強誘電体分極エレクトレットを用いた静電誘導型環境発電の研究

要約のみTohoku University桑野博喜課

Folded Spring and Mechanically Switching SSHI for High Performance Miniature Piezoelectric Vibration Energy Harvester

To downsize the clamp area and increase the output power of the harvester, we developed a miniature piezoelectric vibration energy harvester with combining a Z-shaped folded spring and a mechanically-switching SSHI (synchronized switch harvesting on inductor). The overall harvester size is 4i×2i×3 cm3. The FEM analysis revealed that the output power increases and the value of the 1st and 2nd resonance frequencies move closer as the angle of the Z-shaped spring decreases, therefore, the smaller angle would be more promising. The experimental results showed that the maximum output power of our harvester for the 1st (20.2 Hz) and 2nd (53.0 Hz) resonance frequencies at the applied acceleration of 4.9 m/s2 are 088 and 0.98 mW, respectively. The reason for a marked enhancement of the output power for the 2nd resonance frequency is attributed to the vertical movement of the 2nd vibrational mode which applies larger mechanical stress to the piezo ceramic and achieves better electrical contact between the tip of the Z-shaped spring and the spring plunger. © Published under licence by IOP Publishing Ltd

Nonlinear restoring force of spring with stopper for ferroelectric dipole electret-based electrostatic vibration energy harvesters

Previously, we succeeded in developing a new electret [termed a ferroelectric dipole electret (FDE)] having an extremely high electric field using a polarized ferroelectric material. However, the pull-in, in which an oscillator sticks to the FDE under its strong electrostatic force, poses a problem for practical vibration energy harvesters. In this study, we propose use of nonlinear restoring force of a spring with a stopper in order to prevent pull-in for FDE-based vibration energy harvesters. The spring with a stopper was designed using a finite element method (FEM) analysis such that the restoring force of the spring will exceed the electrostatic force of the FDE. The proposed harvester combines the FDE and the spring successfully, and generated electricity without the pull-in. It also showed the highest figure of merit of output power and wide frequency band when compared with other available electret-based vibration energy harvesters. © 2016 Author(s)

Fuzzy Semiactive Vibration Control of Structures Using Magnetorheological Elastomer

In this research, a novel variable stiffness vibration isolator that uses magnetorheological elastomers (MREs) accompanied with a fuzzy semiactive vibration control was developed. Firstly, the viscoelastic characteristics of MREs in shear mode were clarified systematically in order to achieve a mathematical basis for the controller development. Secondly, the fuzzy semiactive vibration control with a strategy based on the Lyapunov theory and dynamic characteristic of MREs was proposed for minimizing the movement of the isolator. In the conventional semiactive algorithm, the command applied current of MRE-based isolator is set at either minimum or maximum value which causes high acceleration and jerk peaks periodically, thus leading to the degeneration of the overall system quality. However, the fuzzy semiactive algorithm presented here is able to produce the sufficient applied current and thus viscoelastic force is desirably produced. The effectiveness of the developed isolator was evaluated numerically by MATLAB simulation and experimentally in comparison with the performances of a passive system and a system with on-off type semiactive controller. The results showed that the developed controller was successful in overcoming the disadvantages of conventional on-off semiactive control. © 2017 Xuan Bao Nguyen et al

Effects of beta-adrenergic blocking agents on specific binding of [3H]D-Ala2-Met5-enkephalinamide and [3H]naloxone.

To gain further insight into the central nervous system (CNS)-action of beta-adrenergic blocking agents (beta-blockers), we examined the effects of various kinds of beta-blockers on opioid receptors (Op-Rs) using radiolabeled receptor assay (RRA). We demonstrated that beta-blockers are competitively bound to Op-Rs in the CNS. Sodium index of beta-blockers in [3H]naloxone binding study indicated that beta-blockers had the mixed agonist-antagonist activity of opiates. The relative potency of beta-blockers in opioid RRA was negatively correlated with their membrane stabilizing activity. Neither beta-blocking activity nor intrinsic sympathomimetic activity was correlated with IC50 values of beta-blockers in opioid RRA. While it is widely accepted that beta-blockers have a tranquilizing activity, a part of the tranquilizing action of beta-blockers may be mediated through Op-Rs in the CNS. Although beta-blockers may have effects on their own receptors (beta-receptors) in the CNS, the more precise mechanisms of central action of these drugs must be further investigated.</p

