Cantilever Actuator Research Articles

727 梁型電磁アクチュエータにおける閉ループ制御と開ループ制御の性能評価(特性解析,OS-23 磁気浮上・磁気軸受,総合テーマ「伝統を,未来へ!」)

727 梁型電磁アクチュエータにおける閉ループ制御と開ループ制御の性能評価(特性解析,OS-23 磁気浮上・磁気軸受,総合テーマ「伝統を,未来へ!」)

Study of Broadband Cryogenic DC-Contact RF MEMS Switches

A dielectric-free DC-contact RF microelectromechanical system (MEMS) switch is designed and tested at room temperature and cryogenic temperatures. The switch demonstrates a 1-? contact resistance and 2 fF up-state capacitance at room temperature, with an insertion-loss less than 0.4 dB up to 50 GHz and less than 0.9 dB up to 75 GHz. The isolation is better than 24 dB up to 50 GHz and 18 dB up to 75 GHz at room temperature. At a cryogenic temperature of 1.6 K, the switch has an insertion loss less than 0.6 dB with isolation better than 24 dB up to 50 GHz. The effects of cryogenic temperatures on deformation of the cantilever beam, actuation voltage, and RF performance have been noted. The theoretical and experimental results of the switch performance are presented and compared.

Current integration force and displacement self-sensing method for cantilevered piezoelectric actuators

This paper presents a new method of self-sensing both of the displacement and the external applied force at the tip of piezoelectric cantilevers. Integrated electric current across piezoelectric actuators is compensated against material nonlinearities (creep, hysteresis) to provide reliable information. We propose to compensate the hysteresis by using the Prandtl-Ishlinskii static approach while an auto regressive and moving average exogenous (ARMAX) model is used to minimize the creep influence. The quasistatic estimation, electronic circuit, and aspects related to long-term charge preservations are described or referenced. As an experiment, we tested the actuator entering in contact with a fixed force sensor. An input signal of 20 V peak-to-peak (10% of maximum range) led to force self-sensing errors inferior to +/-8%. A final discussion about method accuracy and its limitations is made.

Nonlinear analysis of RAINBOW actuator characteristics

This paper discusses an investigation into deformations of rectangular RAINBOWactuators, which are classified as a type of laminated actuator. The actuators consist ofa piezoelectric active layer and a reduced passive layer formed in an elevatedtemperature reduction process. An energy-based Rayleigh–Ritz model is used toapproximate the thermally induced deformations with 23-term polynomials. Due to largeout-of-plane displacements of the RAINBOW actuators after cooling down to roomtemperature, inclusion of geometric nonlinearities in the kinematic relations istaken into consideration. Actuation characteristics of these actuators caused by aquasi-static electric field applied to the piezoelectric layer are also modeled with theRayleigh–Ritz approach. Material nonlinearities in the piezoelectric layer areincluded in the constitutive equation to capture the effects of a strong electric field.Piezoelectrically induced tip deflections of a series of RAINBOW cantilever actuators arecalculated and compared with experiment. With the geometrical and materialnonlinearities taken into account, numerical simulation reveals the computed tipdeflections agree very well with the experimental data. In addition, tip blockingforces representing the load-carrying capability of the RAINBOW actuators areapproximately evaluated by equating the magnitude of force-induced displacementto that of the piezoelectrically induced tip deflection. Again, good agreementbetween numerical results and experiment can be observed in the case of the tipblocking force. This evidently shows that the pertinent nonlinearities have verycrucial effects on the responses and performances of the RAINBOW actuators.

Design, Fabrication, and Operation of Two-Dimensional Conveyance System With Ciliary Actuator Arrays

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, we present the design, fabrication, and operation of a two-dimensional (2-D) microconveyance system. Conceptually, this system was designed as a mechanical part of an autonomous decentralized system composed of integrated micro actuator–sensor–controller cells. The presented system is a 2-D ciliary motion system (2-D CMS) composed of arrayed cantilever actuators. The actuators are made of two types of polyimide with different thermal expansion coefficients. They are thermally driven by flowing current in laminated heaters between the polyimide layers. We investigated the 2-D conveyance characteristics of the 2-D CMS consisting of <formula formulatype="inline"><tex Notation="TeX">$20 \times 20$</tex></formula> cells. Each cell has a pitch of 1420 <formula formulatype="inline"><tex Notation="TeX">$\mu$</tex></formula>m consisting of four actuators of 500 <formula formulatype="inline"><tex Notation="TeX">$\mu$</tex></formula>m in length. The conveyance was performed in a voltage range of 19–32 V, which corresponds to approximately 48–136 mW/cell, in a frequency range of 1–100 Hz, which corresponds to approximately 2–18 <formula formulatype="inline"><tex Notation="TeX">$\mu$</tex></formula>m of minimum step size. We operated it in a feedback control scheme. In feedback operation mode, the 2-D CMS was controlled with a charge-coupled device (CCD) camera regulated by a PC and a programmable logic device (PLD). We succeeded to convey an object to a predetermined target point on the surface of the CMS. </para>

