Showing papers on "Bimorph published in 1998"

Micro-electromechanical (MEM) optical resonator and method

Abstract: An integrated micro-electromechanical (MEM) optical resonator comprises a cantilever beam which is fixed to a substrate at one end and extends freely over the substrate at the other end, and a bimorph actuator stacked atop the beam at its fixed end. A reflective surface partially covers the top of the beam at its free end. The bimorph actuator comprises material layers having different thermal expansion coefficients. A DC-biased AC voltage connected across the actuator causes it to heat and cool as the current passing through it increases and decreases, creating a thermal bimorph effect which causes the cantilever beam and the reflective surface to oscillate in accordance with the varying current, preferably at the beam and actuator structure's fundamental resonant frequency. Combining the resonator with a light source and actuator excitation circuitry creates an optical scanner engine which delivers a scan angle in excess of 20 degrees and a scan rate of up to 2000 Hz, using a driving voltage of only 2 Vp-p.

Performance analysis of piezoelectric cantilever bending actuators

Abstract: Bimorph and unimorph are two typical bending mode actuators, either consisting two piezoelectric layers or one piezoelectric layer and one elastic layer. In the case of bimorph actuator, when an electric field is applied to the piezoelectric layers, one layer expands while the other contract along length direction, producing a pure bending deformation. In unimorph actuator, when piezoelectric layer is driven to expand or contract, the elastic layer will resist this dimension change, both bending and stretching deformation will be resulted. These actuators can generates very large tip displacement, in the range of tens micron to several millimeters, depending on the geometrical dimensions of actuators. In this paper, to describe the performance of cantilever bimorph/unimorph actuators in quasi-static driving condition, analytical expressions are derived to relate bending resonance frequency, tip deflection, blocking force and equivalent moment with actuator geometrical dimensions. Young's modulus,...

A bistable microrelay based on two-segment multimorph cantilever actuators

Abstract: A surface micromachined bistable microrelay based on the latching of a novel two-segment multimorph cantilever actuator is presented. The two-segment multimorph actuator is composed of two bimorph segment actuators that are connected with each other, one is normally open (NO) and the other is normally closed (NC). The two bimorph segments can be actuated independently in such a way that the device has two stable mechanical latching states, namely, "on" and "off", which can be electrically read out with large off/on resistance ratios. This bistable relay is operated by two separate thermal power pulses at 12 mW and 10 mW respectively. The latching "on" and unlatching "off" operation times are less than 0.5 msec and 0.1 msec respectively. The "on" resistance is in the range of 2.1 /spl sim/35.6 ohms. The "off" resistance is greater than 10/sup 12/ ohms. The breakdown voltage between the open electrodes is above 400 V. Keeping the NO bimorph segment of the bistable relay activated, a normally closed microrelay is also demonstrated.

Low-order adaptive deformable mirror.

Abstract: We report the main parameters of a nine-electrode bimorph piezoelectric adaptive mirror designed to correct low-order aberrations. We describe measurements of the control coefficients for defocus, astigmatism, pure coma, and spherical aberration of this mirror and the temperature stability of its profile. The performance of a simple adaptive optical system for imaging through laboratory-generated turbulence is investigated. This low-order device is suitable for small (<1-m-diameter) telescopes and for nonastronomical applications of adaptive optics.

Multi-segmented piezoelectric mirrors as active/adaptive optics components

Abstract: The angular acceptance of piezoelectric (Pzt) bimorph mirrors is limited by the maximum length of commercially available Pzt ceramic plates. To overcome this limit and manufacture longer devices, several (2n + 1) 150 mm-long bimorph Pzt stacks were assembled side-to-side. Two prototype mirrors, 450 (n = 1) and 750 (n = 2) mm long, were designed, assembled, polished and optically characterized. They are fully UHV compatible and are now installed in the monochromatic section of the ESRF beamlines ID26 and ID32. Both mirrors cover the full range of required bending radii (1 km concave–3.5 km convex). Junctions between segments do not spoil the optical surface quality. The surface slope error r.m.s. can be kept well below 1 arcsec over the full bending range. Adaptive compensation for low-frequency figure errors was shown to be easy and reliable. After compensation, residual shape errors are of the order of 40 nm r.m.s. over 700 mm.

