Showing papers on "Bimorph published in 1997"

Composite piezoelectric transducer with truncated conical endcaps "cymbal"

Abstract: This paper presents original results obtained in the development of the moonie-type transducers for actuator applications. The moonie-type actuators fill the gap between multilayer and bimorph actuators, but its position-dependent displacement and low generative force are unacceptable for certain applications. The moonie transducers were modified systematically by using finite element analysis combined with experimental techniques. A new transducer design, named "cymbal transducer", was developed with larger displacement, larger generative forces, and more cost-effective manufacturing. The cymbal transducers consist of a cylindrical ceramic element sandwiched between two truncated conical metal endcaps and can be used as both sensors and actuators. The cymbal actuator exhibits almost 40 times higher displacement than the same size of ceramic element. Effective piezoelectric charge coefficient, Eff. d/sub 33/, of cymbal is roughly 40 times higher than PZT itself.

A novel micropump design with thick-film piezoelectric actuation

Abstract: A new design for a silicon-based micropump is described. Passive cantilever valves are produced by boron etch stop and fusion bonding. Tests of these valves show good performance, as no flow could be detected in the reverse direction. Initial experiments on a thick-film screen printed piezoelectric membrane actuator were undertaken. A study of suitable inks for electrodes on different insulation layers on silicon yielded silicon dioxide and cermet gold ink as the most satisfactory combination. Deflection measurements of a mm PZT (lead zirconate titanate) - bimorph membrane gave movement at an applied voltage of 100 V. A quasi-static simulation package of the flow through a micropump is also presented. The valve action is simulated using ANSYS coupled with FLOW3D. The piezoelectric membrane deflection is simulated with ANSYS. A differential equation for the combined actuation of membrane and valves is solved numerically with Maple. Pump rates of up to and a maximum backpressure of up to 70 kPa for a driving voltage of 40 V have been modelled using bulk values for PZT-5H. A pump rate of up to and a maximum backpressure of up to 35 kPa at 100 V driving voltage are predicted using thick-film parameters extracted from the measurements.

Two-dimensional micromechanical bimorph arrays for detection of thermal radiation

Abstract: We demonstrate that two-dimensional arrays of micromechanical bimorphs can be used as thermal sensors to image infrared (IR) radiation. A density of 100 pixels per mm2 is achieved by coiling a bimorph beam into the shape of a flat spiral. Temperature variations of a given spiral are converted to modulations of visible light by illuminating the spiral array with a visible source. The optical properties of the spiral resemble a Fresnel zone plate when light reflected off neighboring rings of the spiral is focused. When a spiral is heated through the absorption of IR radiation, thermally induced bending of the bimorph degrades the focusing efficiency by distorting the spiral. This reduces the optical intensity at the focal point. Arrays of spirals can be monitored with a commercial CCD camera. At 40 Hz, the temperature resolution and noise equivalent power of a 75 μm diam spiral are 50 μK/√Hz and 20 nW/√Hz, respectively, and the thermal response time is 270 μs.

Bimorph piezoelectric microactuator head and flexure assembly

Abstract: A head flexure assembly for positioning a transducing head over a selected track of a rotatable disc in a disc drive system having an actulator arm and head suspension includes a bimorph piezoelectric microactuator having first and second ends. The first end of the microactuator is attached to the actuator arm, and a flexure is attached to the second end of the microactuator. A slider carrying the transducing head is attached to the flexure.

