Showing papers on "Bimorph published in 1995"

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.

Compact active/adaptive x‐ray mirror: Bimorph piezoelectric flexible mirror

Abstract: A very compact active x‐ray mirror based on the properties of bimorph piezoelectric systems has been developed at the ESRF. The use of such a system as an x‐ray focusing device has a number of advantages among which are compactness, low cost, and versatility. As a demonstrative test, a white focused beam of 35 μm has been obtained on an ESRF bending magnet beamline that corresponds to a demagnification of 1/18. A theoretical description of the system behavior is given, and compared with both finite element analysis and interferometric measurements. Examples of more advanced devices are discussed.

Thermally actuated CMOS micromirrors

Abstract: Thermally actuated micromirrors fabricated using a standard CMOS process and one subsequent anisotropic silicon etch step are presented. The device consists of a mirror plate supported by bimorph cantilever beams. Even short beams show a large deflection effect. A theoretical analysis valid for n-morph bending beams has been derived and found to be consistent with experimental and computer-simulation results.

Design, Fabrication, And Testing Of A C-shape Actuator

Abstract: SUMMARY This paper describes the design, fabrication, and testing of a microactuator, whose bimorph beams curl up to form a C-shape and reach hundreds of microns from the substrate. The multi-layer C-shape beams were designed by FEM nonlinear analysis and fabricated on a silicon wafer by surface micromachining involving polyimide and metal thin films. The large curvature (i.e., small radius of curvature) is achieved by utilizing the large residual stress difference between thin films. The device is normally curled up, and it opens up by either electrostatic or thermal actuation. The device was operated successfully in liquid as well as in air to their full range between complete curl up and flat positions, demonstrating tip displacements of over two hundred microns.

Soft-handling gripper driven by piezoceramic bimorph strips

Abstract: This paper is a study on the hybrid position/force control of a two-fingered miniature gripper driven by piezoelectric bimoph cells. The system is composed of the flexible cantilevers and a compact force sensor attached to the tip of one finger. Control action is applied by two piezoelectric bimorph strips placed at the base of each finger. The theoretical model of the electro-mechanical system is developed and applied to the study of a control problem where the gripper is commanded to grasp its object with a time-constant force 0.01 N at a prescribed commanded fingertip position. The PID control algorithm is introduced to drive the gripper.The system control behaviour is examined both theoretically and experimentally.

Piezoelectric Cantilever Beams Actuated By PZT Sol-gel Thin Film

Abstract: Micromachined silicon cantilever beams actuated by the converse piezoelectric effect are of great interest for actuator applications [1], and for the characterization of piezoelectric thin films [2]. In this work a study of the mechanical response of piezoelectrically operated heterogeneous bimorph structures is given and compared with finite elements simulations. Determination of the piezoelectric parameter d/sub 31/ using interferometric displacement measurements, electrical impedance measurements, and finite element calculation will be discussed.

2-dimensional optical scanner applying a torsional resonator with 2 degrees of freedom

Abstract: A two-dimensional optical scanner suitable for integration in a plane structure has been developed. To make it vibration robust, a torsional vibration system with two degrees of freedom is adopted for the resonator, and the vibration system axis is matched to the center of gravity. Bimorph cells are used as the actuator to excite the torsional vibration. This optical scanner is capable of optical scanning in two orthogonal directions independently or simultaneously at a scanning angle of +30 degrees or more. One-dimensional scanning is enabled by driving the bimorph cells with the resonance frequency of either of the two torsional vibrations. Two-dimensional scanning is achieved if the bimorph cells are operated by adding the resonance frequency signals of the two torsional vibrations.

Performance improvement of optical actuator by double side irradiation

Abstract: This study is intended to improve the photoresponse of an optical actuator with a bimorph PLZT element. Known optical actuators have multiple merits for converting light energy to driving energy but have a slow response speed and large hysteresis. A method developed by us for exposing both sides of the bimorph element to light has been proved through a series of experiments that the response speed is increased and the hysteresis is reduced thus improving the photoresponse. More particularly, an optical servo system was fabricated for implementing the method and subjected to optical servo tests with PI control. As a result, the PI control was performed with much ease when both sides of the bimorph PLZT were irradiated indicating an advantage of the method. >