Alignment-tolerant lens structures for acoustic force actuation of cantilevers

In accordance with one aspect of the present invention, a cantilever of a probe-based instrument is deflected by directing a beam of ultrasonic acoustic energy at the cantilever to apply acoustic radiation pressure to the cantilever. The energy is generated by an acoustic actuator. The transmitted beam preferably is focused using a cylindrical lens, providing a beam tightly focused in one dimension and unfocused in a second dimension. In accordance with another aspect of the present invention, a power source such as an RF signal generator is operated so as to spread the spectrum of acoustic radiation on a time scale that is short or comparable to the acoustic roundtrip time. Such a design diminishing the resonance effects and sensitivity to spacing between the cantilever and the acoustic source.

Modeling and optimal design of multilayer thermal cantilever microactuators

A model of curvature and tip deflection of multilayer thermal cantilever actuators is derived. The simplified expression received from the model avoids inverting complex matrices enhances understanding and makes it easier to optimize the structure parameters. Experiment is performed, the modeled and experimental results demonstrate the validity of the model, and it also indicates that Young’s module makes great contribution to the deflection; therefore, thin layers cannot be ignored arbitrarily.

Modeling of Bimorph Type Cantilever for Actuators

A general bending theory for multilayered cantilever with a point load is developed. Based on this theory, a magnetostrictive bimorph type cantilever is modeled for an actuator. The bending and loading characteristics of the cantilever system are discussed systematically, and the optimal conditions, namely the proper balance in choosing the sublayer and substrate thicknesses, as well as material selection, is presented for actuator application. Our discussion may be helpful to the designing and fabricating of the giant magnetostrictive cantilever actuators with more realistic and optimal geometry.

Analysis of functionally graded and laminated piezoelectric cantilever actuators subjectedto constant voltage

Functionally graded and laminated piezoelectric cantilever actuators are investigated. Eachmaterial parameter of the functionally graded actuator can be an arbitrary continuousfunction of the thickness coordinate of the beam, while the property of each layer in thelaminated actuator is uniform. Piezoelectricity solutions for the two actuatorssubjected to a constant electric potential difference are presented. Firstly, the partialdifferential equations for the plane problem of functionally graded piezoelectricmaterials, which govern the stress function and electric displacement function, arederived. Secondly, the stress function is assumed to be an undetermined function ofthe thickness coordinate, and the electric displacement function is assumed asa linear function of the longitudinal coordinate. In such a case, the stress andelectric displacement function can be acquired through successive integrations. Theanalytical expressions of axial force, bending moment, shear force, displacements,electric displacements and electric potential are then deduced. The analyticalsolutions are finally obtained, with the integral constants completely determined fromthe boundary conditions. Comparisons of the present analytical solutions withbeam theory, finite element method and experiments indicate that the analyticalsolutions are effective and exact, while certain deviations of the beam theory can befound.

Innovative Numerical Methods for Nonlinear MEMS:\\ the Non-Incremental FEM vs. the Discrete Geometric Approach

Electrostatic microactuator is a paradigm of MEMS. Cantilever and double clamped microbeams are often used in microswitches, microresonators and varactors. An efficient numerical prediction of their mechanical behaviour is af- fected by the nonlinearity of the electromechanical coupling. Sometimes an addi- tional nonlinearity is due to the large displacement or to the axial-flexural coupling exhibitedin bending. To overcome thecomputationallimitsoftheavailablenumer- ical methods two new formulations are here proposed and compared. Modifying the classical beam element in the Finite Element Method to allow the implemen- tation of a Non incremental sequential approach is firstly proposed. The so-called Discrete Geometric Approach (DGA), already successfully used in the numerical analysis of electromagnetic problems, is then applied. These two methods are here formulated, for the first time, in the case of strongly nonlinear electromechanical coupling. Numerical investigations are performed to find the pull-in of microbeam actuators experimentally tested. The non incremental approach is implemented by discretizing both the structure and the dielectric region by means of the FEM, then by meshing the electric domain by the Boundary Element Method (BEM). A preliminary experimental validationis finally presented in the case ofplanar micro- cantilever actuators.