Theory of piezoelectric axisymmetric bimorph

Abstract: A theory of a piezoelectric axisymmetric bimorph is presented in this paper. Bimorphs are often used as electroacoustic transducers, but their use is much wider. A piezoelectic bimorph consists of two or more layers which are placed asymmetrically to the middle surface of the structure. When voltage is supplied to the bimorph, a bending moment is produced which causes transversal deflections of the structure. Average elastic parameters are calculated. Equations for the calculation of bending moments and stretching forces produced by voltage are derived. When the bimorph is a shell of revolution with any shape of meridian, the derived equations can be solved by numerical methods. The finite-element method (FEM) is applied to solve this problem. The bimorph can also be used as a sensor. A theory of such a sensor is also presented. The results obtained by means of the described theory and numerical methods have been verified experimentally or by comparing them with results obtained analytically for a simple structure. It has been proved theoretically that the electric signal produced by a circular transducer clamped on the outer rim of a piezoelectric disc is equal to zero.

Organic thermal and electrostatic ciliary microactuator array for object manipulation

Abstract: An organic thin-film ciliary microactuator array using independent thermal and electrostatic actuation is described. A polyimide thermal bimorph structure provides for large angle deflection with high load capacity. Electrostatic electrodes provide low-power hold-down, capacitive sensing, and feedback control capabilities. Integrating four orthogonally oriented actuators into a unit cell and replicating this cell into an array allows for precise movement of small objects in arbitrary directions. The ciliary microactuator array has immediate applications for positioning, alignment, inspection, and assembly of small parts, such as IC dice, with micron-scale resolution.

A micro variable inductor chip using MEMS relays

Abstract: An adjustable inductor which is digitally controlled by microrelays has been made using combined surface and bulk micromachining technology. The microrelays were fabricated using a TaSi/sub 2//SiO/sub 2/ bimorph cantilever beam, a gold-to-gold electrical contact, aluminum as sacrificial layer, and a combined electrostatic and thermal actuation mechanism. The silicon substrate underneath the inductor region was etched out to reduce the substrate eddy current loss. Sixteen different inductance values ranging from 2.5 nH to 324.8 nH were obtained using four microrelays. The minimum self-resonant frequency is 1.9 GHz. The lowest measured thermal power and electrostatic voltage for the combined actuation of microrelays are 8.0 mW and 20 V, respectively. The measured contact resistance is typically 0.6 to 0.8 ohms.

Frustrated total internal reflection device

Abstract: A device for processing an optical signal includes a refractor with a reflecting surface for reflecting the optical signal by frustrated total internal reflection. In one embodiment, the device includes a bimorph transducer coupled on one end to the refractor and on the opposing end to a switchplate. In another embodiment, two ends of the bimorph transducer are coupled to the refractor and the switchplate is coupled between the two ends.

Resonance and antiresonance of symmetric and asymmetric cantilevered piezoelectric flexors

Abstract: The resonances of dynamically excited symmetric piezoelectric bimorphs have been determined from the equations of state Under the effect of sinusoidal stimuli: a moment exerted at the tip M, a force exerted perpendicular to the plane of the bimorph also applied at the tip F, a uniformly applied pressure p, and an electrode voltage V, they respond with a sinusoidal tip rotation /spl alpha/, tip deflection /spl delta/, volume displacement /spl nu/, and electrode charge Q All of the former are related to all of the latter through a dynamic admittance matrix B The antiresonance frequency of the capacitance C have been found while also antiresonance in off-diagonal elements have been determined The latter indicate that at these frequencies the bimorph does not work as an actuator or sensor in the particular domain of the off-diagonal The mode shape at these antiresonance frequencies has been determined The antiresonance of b/sub 14/ determines that for this frequency the tip has deflection but no rotation, while the antiresonance of b/sub 24/ indicates that the tip has rotation but no deflection No antiresonance in the volume displacement is found, indicating that the bimorph is a pressure converter (microphone) at all frequencies Micromachined piezoelectric heterogeneous bimorphs have been fabricated using the techniques of IC fabrication Their deflections have been measured as a function of frequency and applied voltage, while these have been compared with the theoretical predictions An anomalously large quadratic deflection has been found, superimposed on the linear piezoelectric behavior The agreement between the linear part of the experimental deflection and the theory was quite good

