivalent circuit. This paper deals with the equivalent circuits developed near the anti-resonance mainly depending upon the input impedance of the piezoelectric vibrator.

Piezoelectric tubes and 1-3-type tubular composites as tunable actuators and sensors

Abstract: Piezoelectric actuators and sensors made of tubular structure can provide a great agility of the effective response in the radial direction. For a radially poled piezoelectric tube, the effective piezoelectric constant in that direction can be tuned to be positive, zero, and negative by varying the ratio of the outer radius (R0) to the inner radius (r0) of the tube. For a suitable ratio of R0/r0, this effective constant can also be changed in sign or set to zero by adjusting the dc bias field level for tubes made of electrostrictive materials. Therefore, one can make a piezoelectric transducer with all the effective piezoelectric tensile constants having the same sign. The end capped thin wall tubes also exhibit exceptionally high hydrostatic response and the small size of the tubular structure makes it very suitable for integration into 1 - 3 composite which possesses low acoustic impedance and high hydrostatic response.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Ultrasonic motor unit

Abstract: An ultrasonic motor unit comprises a stator having a piezoelectric member and an elastic member which is excited by the piezoelectric member to generate a travelling vibration wave, and a rotor which is press-contacted to the stator and driven by the travelling vibration wave. At least two sets of input electrodes each having two input electrodes are circumferentially arranged on the piezoelectric member. A drive voltage is applied to only the selected ones of the input electrodes in accordance with a drive power requirement.

Characteristics of a Bidirectional Rotary Ultrasonic Motor Using Obliquely Polarized Piezoelectric Transducers

Abstract: Obliquely polarized piezoelectric ceramic transducers are newly employed to an ultrasonic motor. Since the direction of polarization is neither parallel nor perpendicular to the applied electric field, the longitudinal and the torsional vibrations are excited simultaneously. In addition, the direction of rotation can be switched by changing the driving frequency. Thus, this motor rotates in both clockwise and counterclockwise directions in spite of a single-phase input signal. The principle and the characteristics of the ultrasonic motor are described.

Scanning tunneling microscope‐based nanostructure fabrication system*

Abstract: We have designed a novel scanning tunneling microscope (STM) and control electronics system to investigate STM‐based nanostructure fabrication on semiconductor surfaces. Several elements of our design are unique to this application. The STM, which resides in a vacuum chamber, can be positioned anywhere on a 1 cm×1 cm sample. This is accomplished by using three piezoelectric motors (Burleigh Inchworms) and locating the tip position with a long working distance optical microscope (Questar). One piezoelectric motor is used for the coarse Z approach while the other two adjust the X,Y tip position. The tip is attached to a tube‐type piezoelectric scanner. The piezo tube’s x–y scan range is 12 μm×12 μm. The tube’s mechanical and electrical response are linear to 6 kHz and allow rapid scanning. Both tip and sample are attached to the microscope magnetically to facilitate rapid self‐aligned exchange under vacuum. A computer controlled pattern generation system allows arbitrary patterns to be drawn on the sample. ...

Piezoelectric switching element

Abstract: A piezoelectric switching element exhibits a carrier-like housing 3 on or in which a piezoelectric element 5 in the form of a piezoelectric disc is arranged. At the two mutually opposite electric connecting poles 11', 11'' of the piezoelectric element 5, contact is made to an electric circuit 12, the connections being located on a common side. This electronic circuit 12 is used for processing the voltage pulse output by the piezoelectric element 5. For the simple and reliable production of the piezoelectric switching element, a flexible electric conducting element is provided which is brought into contact with the one electric connecting pole 11'' of the piezoelectric element 5 and is bent back by 180 DEG to the opposite side of the piezoelectric element 5 around the piezoelectric element 5 in such a manner that the electric conducting element is located on the same side as the piezoelectric element 5 as the connection of the other electric connecting pole 11'.

Plane ultrasonic piezoelectric actuators

Abstract: Two prototypes of plane ultrasonic piezoelectric actuators were experimentally constructed, and the fundamental characteristics were measured. The vibration mode of actuators was also analyzed by ANSYS, and compared with the experimental results. An ultrasonic piezoelectric actuator has the advantage of compactness and standstill force without excitation. >

Study of smart-sensing elements in a dynamic stress field

Abstract: The desire to counteract impact loads on laminated structures in order to reduce ply damage has recently led to research using smart materials in laminated composites. The ability to sense the onset of these impact loads using piezoelectric material is the first step in the damage control process. This research focuses on smart laminated plates under impact and the electric field created by piezoelectric patches in the structure. A modified version of an existing finite element program is used to numerically simulate a laminated plate under a low velocity impact. Linear constitutive relations are used in the program which calculate the electric field generated by the in-plane strains on the piezoelectric plies. Several studies are made comparing the electric field generated by patches of piezoelectric material of varying size, shape, and location within the plate. The average electric field generated by larger patches which contain more oscillations of electric field filters the high frequency components. The distance between the impacting point and the piezoelectric sensor is found to be directly related to the lag time between the impact and generation of an electric field.

Drive circuit of piezoelectric vibrator

Abstract: PURPOSE:To always drive a piezoelectric vibrator used in a piezoelectric motor or the like at constant amplitude. CONSTITUTION:In a pulse width modulating part A, the oscillation output with predetermined frequency from an oscillation part 15 is modulated in its pulse width by the control power obtained from a CPU 25 through a D/A conversion part 26 and the vibrator 2 for twist vibration and vibrator 4 for longitudinal vibration of a piezoelectric motor 10 are driven by this driving power to rotate a rotor 6. The power based on the amplitude difference of the piezoelectric vibrator 2 is taken out by the bridge circuit of a vibration detecting part F to be negatively fed back to a differential amplifier 18 to obtain pulse width modulating control power E1. By modulating pulse width by the power E1, the vibrator 2 is always driven at constant amplitude and the motor can be driven in the constant number of rotations.

Process for producing vibrator for piezoelectric motor

Abstract: A vibrator for a piezoelectric motor is produced by forming an elastic material into a predetermined shape, forming a piezoelectric material on the shaped elastic material for polarization and for driving, forming an electrode for polarization on the piezoelectric material, forming an electrode for driving on the surface of the electrode for polarization or on the piezoelectric material after stripping the electrode for polarization, and etching the elastic material into a predetermined shape has an elastic body and to remove the elastic body from a base. Instead of forming the piezoelectric material on the shaped elastic material for polarization and for driving, an electrode both for polarization and for driving can be formed on one face of the shaped elastic material, and the piezoelectric material can be formed on that electrode.

Piezoelectric force and torque measurement transducer - contains two or more piezoelectric elements in modulator contg. plate acting on piezoelectric elements, summing amplifier for output voltages

Abstract: The measurement transducer contains at least two piezoelectric measurement elements (20). A calibrated output force converted from the measurement force or torque by a transducer acts periodically with a carrier frequency on a plate (18) coupled mechanically to the piezoelectric measurement elements in a piezoelectric modulator (11). Voltages in the measurement elements amplitude modulated with the carrier frequency are summed in a summing amplifier to form a measurement value directly proportional to the output force. USE/ADVANTAGE - Satisfactory static and dynamic force and torque measurements are achieved without the use of charge amplifiers and with high mechanical stiffness and overload protection.