Fast bender actuators for fish-like aquatic robots
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Small, highly-mobile "swimming" robots are desired for underwater monitoring operations, including pollution detection, video mapping and other tasks. Actuator materials of all types are of interest for any application where space is limited. This constraint certainly applies to the small-scale swimming robot, where multiple small actuators are needed for forward/backward propulsion, steering and diving/surfacing. A number of previous studies have demonstrated propulsion of floating objects using IPMC type polymer actuators [1-3] or piezoceramic actuators [4, 5]. Here, we show how propulsion is also possible using a multi-layer polypyrrole bimorph actuator. The actuator is based on our previously published work showing very fast resonance actuation in polypyrrole bending-type actuators [6]. The bending actuator is a tri-layer structure, in which the gold-PVDF (porous poly(vinylidene fluoride) membrane) substrate was coated on both sides with polypyrrole layers to form an electrochemical cell. Polypyrrole films on gold coated PVDF were grown galvanostatically at a current density of 0.10 mA/cm2 for 12 hours from propylene carbonate (PC) solution containing 0.1 M Li+TFSI-, 0.1 M pyrrole and 1% (w/w) water. The polypyrrole deposited PVDF was thoroughly rinsed with acetone and stored in 0.1 M Li+TFSI- / PC solution. The edges of the bulk film were trimmed off and the bending actuators were prepared as rectangular strips typically 2mm wide and 25 mm long. These actuators gave fast operation in air (to 90 Hz), and were utilised as active flexural joints on the tail fin of a fishshaped floating "boat". The actuators were attached to a simple truncated shaped fin and the deflection angle was analysed in both air and liquid for excitation with +/- 1V square wave at a range of frequencies. The mechanical resonance of the fin was seen to be 4.5 Hz in air and 0.45 Hz in PC, which gave deflection angles of approximately 60° and 55° respectively. The boat contained a battery, receiver unit and electronic circuit attached to the actuator fin assembly. Thus, the boat could be operated by remote control, and by varying the frequency and duty cycle applied to the actuator, the speed and direction of the boat could be controlled. The boat had a turning circle as small as 15 cm in radius and a maximum speed of 2m/min when operating with a tail frequency of approximately 0.7 Hz. The efficiency of the flapping tail fin was analysed and it was seen that operation at this frequency corresponded with a Strouhal number in the optimal range.Keywords:
Polypyrrole
Bimorph
A new bending mode multimorph actuator was designed and fabricated successfully by a multiple screen printing process. Unlike the conventional bimorph actuator in which the bend occurs in the thickness direction, the bend in the multimorph actuator occurs in the widthwise direction because of synchronistical deformation of each single monolithic layer in the multilayer structure. The theoretical analysis and experimental measurements were conducted to study the performance of this type of actuator, and a comparison was made with the conventional bimorph actuator. Larger displacement, higher resonance frequency, and much larger blocking force could be achieved with the multimorph actuator than with a bimorph actuator of similar dimensions. The multimorph actuator presented in this paper provides a valuable alternative for actuator applications beyond those available with the popular bimorph and longitudinal multilayer actuators.
Bimorph
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We are studying a two-axis micro-actuator to enhance the presentation reality of a tactile display that is capable of presenting pressure distribution and shearing force. The actuator is composed of sequentially connected x- and y-directional actuators ; each actuator is comprised of bimorph piezoelectric actuators. The x- and y-directional actuators are independently controlled by changing the applied voltage to position a probe that is attached to the tip of a two-axial actuator. The maximum displacement and force generated by the x-directional actuator are 1.1mm and 0.03N, respectively. Those generated by y-directional actuator are 1.0mm and 0.06N, respectively. Since relationship between applied voltage and displacement caused by the voltage shows a hysteresis loop in the bimorph actuator used as components of the two-axis actuator, we produce a control system for the two-axial actuator based on a multi-layered artificial neural network to compensate the hysteresis.