Comparative analysis of piezoelectric bending-mode actuators

Abstract: During the last several years novel piezoelectric bending actuators have been developed: RAINBOW, CERAMBOW, CRESCENT, d33 bimorph and THUNDER. A comparative experimental investigation of electromechanical characteristics of these devices along with conventional d31 bimorph and unimorph actuators was conducted in this work. All transducers were fabricated from soft piezoelectric ceramics. The experimental results show the d33 bimorph and unimorph elements have superior quasistatic characteristics as compared to other type of bending-mode actuators. All these piezoelectric devices demonstrate a significant dependence of electromechanical performance on the magnitude of the driving electric field. It was found that the decrease in the mechanical quality factor and resonant frequency of bending vibrations in d31 unimorph, RAINBOW, CRESCENT (CERAMBOW) and THUNDER with increasing electric field is much smaller than that in bimorph and d33 unimorph actuators. The dependence of the behavior of these devices on the operating conditions governs the selection of a particular device for a specific application.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

New applications of photostrictive ferroics

Abstract: Photostriction in ferroelectrics arises from a superposition of photovoltaic and inverse piezoelectric effects. (Pb,La)(Zr,Ti)O3 ceramics doped with WO3 exhibit large photostriction under irradiation of near-ultraviolet light, and are applicable to remote control actuators and photoacoustic devices. Using a bimorph configuration, a photo-driven relay and a micro walking device have been developed, which are designed to start moving as a result from the irradiation, having neither electric lead wires nor electric circuits. The mechanical resonance of the bimorph was also induced by an intermittent illumination of purple-color light; this verified the feasibility of applying photostriction for ”photophone” applications.

Development of micro-electro-mechanical optical scanner

Abstract: Rockwell is working on the development of a micro-electromechanical optical scanner based on bimorph microactuators. This scanner is lightweight, is small, and has superior scanning performance. The scanner is a low-power (<1 W) device that has large scan angles (?20 deg) and scan rates in the range of 100 to 2000 Hz. It works for all wavelengths and offers the potential for monolithic integration with both electronics and optics for on-chip signal processing and control. The optical scanner consists of two main components—actuator and mirror— which are fabricated on a silicon cantilever beam. The actuator is comprised of a bimorph layer covered with two metal layers, which function as top and bottom electrodes. The mirror can be as large as 12 mm2 in area, is placed at the end of the cantilever beam, and is designed for maximum optical flatness. The optical efficiency of the device is very high and can exceed 90% on proper metallization of the mirror area. The scan angle is a function of beam thickness, power efficiency of the bimorph, and many other design criteria. Through many improvements in these design parameters, a scan angle greater than 20 deg is expected to be achieved with high yield.

A comparative analysis of piezoelectric bending-mode actuators

Abstract: During the last several years novel piezoelectric bending actuators have been developed: RAINBOW, CERAMBOW, CRESCENT, d 3 3 bimorph and THUNDER A comparative experimental investigation of electromechanical characteristicsof these devices along with conventional d 3 1 bimorph and unimorph actuators was conducted in this work. All transducers were fabricated from soft piezoelectric ceramics. The experimental results show that d 3 3 bimorph and unimorph elements have superior quasistatic characteristics as compared to other type of bending-mode actuators. All these piezoelectric devices demonstrate a significant dependence of electromechanical performance on the magnitude of the driving electric field. It was found that the decrease in the mechanical quality factor and resonant frequency of bending vibrations in d 3 1 unimorph, RAINBOW, CRESCENT (CERAMBOW) and THUNDER with increasing electric field is much smaller than that in bimorph and d 3 3 unimorph actuators. The dependence of the behavior of these devices on the operating conditions governs the selection of a particular device for a specific application.