Microelectromechanical positioning apparatus

Abstract: A microelectromechanical (MEMS) positioning apparatus is provided that can precisely microposition an object in each of the X, Y and Z directions. The MEMS positioning apparatus includes a reference surface, a support disposed in a fixed position to the reference surface, and a stage defining a XY plane that is suspended adjacent to the support and over at least a portion of the reference surface. The MEMS positioning apparatus also includes at least one and, more typically, several actuators for precisely positioning the stage and, in turn, objects carried by the stage. For example, the MEMS positioning apparatus can include first and second MEMS actuators for moving the stage in the XY plane upon actuation. In addition, the MEMS positioning apparatus can include a Z actuator, such as a thermal bimorph structure, for moving the stage in the Z direction.

A bimorph based dilatometer for field induced strain measurement in soft and thin free standing polymer films

Abstract: A bimorph based dilatometer has been developed which enables one to characterize the electric field induced strain response in the out-of-plane direction in thin and soft free standing polymer film samples conveniently over a relatively wide frequency range (1 Hz to 1 kHz). The test results demonstrate that the newly developed dilatometer is capable of detecting displacement down to sub-angstrom range. The agreement between the test results from the bimorph dilatometer, the results from a laser dilatometer, and the model analysis indicates that the device can indeed be used reliably for these measurement with high sensitivity.

Piezoelectric assembly for micropositioning a disc drive head

Abstract: An assembly and method for micropositioning a disc drive head is described. An implementation of the assembly includes a gimbal, a piezoelectric element bonded to the gimbal and electrically connected to a voltage source, and a slider connected to the piezoelectric element. The assembly may also include at least a second piezoelectric element bonded to the gimbal and connected to the slider. The piezoelectric elements may be made of PZT material, and each may be in a monomorph or bimorph configuration.

Damper and valve

Abstract: A valve regulates fluid displacement in a damper assembly. The valve is placed between a portion of fluid at one pressure and regulates the passage of fluid through an aperture or passage (20) to a portion of fluid at a lower pressure by a blocking member (26) which moves to obstruct the aperture in accordance with a desired level of damping. The blocking member is, or is driven by, an electroactive device, such as a bimorph actuator formed of ferroelectric material. In one embodiment, the blocking member is a bimorph which covers the aperture, and is flexibly displaced by passage of pressurized fluid through the aperture. A controller provides an electrical actuation signal to move the bimorph toward or away from the aperture, augmenting or decreasing its closing bias to affect both the threshold flow initiation pressure and the rate of flow once the passage opens. Preferably the blocking member is a flexible piezoelectric assembly, which moves across a gap to provide a varying obstruction in the near field of fluid flow as the fluid moves through the passage. Preferably, a position sensor connected to the controller senses piston position, and the controller operates to energize the bender and to obstruct the opening or to further restrict flow if the piston position or its velocity is determined to lie above a threshold. This extends the useful range of the damper and may allow optimal stroke of the damper during all conditions of use, enhancing comfort while preventing bottoming out.

Forward-scanning ultrasound catheter probe

Abstract: A forward-scanning ultrasound catheter probe. An ultrasound catheter probe includes a forward-scanning transducer positioned at the tip of the probe. As such, the forward-scanning transducer may provide images of structures that may lie ahead of the tip of the probe. Furthermore, the forward-scanning transducer is repositioned by a drive mechanism coupled to the front-scanning transducer to provide a sector scan. In one embodiment, a bimorph piezoelectric drive is utilized to sweep the forward-scanning transducer across an arc to provide an imaging area associated with a sector scan.

