1,721,222 research outputs found
An acoustic transformer composed of horns and its application
No full textA new acoustic transformer was developed by connecting three horns to improve radiation performance in the frequency region below 500 Hz. The proposed acoustic transformer was evaluated by numerical analysis using the commercial computer program SYSNOISE and by experiment. The acoustic transformer is composed of three horns, one of which was used in an inverted form. A design model was developed by use of Webster's horn equation and showed that the transformer can improve radiation efficiency. This was confirmed by numerical calculation using SYSNOISE. An acoustic projector was designed by use of the developed transformer and a piezoelectric unimorph-type actuator. The sound pressure measured at the mouth of the constructed acoustic projector was compared with the sound pressures evaluated at the same location by numerical calculation to investigate the differences between the numerical simulation model and the actual acoustic projector. Sound pressures generated by several acoustic radiators were calculated numerically and compared with the measured and calculated sound pressures of the developed acoustic projector to evaluate the effects of use of the proposed acoustic transformer. The comparative evaluation shows that the proposed acoustic transformer can provide up to a 10 dB gain over use of a horn in the narrow band low-frequency region from 100 to 200 Hz. (C) 2002 Elsevier Science Ltd. All rights reserved.X112sciescopu
Hysteresis compensation of piezoelectric actuators: The modified Rayleigh model
No full textIn this study, we develop a novel modified Rayleigh model for hysteresis compensation in piezoelectric actuators. Piezoelectric actuators suffer from hysteresis, in large drive fields of more than 100 V, which can result in serious displacement errors. The typical phenomenological approach is to use the Rayleigh model; however, this model gives more than 10% difference with experiments at the large electric fields of more than 1 kV/mm. Furthermore, there are no studies that apply the Rayleigh model to the compensation of precision actuators, such as stack actuators; it has only been applied in the study of the physical properties of piezoelectric materials. Therefore, we propose a modified Rayleigh model, in which each coefficient is defined differently according to whether the field is increasing or decreasing to account for asymmetry at the high fields. By applying a computer-based control from an inverse form of this modified Rayleigh model, we show that we can compensate for hysteresis to reduce the position error to less than five percent. This model has the merits of reducing complicated fitting procedures and of saving computation time compared to the Preisach model. Specifically, this model cannot only predict the hysteresis curves in all local fields using only one fitting procedure, but also make it possible to control the displacement of various piezo-based actuators without expensive sensors, based on the charge-based model. (C) 2009 Elsevier B. V. All rights reserved.X11713sciescopu
A Micro-Pull-Off Test Machine for Reliable Measurement of Adhesive Forces on Micro/Nano-Scale Areas
No full textIn this study, a micro-pull-off testing machine is developed for reliable measurement of the adhesive force on micro-and nano-scale contact areas. The measuring scheme and working principle of the equipment are based on a reliable measurement technique that uses a commercial atomic force microscope (AFM). Adhesive-force-only measuring equipment is manufactured to overcome the inherent limitations of commercial AFMs, and an adhesive force map with a 1-mu m interval is obtained around a micro-machined pattern of radius 2.25 mu m. Use of the proposed technique and equipment could reduce deviations of the measured bond strength of an adhesive protein compared with those we have previously reported. Moreover, the proposed technique and equipment could be further developed to measure the binding force of even a single molecule if a nano-scale pattern is fabricated.X1132sciescopu
A hybrid-type micro-gripper with an integrated force sensor
No full textA new hybrid-type micro-gripper that uses an integrated force sensor to control the gripping force was developed for handling micro-objects. The micro-gripper is composed of a piezoelectric multilayer bender for actuating the gripper fingers, silicon fingertips fabricated by use of silicon-based micromachining, and supplementary supports. The micro-gripper is referred to as a hybrid-type micro-gripper because it is composed of two main components: micro-fingertips fabricated using micromachining technology to integrate a very sensitive force sensor for measuring the gripping force, and piezoelectric gripper finger actuators that are capable of large gripping forces and moving strokes. A systematic design approach was applied to the design of each of components of the developed gripper, which made it possible to establish the functional requirements and design parameters of the micro-gripper. The micro-gripper was installed on a manual manipulator to assess its performance in tasks such as moving micro-objects from one position to a desired position. The gripping force signal was found to have a sensitivity of 667 muN/V and several micro-objects were successfully moved (grasped and released) with the developed gripper. It was found during the testing experiments that the frictional forces between the working plane and the micro-object could be utilized to facilitate the release of micro-objects from the micro-gripper.X1128sciescopu
A new linear encoder-like capacitive displacement sensor
No full textIn this paper, a new encoder-like capacitive sensor filled with dielectric material is proposed for measuring relatively long range displacements with high accuracy regardless of the gap alignment of the sensor. The proposed sensor consists of two plates with zigzag-shaped electrodes coated with thin dielectric films. When one substrate slides over the other, long range displacements can be measured with high accuracy because variation in the capacitance in one period is measured with high accuracy and repeated signals are counted, as is done in linear encoders. Moreover, the thin and uniform nature of the dielectric layer on each sensor plate means that the proposed sensor is highly sensitive and stable against misalignments such as tilting. Through experimental tests, it is demonstrated that the proposed sensor can measure displacements of up to 20 mm with a resolution of about 126 nm. (C) 2006 Elsevier Ltd. All rights reserved.X1117sciescopu