A finite-element static analysis of smart turbine blades

Abstract: Piezoelectric materials are becoming increasingly popular in the emerging field of adaptive structures. In particular, active control of wings and helicopter rotors using these materials is being pursued currently. The present work is an effort at modeling piezoelectric actuated blades for turbomachinery applications. A laminated general quadrilateral shell finite element with eight nodes and curved edges is developed for this purpose. the mathematical formulation of the element is described. Experiments have been conducted on a commercially available piezoceramic bimorph. Our finite-element and experimental results are shown to match very well. The laminated element developed is then used to perform a static analysis of typical turbomachinery blades. Effects of the angle of pre-twisting and aspect ratio have been studied. PVDF and PZT piezoelectric materials have been compared.

Multi-layered piezoelectric bimorph actuator

Abstract: We have developed a multi-layered bimorph actuator whose power consumption is low and whose displacement is large. Each actuator layer comprises a piezoelectric element and elastic plate. Because volume of the piezoelectric element is constant, the actuator expands in the direction of applied voltage, but contracts in the perpendicular direction. This bends the elastic plate, amplifying displacement. Layer number determines actuator force. We also developed in-pipe locomotive mechanism utilizing the developed actuator and conventional stack type piezoelectric actuator. The power consumption and moving speed of two-actuator mechanism were investigated. The mechanism of the multi-layered actuator moves 2.5 times faster compared with that of the conventional one, and consumes only 1/80 of electric power of the conventional one.

Analysis and Testing of a Froude Scaled Helicopter Rotor with Piezoelectric Bender Actuated Trailing Edge Flaps

Abstract: This paper presents an analytical model and validation tests of a Froude scaled rotor featuring piezoelectric bender (bimorph) actuated trailing-edge flaps for active vibration suppression. The analytical model for the coupled bimorph actuator trailing-edge flap dynamic response in the rotating environment takes into account the aerodynamic, centrifugal, inertial and frictional loads acting on the actuator-flap system. The linkage arm length associated with the mechanical amplification mechanism is selected to maximize flap performance in the rotating environment. The bimorph clamping is improved to prevent actuator slippage under high centrifugal loads. The analytical model is validated by carrying out a series of bench tests, vacuum chamber tests and hover tests. In hover, flap deflections of ± 6 degrees at 4/rev flap excitation are achieved at 900 RPM, thus demonstrating the potential ofthe piezoceramic bender as a lightweight and compact actuation system for individual blade control purposes. This paper also includes a feasibility study for piezo-bimorph actuation of a trailing-edge flap for a Mach scaled rotor model.

A new MEMS wafer probe card

Abstract: This work presents a new type of wafer probe card consisting of an array of microcantilevers actuated by bimorph heating to make contact with the contact pads on a device chip during wafer-stage testing. The microcantilevers are meant to be operated either in air or in vacuum. Bending action is created through Joule heating of a bimorph film element on the cantilever. The deflection efficiency d/spl delta//dP ranges from 5.8 to 9.6 /spl mu/m/mW (depending on lever parameters), the force efficiency dF/dP ranges from 1.4 to 5.5 /spl mu/N/mW; maximum controllable (reversible) deflection is in the range of 150 /spl mu/m, and contact resistance to a gold pad is approximately 1 /spl Omega/.

Displacement control actuator

Abstract: Rectangular piezoelectric substrates each of which has main surfaces opposed to each other, measures 50 μm thick by 1 mm wide by 8 mm long, and is made of lithium niobate (LiNbO3), are directly bonded on the main surfaces so that their axes of polarization are set in directions reverse to each other, thereby composing a piezoelectric element. Electrodes which are 0.2 μm thick and made of chromium-nickel are formed on the two main surfaces of the piezoelectric element opposed to each other, thereby resulting in a precision displacement control actuator of a bimorph type mechanical-electrical converter element. This configuration makes it possible to provide a compact precision displacement control actuator which has a large displacement and extremely small variations of characteristics such as displacement and resonance frequency.