Governing equations for a piezoelectric plate with graded properties across the thickness

Abstract: Two-dimensional first-order governing equations for electroded piezoelectric crystal plates with general symmetry and thickness-graded material properties are deduced from the three-dimensional equations of linear piezoelectricity by Mindlin's general procedure of series expansion. Mechanical displacements and thickness-graded material properties, i.e., the elastic stiffnesses, piezoelectric coefficients, dielectric permittivities, and mass density, are expanded in powers of the thickness coordinate, while electric potential is expanded in a special series in order to accommodate the specified electric potentials at electroded faces of the plate. The effects of graded material properties on the piezoelectrically induced stresses or deformations by the applied surface potentials are clearly exhibited in these newly derived equations which reduce to Mindlin's first-order equations of elastic anisotropic plates when the material properties are homogeneous. Closed form solutions are obtained from the three-dimensional equations of piezoelectricity and from the present two-dimensional equations for both homogeneous plates and bimorphs of piezoelectric ceramics. Dispersion curves for homogeneous plates and bimorphs and resonance frequencies for bimorph strips with finite width are computed from the solutions of three-dimensional and two-dimensional equations. Comparison of the results shows that predictions from the two-dimensional equations are very close to those from the three-dimensional equations.

Parallel plate structure provided with pzt thin-film bimorph and method of fabrication thereof

Abstract: A parallel plate structure (1) is provided with a pair of bimorph piezoelectric elements (2) and prismatic insulation spacers (3) inserted between the piezoelectric elements (2) at the upper and lower ends thereof for cementing the piezoelectric elements (2) together via the spacers (3). Each piezoelectric element (2) comprises a planar base material (4) of titanium, PZT thin films (5) formed on both sides of the base material (4) by the hydrothermal method, and electrode films (6) formed on the PZT thin films (5). The base material (4) is 20 νm thick and the PZT thin films (5) are several νm thick, while the aluminum electrode films (6) are several νm thick.

Application of Gas Jet Deposition Method to Piezoelectric Thick Film Miniature Actuator.

Abstract: Currently the development of piezoelectiric miniature actuators is a subject of interest in the industrial field of mobile electronic devices. Although the deposition of PZT(Pb(Zr.52, Ti.48)O3) in the thickness range of 10 to 100 µm is a key technology for the realization of miniature actuators, thick films of PZT have rarely been prepared by other deposition methods for glued PZT structures. It is also difficult to obtain a thickness of less than 50 µm. This is the reason why we have designed and fabricated a two-dimensional miniature scanner actuated with a relatively thick piezoelectric layer by a recently introduced gas deposition method of ultra fine particles with a subsonic gas jet stream. A piezoelectric PZT layer, of thickness 30 microns is deposited onto a stainless steel substrate and patterned by the simple lift off method, to fabricate a bimorph type actuator beam. Mirror scanning is performed by four independent actuator beams. The device can be scanned along two axes by two independent resonant frequencies. Deflection of the fabricated scanning mirror is measured by laser interferometer and compared with the simulation results obtained by FEM (finite element method). Scanning of the laser light is also demonstrated by the fabricated device.

Design and fabrication of piezoceramic bimorph vibration sensors

Abstract: A bimorph-type piezoceramic vibration sensor is developed that can make up for the shortcomings of current mass loaded type sensors, such as high price, low sensitivity, and complex structures. For the design, in conjunction with piezoelectric constitutive equations, we derive full analytic response equations of the bimorph sensor to external forces. As the external forces, two representative cases are considered, step and sinusoidal excitation. Based on the results, actual sensors are fabricated and tested for verification of the theoretical results. Thermal stability of the bimorph structure is also checked through experiments. Further, a comparison of performance of the developed sensor is made with that of a commercial reference sensor so that quantitative evaluation of its sensitivity can be made. The sensor developed in this work shows excellent sensitivity and thermal stability in addition to the merits of simple structure and ease of fabrication. The design procedure with the sensor voltage response equations derived in this paper can be applied to develop piezoelectric bimorph sensors to meet any practical specifications.