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Hysteresis
Rotary actuator
Comb drive
Shearing (physics)
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We have developed a cantilever device for applying a time-of-flight scanning force microscope (TOF–SFM) system. The cantilever device consists of a switchable cantilever with an integrated bimorph actuator, an integrated extraction electrode to minimize the ion extraction voltage, and an interlocking structure for precise tip–EE alignment. The TOF–SFM with the cantilever device allows quasisimultaneous topographical and chemical analyses of solid surfaces to be performed in the same way as with the conventional scanning probe technique. The switching properties of the bimorph actuator are demonstrated for use in two operating systems. Field emission measurements and a TOF analysis of a Pt-coated tip are conducted with the TOF–SFM.
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Scanning Probe Microscopy
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The thin and long bimorph cantilever is mechanically responded in motion depending on the position of the heating laser which is focused from the side. The bimorph cantilever was designed in order to detect the heat from a bio cell in liquid. In the calibration process of the cantilever using a focused laser in vacuum and air, we found the quick and interesting responses of bimorph cantilever, which is vibrated and statically deflected due to the position of the local heat source on the cantilever. The deflections of cantilever have been investigated with a developed model. The responses are expressed by the modeled system with heat loss condition into ambient. To define the temperature distributions on the cantilever using a model, the temperature increments at the end of cantilever are successfully estimated to be +20 K in air and +110 K in vacuum with a laser power of 0.17 mW.
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Vacuum chamber
Position (finance)
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Abstract Micro‐cantilevers are excellent tools to measure tiny forces (from 1 nN up to 10 μN) as shown by the development of atomic force microscopy (AFM) techniques. That is the reason why micro‐cantilevers are also the most sensitive acoustic sensors. For instance, one can use the variation of the cantilever's resonant frequency to measure mass loading. In this work, we will show first why diamond is the most suitable material for a special type of cantilever sensors: piezoelectric bimorph cantilever sensors. In contrast to other cantilevers, it is possible to actuate piezoelectric bimorph cantilevers and to detect their resonance frequencies simultaneously. Then, we present one application of this type of cantilever: a diamond/AlN cantilever used as a high pressure sensor (up to 7 ar). The sensor operates by monitoring the frequency shift of the first resonant mode ( f 1 ∼ 36.5 kHz). We have measured a sensitivity of 0.155 Hz/mbar in pure nitrogen. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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Micro-cantilevers are excellent micro-mechanical sensors. In this work, a piezoelectric bimorph cantilever was used as a wide range pressure sensor. Contrary to common cantilever sensor systems, the piezoelectric film of the bimorph cantilever acts as both a sensor and an actuator. The sensor detects the change in the resonance frequency of the micro cantilever with the piezoelectric film. The sensor works as a driven and damped oscillator. Firstly, description and optimisation of the cantilever are discussed in this paper. Secondly, experimental results are described. They show that both pressure and temperature can be measured simultaneously with a piezoelectric bimorph cantilever. I. INTRODUCTION Since the development of the atomic force microscopy, interest in micro-fabricated cantilevers has grown. Micro- machined cantilevers are excellent sensors, they are extremely sensitive and miniature, mass produced and low cost sensors. They operate by detecting changes either in resonance frequency, amplitude, Q-factor or deflection caused by either mass loading, surface stress variation, or any other changes of the cantilever's environment. In the first part of this work, we describe the vibration of a driven and damped simple cantilever and the impedance of a piezoelectric bimorph cantilever. Then, we discuss the optimisation of the piezoelectric bimorph cantilever. In the second part, we present the experimental results of pressure measurements at different temperatures obtained with a commercially available piezoelectric bimorph cantilever. We show it is possible to measure both pressure and temperature with a piezoelectric bimorph cantilever simultaneously.