Testing and validation of a Froude-scaled helicopter rotor model with piezo-bimorph-actuated trailing edge flaps

Abstract: This paper presents the testing of a Froude scaled rotor featuring piezoceramic bimorph actuated trailing-edge flaps for active vibration suppression. An analytical model for the coupled bimorph actuator trailing-edge flap dynamic response in the rotating environment was developed. The analysis takes into account the aerodynamic, centrifugal, inertial and frictional loads acting on the actuator-flap system. The linkage arm length associated with the mechanical amplification mechanism was selected in order to maximize flap performance in the rotating environment. The bimorph clamping was improved to prevent actuator slippage under high centrifugal loads. The analytical model was validated by carrying out a series of bench tests, vacuum chamber tests and hover tests. In hover, flap deflections of plus or minus 6 degrees at 4/rev flap excitation were achieved at 900 rpm, thus demonstrating the potential of the piezoceramic bender as a lightweight and compact actuation system for individual blade control purposes. This paper also includes a feasibility study for piezo-bimorph actuation of a trailing-edge flap for a Mach scaled rotor model.

Optical device for compensating the dispersion of optical signals

Abstract: An optical device comprises an optical fibre device having wavelength-dependent optical characteristics mounted on a bimorph element operable to bend in response to an electrical control signal, so that the wavelength-dependent optical characteristics of the optical fibre device vary in response to bending of the bimorph element.

Piezoelectric ceramic disks with thickness-graded material properties

Abstract: A system of two-dimensional first-order equations for electroded piezoelectric crystal plates with general symmetry and thickness-graded material properties was recently deduced from the three-dimensional equations of linear piezoelectricity. These equations are much simplified for the two limiting cases of thickness-graded piezoelectric properties, i.e., the homogeneous plate and bimorph of piezoelectric ceramics. Closed form solutions are obtained from these reduced equations for the flexural and thickness-shear vibrations and static response of bimorph disks as well as for the extensional and thickness-stretch vibrations of homogeneous disks. Frequency spectra and modes are computed and examined. Resonance frequencies for both homogeneous and bimorph disks of PZT-857 are computed and measured. The comparison of the results shows that the agreement is close.

Position control of PLZT bimorph-type optical actuator by on-off control

Abstract: An optical actuator consisting of PLZT elements is a new type of actuator that makes active use of energy and information of light, and is inherently robust to electromagnetic noise. PLZT is an element that produces mechanical strain by the photostrictive effect when irradiated by ultraviolet light. Since displacement of the element is very small, we adopt a bimorph structure for the optical actuator to increase the displacement. In this paper, we propose an effective position control method for the bimorph-type optical actuator; its validity is confirmed by experiments. A simple on-off control is insufficient to control the optical actuator because the mechanical shutters controlling light irradiation have a large time lag. A new control method, taking into account the dynamic response of the optical actuator and the shutters is introduced into the system, and improves the precision and response speed of the optical actuator.

Piezoelectric-body power generating apparatus and power supply provided with it as well as electric equipment

Abstract: PROBLEM TO BE SOLVED: To provide a power generating apparatus which can be used actually, which is small and which is provided with a charging capability and to provide a small portable electronic equipment using it by a method wherein a conversion efficiency to convert strain energy into electric energy is enhanced in the power generate apparatus which contains a piezoelectric element which generates electricity when a strain is applied. SOLUTION: A lithium niobate vibrating piece 21 is polarized into a polarization direction 310 and a polarization direction 311 without the intermediary of an adhesive layer, and the bimorph vibrating piece 21 without an inverting polarization layer or without an adhesive layer due to a direct bonding operation is formed. In the vibrating piece 21, the internal loss of a material is small, an adhesive loss does not exist, a vibration is hard to attenuate, and electric energy can be taken out by making use of the vibration. In addition, when an optimum cut angle is selected, strain energy can be converted into electric energy with good efficiency by one deformation, and a power generation apparatus whose mechanical-to-electric conversion efficiency is high can be realized.