Scanning device using fiber optic bimorph

Abstract: An optical scanner employs a cantilever-mounted optical fiber within a micro electro-mechanical systems (MEMS) motor. In an embodiment, the fiber is sandwiched between two piezoelectric elements to form a unitary bimorph. The bimorph is excited with opposite polarity to cause it to bend rapidly in a plane. The light collected from the tip is projected to a small spot on the scanned medium. The bimorph is oscillated by applying an alternating voltage across the piezoelectric elements which causes the bimorph to bend back and forth at high rates. A medium is passed in a direction at least partly orthogonal to the direction of oscillation of the bimorph so that spot, rapidly sweeping across the surface of the medium, scans the surface. To write information on the medium, a source sufficiently intense, is modulated and applied to the fiber. To read information, a sufficiently intense source is continuously applied to the fiber and a detector used to pick up light returned from the medium surface.

Doughnut-like laser beam output formation by intracavity flexible controlled mirror.

Abstract: The formation of the given low loss and large beamwidth doughnut-like fundamental mode of stable resonator by an intracavity flexible mirror is discussed. The mirror is a bimorph one with one round and two ring controlling electrodes. An inverse propagation method is used to determine the appropriate shape of the controlled mirror. The mirror reproduces the shape with minimal RMS error by combining weights of experimentally measured response functions of the mirror sample. The voltages applied to each mirror electrode are calculated. The calculations are carried out for industrial CW CO2 laser.

Inside indicating device for a vehicle

Abstract: The indicating device has a pair of piezoelectric elements (20) fitted to the rim (35) of a steering wheel (13) at diametrically-opposed portions (35a, 35b) gripped by the driver of the vehicle; and a drive unit (22) for driving the piezoelectric elements (20). The piezoelectric elements (20) are bimorph ceramic plate elements of series or parallel type, each have a pair of terminals (21) connected to the drive unit (22), and, when activated, generate mechanical vibrations perceivable by touch and ear by the driver. The drive unit (22) driving the piezoelectric elements (20) generates a first and second alternating-voltage control signal (C1, C2), each of which is applied between a respective pair of terminals (21) of the piezoelectric elements (20), and has a frequency substantially equal to the resonance frequency of the respective piezoelectric element (20).

Application of self-sensing actuator to control of a soft-handling gripper

Abstract: The self-sensing actuator (SSA) is a new concept for intelligent materials, where a single piezoelectric element simultaneously performs as both a sensor and an actuator. This concept is very advantageous in many aspects of control, and it makes it possible to reduce the size and weight of the structures. The bimorph piezoceramics are very useful for the soft-handling miniature gripper to control the minute grasping force. Our aim is to realize such a gripper making the most of the properties of SSA, that is to develop a method to detect the grasping force without a force sensor. The proposed method does not need the complete electric bridge circuit which is generally used to detect the strain information. The experimental result proved that the grasping force provides some desired trajectories irrespective of the rigidity of the grasping object.

Piezoelectric sensors for investigations of microstructures

Abstract: In the paper the application of a piezoelectric bimorph as a sensor to investigate surfaces is considered. The voltage sensitivity and the stiffness of bimorphs with a central metal plate is analysed. This metal plate reinforces the bimorph structure. The derived formulae are used to calculate the parameters of the sensors, which consist of different combinations of metal and ceramic layers. The sensors have been calibrated using the quasistatic method. The experimental results are in good agreement with the calculations. Possible methods for increasing sensor sensitivity are also discussed.

Ciliary microactuator array for scanning electron microscope positioning stage

Abstract: The performance of a ciliary microactuator array as a positioning stage inside a scanning electron microscope is described. Such arrays are attractive because they can provide micron scale positioning resolution with direct electronic control within the sample chamber. The present array uses thermal actuation of a polyimide bimorph to produce long-travel deflection of each cilium and electrostatic actuation to provide a low-power hold-down mode. Each cell in the array consists of four orthogonally oriented cilia which, with proper drive signals, can produce object motion along any direction within the plane of the array. Adapting this array for use inside a scanning electron microscope (SEM) requires only a small mounting block and a modest multiconductor feedthrough. Improved thermal isolation within the vacuum chamber of the SEM drastically reduces the electrical input power requirements over those in air, while still allowing full positioning resolution. The addition of a gold ground plane coating to t...