Radioisotope Thin-Film Fueled Microfabricated Reciprocating Electromechanical Power Generator

A radioisotope power generator with a potential lifetime of decades is demonstrated by employing a 100.3-year half-lifetime 63Ni radioisotope thin-film source to electrostatically actuate and cause reciprocation in a microfabricated piezoelectric unimorph cantilever. The radioisotope direct-charged electrostatic actuation of the piezoelectric unimorph cantilever results in the conversion of radiation energy into mechanical energy stored in the strained unimorph cantilever. The gradual accumulation of the actuation charges leads to the pull-in of the unimorph cantilever into the radioisotope thin-film, and the resulting discharge leads to vibrations in the unimorph cantilever. During the vibrations, the stored mechanical energy is converted into electrical energy by the piezoelectric thin-film. The generator was realized by using both microfabricated lead zirconate titanate oxide-silicon (PZT-Si) and aluminum nitride-silicon (AIN-Si) unimorph cantilevers. The radioisotope direct-charged electrostatic actuation of the AIN-Si unimorph cantilevers by a 2.9-mCi 63Ni thin-film radiating 0.3 muW led to charge-discharge-vibrate cycles that resulted in the generation of 0.25% duty cycle 12.95-muW power pulses (across an optimal load impedance of 521 kOmega) at an overall energy conversion efficiency of 3.97%. These electrical power pulses can potentially be useful for periodically sampling sensor microsystems.

Characterization and Modeling of the Nonlinear Response of Ionic Polymer Actuators

Ionic polymers are compliant, low density materials that operate under low voltage levels as transducers. They can be used as both sensors and actuators for various applications, primarily those involving flexible structures. While some debate continues over the dominant physical mechanisms of actuation, several model forms have been proposed. The majority of these existing models are linear relationships between the applied potential and the strain generated. However, nonlinear characteristics have been observed in both the electrical and mechanical response of cantilever actuators, including harmonic distortion in the sinusoidal time response and a shifting frequency response for increased input levels. Characterization results indicate that the nonlinear mechanisms are dynamic, since they have dominance at low frequencies, but are essentially negligible as the excitation frequency increases. This research uses knowledge gained from the characterization results to develop a dynamic model that can predict the observed nonlinear behavior. The empirical model is constructed from input-output data collected using a Gaussian input current signal and is validated against the measured frequency response function and single-frequency sinusoidal responses. The basic model form has a dynamic nonlinearity on the input to an underlying nonlinear system.

Modelling of the magnetostrictive trilayer cantilever for actuators

The basic mechanical equilibrium equation is employed to model the cantilever system which consists of two giant magnetostrictive films (GMSFs), one with positive and the other with negative magnetostriction, and a non-magnetic substrate (NMS) for actuators. The bending and loading characteristics of the cantilever system are discussed systematically, and the optimal condition for actuator application is presented. The results show that a thicker substrate is favourable for larger force exerted by the cantilever when one of its sublayer thickness is kept constant. But a thinner substrate is required when the total thickness of the cantilever needs to be kept constant so that a proper balance is needed in choosing the sublayer and substrate thicknesses. It is also found that, to obtain the maximum exerted force, the thickness configuration of GMSFs should be fixed at the optimal value. The GMSF/NMS/ GMSF cantilever is generally superior in loading characteristics to the GMSF/NMS and GMSF/GMSF cantilevers. Our discussion may be helpful to the designing and fabricating of the giant magnetostrictive cantilever actuators with more realistic and optimal geometry.

Cantilevered actuator using magnetostrictive thin film

This paper describes a cantilevered magnetic actuator driven by magnetostriction in a low magnetic field. The dimensions of the two layers actuator were 1×5 mm and amorphous FeSiB was used as the magnetostrictive material. Since the FeSiB has excellent soft magnetic characteristics, the actuator with FeSiB was able to work in magnetic field strength of less than 10 kA/m. The theoretical formulas for the amount of the displacement and the force of the actuator were obtained. The theoretical results agreed with the experimental one. According to the theoretical formula, the displacement was calculated with the parameter of the mechanical properties of the substrate. To obtain the large displacement, the actuator with Co substrate was designed based on the theoretical formula. The displacement of 153 μm was obtained using Cu substrate of 1.1 μm thickness in the magnetic field of 10 kA/m. © 2008 Elsevier B.V. All rights reserved