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Deformable mirrors have gained increasing interest in many different fields of application including laser physics, and they are becoming a universal tool for correcting optical aberrations of laser beams especially in large scale laser systems. One of the most common types of deformable mirror is a bimorph design which uses two plates of piezomaterial to which single electrodes are connected. These electrodes form the actuator array and their layout defines the resulting performance of the mirror to some extent. In the end all types of deformable mirrors currently used use an actuator array of some sort. To estimate the significance and effect of different actuator layout and shapes of actuators, an experimental study was performed. Four different commonly used actuator arrays were compared using photo-controlled deformable mirror. Using such device allows to study the effect of actuator layout separately from all other effects, since the device remains the same including all its imperfections. The experimental results are compared with numerical simulations and discussion is presented.
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Deformable Mirror
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Light-driven polymeric bimorph actuators are being developed as alternatives to prior electrically and optically driven actuators in advanced, highly miniaturized devices and systems exemplified by microelectromechanical systems (MEMS), micro-electro-optical-mechanical systems (MEOMS), and sensor and actuator arrays in smart structures. These light-driven polymeric bimorph actuators are intended to satisfy a need for actuators that (1) in comparison with the prior actuators, are simpler and less power-hungry; (2) can be driven by low-power visible or mid-infrared light delivered through conventional optic fibers; and (3) are suitable for integration with optical sensors and multiple actuators of the same or different type. The immediate predecessors of the present light-driven polymeric bimorph actuators are bimorph actuators that exploit a photorestrictive effect in lead lanthanum zirconate titanate (PLZT) ceramics. The disadvantages of the PLZT-based actuators are that (1) it is difficult to shape the PLZT ceramics, which are hard and brittle; (2) for actuation, it is necessary to use ultraviolet light (wavelengths < 380 nm), which must be generated by use of high-power, high-pressure arc lamps or lasers; (3) it is difficult to deliver sufficient ultraviolet light through conventional optical fibers because of significant losses in the fibers; (4) the response times of the PLZT actuators are of the order of several seconds unacceptably long for typical applications; and (5) the maximum mechanical displacements of the PLZT-based actuators are limited to those characterized by low strains beyond which PLZT ceramics disintegrate because of their brittleness. The basic element of a light-driven bimorph actuator of the present developmental type is a cantilever beam comprising two layers, at least one of which is a polymer that exhibits a photomechanical effect (see figure). The dominant mechanism of the photomechanical effect is a photothermal one: absorption of light energy causes heating, which, in turn, causes thermal expansion.
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Deformable Mirror
Ultraviolet light
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We are studying a two-axis micro-actuator to enhance the presentation reality of a tactile display that is capable of presenting pressure distribution and shearing force. We develop two types of actuators; Actuator A is composed of sequentially connected x- and y-directional actuators; each actuator is comprised of bimorph piezoelectric actuators. The x- and y-directional actuators are independently controlled by changing the applied voltage to position a probe that is attached to the tip of a two-axis actuator. The maximum displacement and force generated by the x-directional actuator are 1.1 mm and 0.03 N, respectively. Those generated by y-directional actuator are 1.0 mm and 0.06 N, respectively. Actuator B is composed of two bimorph actuators making an angle, two small links and three joints. At the present, we confirm that the actuator can move along x and y-axes of two-dimensional coordinate. Finally, since relationship between applied voltage and displacement caused by the voltage shows a hysteresis loop in the bimorph actuator used as components of the two-axis actuator, we produce a control system for the two-axial actuator based on a multi-layered artificial neural network to compensate the hysteresis
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Comb drive
Rotary actuator
Hysteresis
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Abstract The two most common type of piezoelectric actuators are the multilayer actuator with internal electrodes and the cantilevered bimorph actuator[1]. A new type of composite ceramic actuator is the multilayered multistacked moonie (multi-multi moonie). Normal multilayer actuators produce a large generative force, but only a small displacement. Conversely, bimorphs produce large displacements but the forces are very small. The moonie actuator combines the advantages of both, producing a large displacement as well as a reasonably large generative force.
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