Bimorph-Type Optical Actuator Using PLZT Elements Position Control of 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 responses of the optical actuator and the shutters, is introduced into the system, and improves the precision and response speed of the optical actuator.

Smart material control system and related method

Abstract: A smart material control system and related method is disclosed for adaptively controlling the movement of an adaptive structure. The adaptive structure includes a smart material layer bonded to a conductive substrate in a bimorph configuration. A charge projector, such as an electron gun, is utilized to project charges onto the smart material layer of the adaptive structure. A voltage/charge source adaptively controls the potential of the conductive substrate. Depending on the placement of the projected charges and the adaptively controlled potential of the conductive substrate the displacement/curvature is precisely controlled. In an alternate embodiment, two smart material layers are bonded together to form an adaptive structure controlled independently in the x- and y- directions. Also, an array of charge projectors and/or conductive substrate sections may be used to provide varying and broad control of adaptive structures.

Bimorph-based piezoelectric air acoustic transducer: model

Abstract: A new type of bimorph-based piezoelectric air transducer with the working frequency range of 200–1000 Hz has recently been developed [B. Xu, Q. Zhang, V.D. Kugel, L.E. Cross, Piezoelectric air transducer for active noise control, Proc. SPIE, 2717 (1996) 388–398]. In the present work, basic acoustic characteristics of this device and its piezoelectric elements are analyzed. To model the vibration spectrum of the transducer, a one-dimensional approach is developed where inertia, elastic and damping forces are included. Analytical equations describing mechanical vibrations and electrical impedance of piezoelectric bimorph cantilevers under external forces are derived. In order to describe various losses in the transducer, complex piezoelectric, dielectric, and elastic constants are used. Results of the modeling are in good accord with experimental data. The suggested model can be used for device optimization.

Self-tuning PID control of a flexible micro-actuator using neural networks

Abstract: A neural network approach to online self-tuning control and real time implementation for a flexible microactuator is presented. The control scheme consists of a gain tuning neural network and a variable-gain PID controller. This neural network is trained to reduce the error between the plant output and reference signal to zero. In the process, the neural network learns the optimal gain of the PID controller. The flexible microactuator is made of a bimorph piezoelectric high-polymer material (PVDF). The bimorph piezoelectric microactuator consists of two PVDF films cemented with a metal shim in proper polarity. Numerical and experimental results indicate that the self-tuning PID neural network control system is effective for accurate trajectory tracking.

Bimorph piezoelectric device for acceleration sensor and method of its manufacture

Abstract: A bimorph piezoelectric acceleration sensor used for sensing the vibration of any of various types of devices such as a hard-disc drive, a CD-ROM drive, etc., which is small in size, high in sensitivity, reduced in variation of sensitivity and low in cost and is produced by grinding a blank of lithium niobate to form a free-vibration part and a support integrally and simultaneously. Two lithium niobate single crystal plates are directly joined to each other in such a way that the directions of polarization are opposite to each other to form a free-vibration part (32a) whose one side is ground to be used as the (32a), while a non-ground part is used as a support (33a), and electrodes (31a and 31b) are formed by electroless plating.

MOEM scan engine for bar code reading and factory automation

Abstract: Rockwell is in the state of technology transfer to manufacturing of a micro-opto-electro-mechanical (MOEM) scan enginewith superior scanning performance for bar code reading and factory automation. The scan engine consists of three maincomponents: actuator, mirrors, and control electronics. The first two components are fabricated on a silicon cantilever beamwhile the control electronics are presently hybrid. The actuator comprises of a bimorph layer covered with two metal layers.The mirror has a large area (several mm2) and it is micromachined with a surface flatness better than X/2. Actuator scan-angles greater than 22° with high repeatability in performance are achieved. The scan engine was integrated with an existingRockwell commercial bar code reader/decoder and successfully proven to read a two-character code 39 bar code. The systemwas capable of decoding the 13-mil label at 360 scans per second with a 100% successful read performance. Environmentaltesting of the device indicates that the scanner can operate at elevated temperatures up to 70°C with minor fluctuations infrequency and scan angle. The scanner has also gone through a lifetime cycle test and it has survived more than 8 billioncycles during a period of 1 8 months. To increase the yield and the performance level of the device, theoretical study as wellas dynamic simulation by finite elements modeling (FEM) have been investigated and will be reported separately.Key words: micro-optics, laser diode, bimorph, optical scanner, microelectromechanical systems, micro-opto-electro-mechanical systems, microlens, bar code reader, object detection, automation