Excimer laser ablation of PZT thin films on silicon cantilever beams

Abstract: Laser ablation was used to realise piezoelectric films for use in a low-voltage cantilever bimorph actuator structure Neodymium-doped lead zirconium titanate (PZT) targets were ablated by a pulsed XeCl excimer laser (wavelength 308 nm) The deposited films showed a better morphology than those ablated using a Nd:YAG laser Since the deposited films had high density and small particulate size it was possible to produce a capacitor structure without causing short circuits during the second electrode deposition The depositions were made onto the inner electrode layer on the silicon substrates (thickness 50 μm) at a distance of 20 mm between substrate and target using a laser beam fluence of 1 J/cm2 Growth rates were typically 3 A/s Films were analysed by EDS, XRD and Raman measurements Both the target density and the beam intensity were important in determining the film composition The as-deposited PZT films were amorphous Optimising the annealing conditions resulted in trigonal perovskite being achieved as the main phase Direct current bending characteristics of the low-voltage bimorph cantilever element structure were measured as a function of voltage using a Michelson interferometer

Dynamic Characteristics of Rainbow Ceramics

Abstract: The piezoelectric resonance behavior of end-clamped bimorph structures made from the rainbow monolithic ceramic have been evaluated. Thickness, width, width flexure, and length bending modes have been identified and measured. Using a very crude model in which the cermet component of the rainbow is assumed to have the same density × elasticity product as the bulk, surprisingly good agreement is obtained between observed and calculated frequency behavior. By appropriate processing it is possible to delaminate the bimorph, and work is now in progress to measure the properties of the two separate phases so that a proper composite resonator model may be developed.

Photostrictive effect in Plzt-Based ceramics and its applications

Abstract: Photostriction in ferroelectrics arises from a superimposed phenomenon of the photovoltaic and inverse piezoelectric effects. This paper reviews the recent developments in materials and their device applications: ion doping effect is described in (Pb, La)(Zr, Ti)O3 based ceramics firstly to improve the response speed, then the drive/control methods (polarized light method and dual beam method) are presented, finally photo-driven relays, micro walking machines and photoacoustic devices are introduced. The devices based on a bimorph structure were designed to start moving by the irradiation without any external electric circuit.

Continued development of a helicopter rotor model employing smart trailing-edge flaps for vibration suppression

Abstract: The continued development of a Froude-Scale helicopter rotor model featuring a trailing-edge flap driven by piezoceramic bimorph actuators for active vibration suppression is discussed. Block force and stroke of the current actuators are evaluated using two theories and compared with experimental results. Dynamic performance of the actuator as well as the actuator-flap assembly are examined. Earlier hover tests have shown severe degradation in flap deflections with increasing rotor speed, and flap deflections were too small to be effectively utilized for significant vibration control. To investigate the causes of the performance degradation, new blades are constructed and tested in-vacuo to isolate the effects of centrifugal loading on the actuator-flap system. A beam model of the piezo bimorph including propeller moment effects is formulated to better illustrate the physical mechanisms affecting the system in a rotating environment. The cause of the reduced deflections is traced to frictional forces created at the junction where the flap is supported during rotation of the blades. The use of a thrust bearing was found to alleviate this problem and subsequent tests on a hover stand showed a dramatic increase in flap detection at high excitation frequencies.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The use of piezoelectric bimorphs to measure forces in colloidal systems

Abstract: An analysis is made of the effect of errors introduced by bimorph drift and decay upon measurements of colloidal forces made with piezoelectric bimorphs. For direct measurements the errors will be small provided that the time constant of the bimorph, given by the product of its capacitance and amplifier input impedance, is much larger than the total time of measurement. With the force-feedback technique the errors will be negligible provided that, in addition, the integrator time constant is much smaller than the bimorph time constant, which condition is easily satisfied. It is important to use an amplifier with a very high input impedance to buffer bimorphs used for this type of measurement.

Dynamic bimorph matrix of end-loaded bimorphs

Abstract: Piezoelectric homogeneous benders consist of two strips of piezoelectric elements with opposing polarities joined along their length. The matrix elements relating the driving parameter (voltage across the piezoelectric elements) with the response parameters have been calculated for the bimorph with tip mass. These bimorphs can be used to move an object, such as a mirror in optics, a pyramid in atomic force microscopy, or for a chemical sensor at the tip. The effect of such an object at the tip is to lower resonance frequency, which is one of the immediately recognized results. The extra mass affects the capacitance at all frequencies and also changes all the resonance frequencies. The results of this work will enable us to design bimorphs whose deflection and resonance frequency can be controlled.