Modeling and semi-active fuzzy control of magnetorheological elastomer-based isolator for seismic response reduction

金沢大学理工研究域機械工学系In this paper, a magnetorheological elastomer (MRE) based isolator was investigated to mitigate excessive vibrations in structures during seismic events. The primary objectives of this research are to propose a numerical model that expresses viscoelastic behaviors of the MRE and predict operation process of the MRE-based isolator for future design of isolator systems for various technical applications. Despite the simplicity in parameter definition in comparison to the conventional models, the proposed model works efficiently in a wide range of frequencies and amplitudes. The model consists of the following components: viscoelasticity of host MRE, magnetic field-induced property, nominal viscosity as well as high stiffness in low excitation frequency that are modeled in analogy with a standard linear solid model (Zener model), a stiffness variable spring, and a smooth Coulomb friction, respectively. Furthermore, a semi-active fuzzy controller was designed to enhance the performance of the isolator in suppressing structural vibrations. The control strategy was built to determine the command applied current. The controller is completely adequate for handling the nonlinearity of the isolator and works independently with the building structure. The efficiency of the MRE-based isolator was evaluated by the responses of the scaled building under seismic excitation. Numerical and experimental results show that the isolator accompanied with a fuzzy controller remarkably reduces the relative displacement and absolute acceleration of the scaled building compared to passive-off and passive-on cases. © 2017 Elsevier LtdEmbargo Period 12 month

制振合金を利用した動吸振器の開発

金沢大学理工研究域フロンティア工学系If damping alloy is used as structural material, a structure with high damping performance can be produced and its vibration and noise can be reduced. Damping mechanism of the damping alloy is to convert vibration energy into thermal energy. The damping performance of the damping alloy is not as good as it is used in a dynamic damper. This paper proposes a method of enlarging equivalent loss factor of a damping alloy spring by using a negative spring constant and it is confirmed that the equivalent loss factor of a damping alloy cantilever becomes large by the attraction force of magnet used as the negative spring constant. Optimal design of the dynamic damper which consists of the damping alloy cantilever and a pair of magnets is explained. The vibration suppression effect due to the dynamic damper is demonstrated by means of measuring the compliance and the time history response by impact excitation. The vibration suppression effect depends on the vibrational amplitude due to nonlinearity of the attraction force of magnet but can be sufficiently expected in comparison with the case without the dynamic damper

機械スイッチ式非線形回路による振動発電素子の発電量向上と広帯域化

金沢大学理工研究域フロンティア工学系本研究では，振動発電素子の発電量向上と発電可能な周波数の広帯域化を狙い，機械スイッチ式非線形回路を開発した．機械スイッチとして，折り畳みバネ構造を設計し，高発電量化と広帯域化に必要な条件を明らかにした．また，非線形回路を利用した発電素子の性能を予測するため，電子回路と機械振動を連成解析する手法を確立した．解析の結果，非線形回路は発電量の向上を実現するが，一方で，電圧の昇圧により振動を抑制し発電量を下げる場合もあることを明らかにした．従来の電気スイッチと機械スイッチの性能比較をシミュレーションと実験の双方から検証し，電気機械結合が強い素子では機械スイッチが優れた性能を有することを明らかにした．In aiming at both increase in the output power and wider frequency band width in vibration energy harvesters, we proposed a mechanically switching nonlinear circuit. We designed a folded-spring structure for the mechanical switch, and revealed the optimal condition of the structure. Furthermore, we have developed a two-way coupling simulation technique that allows us to evaluate the practical performance of the harvester connected with the nonlinear circuit, alternately solving the simultaneous equation concerning the mechanical vibration and the electrical circuit. The numerical results show that the nonlinear circuit, which boots up the voltage, may suppress the vibrational amplitude and thus decrease the resulting output power. We investigated the performance for the electronic and mechanical switch nonlinear circuits, both numerically and experimentally, and revealed that the output power for the mechanical switch can exceed that for the electronic one in highly coupled harvesters.研究課題/領域番号:16K18039, 研究期間(年度):2015-04-01 - 2018-03-3