Cooled and uncooled single-channel deformable mirrors for industrial laser systems

Abstract: A study was made of bimorph mirrors intended for industrial laser systems. The technical characteristics of cooled single-channel deformable mirrors were investigated in detail. Preliminary tests were made on uncooled bimorph mirrors in industrial laser systems based on a cw CO2 laser with an output power in excess of 2 kW and on a pulsed copper vapour laser with an average power of 35 W.

Generation device and electronic equipment

Abstract: PROBLEM TO BE SOLVED: To prevent a piezoelectric body or the like from deterioration due to friction and wear by applying a medium to the piezoelectric body in pulse-like manner for vibrating it by a vibration means. SOLUTION: A piezoelectric body 110 is formed into a disk-shaped bimorph type and is provided with electrodes 114 and 115, that are formed on the surface of two piezoelectric plates 112 and 113 adhering to the front and rear surfaces of an intermediate electrode that is connected to a recharging system 180. A vibration means 120 is provided with a medium-giving means 121 and a drive force transfer means 122 for transferring a drive force from a drive system 160. In this case, the vibration means 120 gives a medium to the piezoelectric body 110 in pulse like manner for generating power. Therefore, since the piezoelectric body vibrates due to the non-contact interaction with the vibration means, deterioration due to the friction and wear of the piezoelectric body can be eliminated. COPYRIGHT: (C)1999,JPO

Resonating large-angle and low-consumption micromachined optical scanner

Abstract: A monolithic silicon integrated optical micro-scanner is presented. The device consists of a mirror located an the tip of a thermal bimorph actuator beam. The fabrication process is very simple and compatible with IC fabrication techniques. The device is excited electrothermomechanically at its resonance frequency, enabling large angular deflections at low power consumption. The technological process consists of basic frontside silicon micromachining steps requiring only three mask levels. The moving part is defined by selective silicon bulk etching. The bimorph beam is made of silicon dioxide and a thin film conductor. The residual stress in the two layers is used to achieve a 45 degrees out-of-plane rest position of the mirror. This allows optical components (e.g, laser diode, collimating lens) to be placed directly on the silicon substrate. Mirrors of 500*300 and 1000*500 mu m(2) with resonant frequencies at 300 and 100 Hz respectively were realized. Mechanical scan angles of above 90 degrees were acheived. The devices are very robust and have run through fatigue tests of billions of cycles at 300 Hz and 90 degrees deflection. The power consumption of the device is typically 1mW for 30 degrees mechanical scan angles.

A compact and quick-response dynamic focusing lens

Abstract: A dynamic focusing lens with a completely new mechanism that can be miniaturized and allows for a quick-response has been developed. This lens is structured to directly transform the lens shape as a crystalline lens of the human eye. The lens is comprised of two thin glass diaphragms as a refracting surface, with a transparent working fluid sealed between them, and a new type of piezoelectric bimorph actuator. The displacement of the actuator is enlarged by the bimorph structure. The generated force is determined by the layer number of the bimorph cells. When the actuator is driven to push or pull the glass diaphragm at the actuator side, the other glass diaphragm is transformed into a lens shape (convex lens or concave lens) having various curvatures. The focal length of the lens is controlled by the applied voltage to the actuator. The dynamic focusing lens shows quick response up to 150 Hz. When the lens is operated over 60 Hz, human visual perception cannot recognize the change of the focal length, and we can observe many images having different focal lengths simultaneously.