Electrode configuration method with surface profile effect in a contact-type area-varying capacitive displacement sensor
No full textThe contact-type linear encoder-like capacitive displacement sensor (CLECDiS) is an improved comb-type displacement sensor for high resolution. The sensor displays significantly improved sensitivity without a reduction in the measurable range. This improvement is achieved by maximizing the capacitance variation in response to displacement by reducing the single electrode size, increasing the number of electrodes, and reducing the gap with a contact mechanism in the comb-type sensor. However, owing to the improved sensitivity of the sensor, its output signal is affected considerably by certain geometrical non-idealities such as fabrication errors, which are negligible in traditional capacitive displacement sensors with a single electrode and a relatively large gap. Although the effect of such non-idealities can be minimized or compensated by employing an appropriate filter or differential operation, these solutions cannot deal successfully with effects due to the surface profile of the sensor. During operating of the sensor, this profile causes gap variation, which in turn causes drift in the output signal. This drift is difficult to compensate because it depends on the displacement and the low-frequency component caused by the actual gap variation. In this study, a compensation method is presented to minimize the effects due to non-idealities of the surface geometry of the sensor using electrode configuration. Furthermore, the effect of non-idealities on the capacitance of the sensor is analyzed. The analyzed results are used to present a configuration method based on a widely used differential operation. Finally, the method is tested and compared for sensors based on the normal and proposed configurations. (c) 2012 Elsevier B.V. All rights reserved.X111112sciescopu
The systematic design and fabrication of a three-chopstick microgripper
No full textIn this study, we constructed a new type of gripper for micron-sized objects using piezoelectric multi-layer benders. This new gripper is composed of three chopsticks: two are designed to grip micro-objects, and the third is used to help grasp and release the objects. It is well known that a micro-object is much easier to grasp than to release. Electrostatic, van der Waals forces and surface tension between the chopsticks and object are believed to be the main causes of adhesion. We introduced a third auxiliary chopstick to overcome these surface effects and to reduce the electrostatic forces between the object and chopsticks. All three chopsticks were made of tungsten wires with ends sharpened by etching, which minimises the van der Waals effect. We constructed a three-chopstick gripper for micro-objects and tested its functionality by holding and releasing a 100-micron diameter object. The experiment showed that the third auxiliary chopstick functions effectively.X117sciescopu
Moon, W H (William Hinton), NX55699
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/405791Surname: MOON. Given Name(s) or Initials: W H (WILLIAM HINTON). Military Service Number or Last Known Location: NX55699. Missing, Wounded and Prisoner of War Enquiry Card Index Number: 39824.246522
Item: [2016.0049.38068] "Moon, W H (William Hinton), NX55699
A new transduction mechanism for hydrophones employing piezoelectricity and a field-effect transistor
No full textIn contrast to the induced charge or voltage in conventional piezoelectric hydrophones, changes in the bound surface charge density and the corresponding changes in the electric field from a piezoelectric body do not depend on the size of the piezoelectric material. In this paper, we describe a new transduction mechanism, the piezoelectric gate on a field-effect transistor (PiGoFET), for applications in hydrophones. We describe a theoretical model of the PiGoFET, which shows that high sensitivity can be achieved with a small hydrophone due to the size independence of the PiGoFET transduction mechanism. A PiGoFET hydrophone was designed, fabricated, and characterized. The measured sensitivity was -175.5 +/- 1 dB (Ref. V/mu Pa) at frequencies in the range 50-500 Hz. The measured frequency response was in agreement with the simulated data to within 2 dB. These results demonstrate potential applications in hydrophones, especially for wide-band and low-frequency applications, as well as in micro-hydrophones. (C) 2015 Elsevier B.V. All rights reserved.1155sciescopu
A micro-machined hydrophone employing a piezoelectric body combined on the gate of a field-effect transistor
No full textWe report a micro-machined hydrophone using piezoelectric gate on a field-effect transistor (PiGoFET), where a piezoelectric body is combined directly on the gate of a FET. The PiGoFET transduction mechanism decouples the sensitivity from the dimensions of the piezoelectric body, enabling the miniaturization of hydrophones. Here we exploit the PiGoFET mechanism for hydrophone miniaturization, which is realized via hybrid bonding integration to fabricate a micro-PiGoFET in a CMOS-compatible manner. The hybrid bonding integration employs separate wafers for the piezoelectric MEMS and CMOS processes, which are combined via eutectic wafer bonding to complete the micro-PiGoFET device. A micro-PiGoFET hydrophone was designed, fabricated and characterized with a measured sensitivity of -191.5 dB +/- 11 dB (Ref. V/mu 2a) for frequencies in the range 50-1000 Hz. These results demonstrate the potential for high-performance miniaturized hydrophone systems for wide-band and low-frequency applications, as well as system-on-chip functionality. (C) 2015 Elsevier B.V. All rights reserved.114sciescopu
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