Actuator and its manufacture

Abstract: PROBLEM TO BE SOLVED: To obtain an actuator wherein constitution is simple and manufacturing is easy, by bending both members by using one ends of two members constituted of electromechanical transducing elements which are partly polarized in arbitrary directions, as a fixed fulcrum, and swinging the other ends of both of the members. SOLUTION: After two sheets of electromechanical transducing elements, e.g. piezoelectric boards 21, 22 are stuck sandwiching an intermediate electrode 23, and electrodes are formed on both of the whole surfaces, surface electrodes 24a, 24b, 25a, 25b which are divided into two parts are formed. A bimorph wherein the surface electrodes 24a, 24b, 25a, 25b are formed is polarized in parallel, and the electrodes 24a and 24b, and 25a and 25b are electrically connected. Thereby the actuator is constituted of a driving part of cantilever structure wherein an end part of the parallel polarized bimorph 201 is fixed, and a driving circuit wherein the respective terminals of an AC power supply 34 are connected with the surface electrodes 24a and 24b, and 25a and 25b of the parallel polarized bimorph 201. COPYRIGHT: (C)1997,JPO

Scanning apparatus and method

Abstract: An optical fibre (4) with a light-receiving end (18) is mechanically driven so that its end moves to scan an image, the optical fibre being driven to oscillate substantially at or near the natural resonant frequency of the fibre. The movement of the optical fibre is driven by at least one bimorph ceramic oscillator (20, 22). The light-receiving end of the fibre traces a scan path in the form of a time-varying Lissajous pattern.

Preparation and pyroelectrical investigation of bimorph polymer layers

Abstract: Two different procedures for the preparation of bimorph structures within nonlinear optical polymer layers are reported. One technique consists of thermally assisted poling above the glass-transition temperature followed by photo-induced poling below the glass-transition temperature. In this poling scheme, the second step is based on the photoisomerization of the dipole molecules. The other method comprises two consecutive thermally assisted poling steps with opposite field polarity in a double layer of two nonlinear optical polymers with different glass-transition temperatures. Pyroelectric thermal analysis is employed for analyzing the stability of the resulting bimorph structures, while pyroelectric depth profiling allows for a non-destructive qualitative analysis of their polarization distributions.

Dielectric and pyroelectric properties of a ceramic bimorph structure

Abstract: In this paper, pyroelectric and dielectric properties of a composite structure, with 2–2 connectivity, are studied. The originality consist in the fact that the two phases of the composite are pyroelectric ceramics with different Curie temperature. This structure, called pyroelectric bimorph, shows some interesting properties such as: apparent displacement of the Curie points of the two phases, enhanced pyroelectric coefficient (5.4 × 14−4 C/m2K for a series bimorph, which is greater than the pyroelectric coefficients of each of the two component phases) and others. The appearance of an electric field, during heating, is put into evidence. The behavior of the bimorph depends strongly on the rapport of the electrical time constants, τ = RC, of the two component phases.

Thermomechanical modeling of an actuated micromirror

Abstract: We have investigated numerically a micromirror actuated by the thermal bimorph effect. By performing coupled thermomechanical simulations with our MEMS modeling environment SOLIDIS, we have optimized the mirror structure with respect to maximum deflection for a given heating power. Numerical modeling gives insight into the response of the mirror, and reveals possible technological obstacles to device fabrication and operation.

Dynamics of a bistable snapping microactuator

Abstract: A study on the dynamics characteristics of a snap-action bistable microactuator that employs bimorph heating and residual-stress tension for switching behavior is presented. This study helps to characterize the device more completely and also provides valuable insights into the dynamic behavior of devices in micro-scale. The relation of bending moment and deflection during switching is numerically simulated by applying a simplified snap-through model. The model also takes air drag into consideration. The analysis shows that the switching time from one stable position to the other is less than 1 microsecond(s) , which is one thousand times shorter than the required cooling after each actuation. Hence, for the reported bistable microactuators that have overall lengths of about 200 micrometers and operate in air the maximum switching cycle time is expected to be in the kHz range that is based on thermal characteristics of the device.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Zig-Zag Piezoelectric Actuators: Geometrical Control of Displacement and Resonance

Abstract: The Zig-Zag actuator is a hybrid design combining bimorph and multilayer characteristics that is capable of producing and sensing usable motion in two dimensions. The mechanical impedance can be optimized by changing the angle between the legs and the actuator's working parameters controlled by changing the driving voltage and its frequency. Two interesting features of this actuator are its performance as a linear motor and its ability to drive a load in two directions.