PECVD a-Sic:H Young’s modulus obtained by MEMS resonant frequency

In this paper we study the Young’s modulus of PECVD obtained silicon rich (x>0.5) a-SixC1−x:H thin films through the study of the resonance frequency of free standing cantilevers. These structures are fabricated based on front side bulk micromachining of Si substrate and actuated thermally. In this approach, an alternating electric current passes through a photolithography patterned metallic film deposited on the cantilever, heating the structure by Joule effect and inducing vibrations on the cantilever. This method of actuation is independent of the separation between the structure and substrate, which is its main advantage, because it allows the actuation of cantilevers that are bent upwards or downwards, which is an aspect of particular importance in the characterization of PECVD materials for MEMS applications. The work is focused on low stress silicon rich amorphous hydrogenated silicon carbide films obtained by PECVD at low temperatures (320°C). The measurements were carried out in groups of cantilevers with different length (between 550 and 200μm) and utilizing a-SiC:H films obtained with three different compositions. The results show that the films exhibit modulus of elasticity in the range of 20–35GPa, low residual stress (∼90GPa) and maintain excellent chemical inertness in KOH and HF solutions.

Piezo-actuated nanodiamond cantilever technology for high-speed applications

Diamond cantilever actuators show high resonance frequencies but need also high actuation forces, pointing towards piezoelectric actuation by a PZT/diamond unimorph. In this study lead zirconate titanate (Pb(Zr,Ti)O 3, PZT) layers have been deposited onto nanocrystalline diamond films by sol–gel deposition, to realize high-speed MEMS actuators. The fabrication technology is based on self-aligned patterning and on optical lithography. A mechanical resonance frequency of 3.9 MHz has been obtained for 30 µm cantilever length dominated by the nanodiamond Young's modulus of approximately 1000 GPa.

Variation of atomic spacing and thermomechanical properties in Ni–Mn–Ga/alumina film composites

Ni 51.4Mn 28.3Ga 20.3 thin films deposited on alumina ceramics have been studied by X-ray powder diffraction and dynamic mechanical analysis. Substantial temperature vs. film thickness dependencies of interatomic spacing measured in the direction of the film normal are observed in the range of 25–200 °C and 0.1–5 μm, respectively. The coefficient of thermal expansion (CTE) of the film in the paramagnetic cubic phase has been determined to be equal to (15 ± 1) × 10 −6 K −1 for all the films, in agreement with the CTE of bulk material. The thickness dependent shrinkage of the pseudo-cubic lattice along the film normal direction is attributed to the thermally induced tensile stress in the film plane. The thickness dependence of the elastic modulus of submicron films is obtained. It is shown that the internal stresses result in both the thickness dependence of martensitic transformation temperature and the reversible, thermally induced change in shape of the Ni–Mn–Ga/alumina cantilever actuator.

Electromechanical analysis of electrostatic nano‐actuators using the differential quadrature method

AbstractThe nonlinear analysis of nanoelectromechanical systems using the differential quadrature model is investigated. The differential quadrature method is applied to overcome the difficulty of determining the nonlinear equation of motion. The characteristics of various combinations of curved electrodes and cantilever beams are considered to optimize the design. Various nano‐actuators, such as the cantilever beam actuator, are derived and simulated to examine the feasibility of applying the differential quadrature method to the nonlinear deflection in solving the nano‐actuator problem. The effects of the electrode shapes, the lengths of the actuators, and the moments of inertia of the actuators on the pull‐in behavior of the cantilever actuators in electrostatic nanoelectromechanical systems are investigated. The differential quadrature approach is used to generate the electrostatic field equations in matrix form. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Tip-sample distance control using photothermal actuation of a small cantilever for high-speed atomic force microscopy

We have applied photothermal bending of a cantilever induced by an intensity-modulated infrared laser to control the tip-surface distance in atomic force microscopy. The slow response of the photothermal expansion effect is eliminated by inverse transfer function compensation. By regulating the laser power and regulating the cantilever deflection, the tip-sample distance is controlled; this enables much faster imaging than that in the conventional piezoactuator-based z scanners because of the considerably higher resonant frequency of small cantilevers. Using this control together with other devices optimized for high-speed scanning, video-rate imaging of protein molecules in liquids is achieved.

Single-crystal SiC thin-film produced by epitaxial growth and its application to micro-mechanical devices

This paper deals with the fabrication process of single-crystal silicon carbide (SiC) thin-films and its application to microdevice. SiC thin-film was synthesized using molecular beam epitaxy, where single-crystal SiC layer was grown on single-crystal silicon (Si) substrate. Using lithography and etching process, microscopic cantilevers were fabricated. Typical dimensions of the cantilevers were 10–60 μm in length, 10–30 μm in width, typically 180 nm in thickness. Young's modulus estimated from bending test was almost the same with that of bulk material. Finally, an application is demonstrated where nickel was deposited on the cantilever and biomorphic actuation was carried out. The displacement at the tip was about 2 μm when the temperature change was 40 K. The time constant of the step response was about 0.07 s.