Device for receiving or rejecting coins or circular tokens

Abstract: This invention relates to a device for receiving or rejecting coins or circular tokens, for example for coin- or token-operated telephone apparatus. It comprises, for the chute down which the coins drop, a pivoting flap of which the state, retracted or not due to the weight of an incidental coin, is determined by a piezoelectric element, such as a bimorph piezoelectric plate, which serves, or not, as anti-pivot support for this flap.

Determining spring stiffness by the resonance frequency of cantilevered piezoelectric bimorphs

Abstract: The dynamic behavior of a bimorph clamped at one end and constrained by a linear spring at the other end was studied. The fundamental resonance frequency of the bimorph increased by an amount related to the spring stiffness when compared to the case where the end was free. Therefore, a cantilever bimorph provides a technique to assess the stiffness of a material by a simple measurement of the resonant frequency. Since the bimorph behavior is determined in part by its geometry, the device can be designed for mechanical measurement of microscopic systems such as living cells.

Temperature dependence of the pyroelectric voltage in a 2–2 connectivity pyroelectric bimorph

Abstract: Parallel and series pyroelectric bimorph structures, with 2–2 connectivity, are theoretically analysed to obtain the electric fields inside the two component phases. The proposed model takes into consideration the possibility of an electrical interaction between the two phases. It is demonstrated that the value of the internal electric field, due to the pyroelectric charge generated during heating of the bimorph structure, is considerably different than the case where each of the two phases is heated separately. It is shown that the value and the orientation of the electric fields inside the two phases of the bimorph depend on the value of the pyroelectric coefficients and dielectric constants of the two phases. The most interesting result is obtained in the case of the series bimorph, where the orientation of the electric field inside the phase with a lower pyroelectric coefficent is opposite to the orientation of spontaneous polarisation of this phase.

Driving Principles for Magnetic Thin-Film Cantilevers

Abstract: This paper describes a theoretical analysis of the mechanical properties of magnetic thin-film cantilevers for micro-electromechanical systems. Magnetostriction and magnetic torque were used as driving principles in this study. The magnetostriction-driven cantilever had a bimorph structure, composed of TbFe and SmFe thin films, and the torque-driven one had a metal powder (MP) thin film or a rare-earth magnet thin film. The static deflection and force produced by both cantilevers were calculated by the theory of elasticity. As a result, it was found that the conditions suitable for each driving principle depended on the ratio of thickness to length and the intensity of the applied magnetic field.

Large-area fiber optic display using piezoelectric shutters

Abstract: A piezoelectric shutter (24) is arranged in a comb pattern (26) and presents a core. The comb is provided with at least one tooth constituting the shutter, the bore being arranged with elevation allowing the displacement of the shutter by the piezoelectric effect. The device is remarkable in that it comprises at least one bimorph (14) arranged on the support, capable of being raised with respect to the support by the piezoelectric effect.

Objective lens driving device

Abstract: PROBLEM TO BE SOLVED: To provide an objective lens driving device capable of exhibiting high-speed access performance by improving the vibration resistance and impact resistance in biaxial directions; a focusing direction and a tracking direction. SOLUTION: The objective lens driving device 1 used for an optical pickup device has an objective lens 9 for condensing the light beam emitted from a light source to a signal recording surface of a magneto-optical disk, etc. The device has a pair of bimorph type piezoelectric elements 7, 7 which freely movably support this objective lens 9 in the focus direction via a lens holder 8 and a pair of laminated piezoelectric elements 10, 10 which support a pair of these bimorph type piezoelectric elements 7, 7 via the hinge part 3b, etc., of a base 3 in such a manner that the objective lens 9 is movable in the tracking direction. The objective lens 9 is driven in the focus direction in the vertical direction by the distortions of the respective bimorph type piezoelectric elements 7, by which the focusing adjustment is executed. The objective lens is driven in the tracking direction in the lateral direction by the distortions of the respective laminated piezoelectric elements 10, by which the tracking adjustment is executed.