A new control algorithm for bimorph mirrors

Abstract: A new control algorithm for bimorph mirrors is presented. The method is based on wave-front presentation by Zernike polynomials and application of a specific least square optimization technique for calculation of the control voltages. A complete control algorithm utilises the above-mentioned principles has been developed in application to bimorph deformable mirrors. The influence function matrix is calculated analytically and depends only on the electrode pattern and the set of surface-matching points and therefore, does not need to be recalculated for each surface function. The algorithm provides an accurate wave-front fitting by the deformable mirror surface in the least-square sense, and allows one to avoid the problems associated with the "one-to-one" control scheme, as it has been demonstrated by computer simulation of a bimorph mirror optical system with 11 control electrodes.

Design and development of a new class of piezoelectric actuators for force improvement

Abstract: Piezoelectric actuators are useful for smart structure applications because they are light weight, compact and fast compared to other types of actuators. The two most common configurations, bimorph and stack, have significant limitations on the available force and deflection, respectively, which can be produced. This paper describes a new class of piezoelectric bimorph actuators that supply larger force than the traditional straight cantilever beam bimorph design. These actuators, called C-blocks because of their half circle shape, can produce approximately five times the force of the traditional design with only a slight decrease in the deflection. In addition, they can be combined in series or in parallel like building blocks to form larger actuators that provide improved deflection and/or force capabilities. This paper presents a mathematical model that provides an approach to designing and predicting the force performance of a C-block architecture. This paper also summarizes a set of manufacturing techniques developed to fabricate C-block architectures from polymeric piezoelectric material Polyvinylidene Fluoride (PVdF). These techniques were used to manufacture prototypes used in a Force-Voltage experiment that was performed to measure force performance. The results from these experiments confirm the mathematical model is accurate and the force performance of a C-block architecture is substantially increased in comparison to the force generated from a traditional straight beam bimorph.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Optical Servo System Using Bimorph PLZT.

Abstract: This paper deals with an optical servo system using a bimorph PLZT actuator which has relatively large displacement. This optical actuator works by controlling the intensity of irradiated U. V. beam using the feedback controller. An optical actuator servo system is proposed as a mathematical model of the optical actuator, and the transfer function of the optical servo control system is identified. Optical servo control experiments are conducted. To improve the response of the bimorph PLZT actuator, U. V. beams are irradiated on both sides of it. We also show the experimental results of the double-sided U. V. beam irradiation.

Dynamic matrix of end-loaded piezoelectric bimorphs

Abstract: A bimorph cantilever consisting of two oppositely polarized piezoelectric elements, fixed at one end, and loaded by a discrete mass at the other, is considered. It is regarded as driven by any combination of end force, end moment, surface pressure, and voltage. Its responses consist of end deflection, end slope, volume displacement, and electric charge. The dynamic admittance matrix of the structure is developed assuming simple Euler-Bernoulli beam theory applies.

Bimorph piezoelectric element and manufacture thereof

Abstract: PURPOSE: To provide a bimorph piezoelectric element having a large amount of displacement and a method of manufacturing the element. CONSTITUTION: A Cr-Au deposition is performed on the main surfaces of piezoelectric ceramic plates 1 and 2, which are polished into a prescribed thickness, using a piezoelectric ceramic material of a Curie point of 140°C or lower to form electrodes 3 and 5, two sheets of the plates 1 and 2 are bonded together at a high temperature via a shim material 4 consisting of a carbon fiber reinforced Invar, are cured to laminate together and after that, an electric field is applied to perform a polarization treatment. COPYRIGHT: (C)1996,JPO

Improvement of micro mobile machine with piezoelectric driving force actuator

Abstract: As a micromachine driving force generation mechanism, a pin-type actuator, made up of a piezoelectric bimorph plate with a contact pin to generate the 2-dimensional driving force, has been studied with the aim of miniaturization. Miniaturized pin-type actuators with bimorph plate size of 6.5 mm/spl times/6.5 mm and 5 mm/spl times/5 mm have been prepared, and their fundamental performances were examined to estimate the micro characteristics. Also, the micro mobile machine in tube has been improved so as to set the driving circuit into the machine body and its performances have been also evaluated. Vibrational analysis of a pin-type actuator with a size of 26 mm/spl times/26 mm has been performed by finite element analysis with the piezoelectric coupling effect. As a result, the superposition of natural vibrational modes with the phase difference appears to generate the directional driving force at the contact pin tip.