小野田 淳次郎

Abstract We propose and demonstrate a novel method to enhance vibration harvesting based on surge-induced synchronized switch harvesting on inductor (S³HI). S³HI allows harvesting of a large amount of energy even from low-amplitude vibrations by inducing a surge voltage during the voltage inversion of a synchronized switch harvesting on inductor (SSHI). The surge voltage and the voltage amplification from the conventional voltage inversion improve energy harvesting. S³HI modifies SSHI by both rewiring the circuit without adding components and using a novel switching pattern for voltage inversion, thus maintaining the simplicity of SSHI. We propose a novel switching strategy and circuit topology and analyze six methods that constitute the S³HI family, which includes traditional S³HI and high-frequency S³HI. We demonstrate that the six methods suitably harvest energy even from low-amplitude vibrations. Nevertheless, the harvestable energy per vibration cycle depends on the switching pattern and storage-capacitor voltage. The use of the proposed switching strategy, which allows energy harvesting before energy-dissipative voltage inversion, substantially increases the harvestable energy per vibration cycle. In the typical case considered in this study, the said increase is on the order of 11%–31% and 15%–450% compared to the traditional and existing high-frequency S³HI methods, respectively, depending on the storage-capacitor voltage. Additionally, the proposed circuit can be used as a traditional circuit. It could be considered a promising alternative to S³HI methods owing to its potential auto-reboot capability, which is not found in traditional S³HI circuit.

We report herein our innovative self-powered digital autonomous system for vibration control using a digital micro-processor. Our unit is a completely self-powered control system that does not require an external power-supply. Because this digital, self-directive, self-powered system is programmable and can be used to implement versatile control schemes. Our digital-autonomous controller is much more advanced and progressive than conventional analog-autonomous controllers. Moreover, our digital system can be implemented in multiple-input multiple-output systems (MIMO) to suppress even complicated structural vibrations. This is quite useful for energy-saving or energy-shortage systems, such as large space structures, artificial satellites, and isolated lunar bases, which are vulnerable to long night-time exposures without solar power. Experiments demonstrate that displacement is reduced to as much as 35%. Energy dissipation in experiments is measured using various methodologies. Finally, we investigate the influence of the voltage offset of the AD port of the microprocessor on both estimation error and suppression performance.

We propose a digital autonomous power scavenger with a microprocessor. The proposed system is a completely self-powered one that does not require any external power supply at all, and can thus be used portably at any site. Nevertheless, the digital approach enables the power scavenger to be programmable and thus, it affords some versatility with regard to control schemes. The proposed digitalautonomous system is much more advanced and progressive than clumsy analog-autonomous ones. It can be implemented in multiple-input multiple-output systems to scavenge electrical power from even complicated structural vibrations. We determined the value of the storage capacitance that gives the best balance between scavenging power and consumed power.

We conduct comprehensive investigation of a semiactive vibration suppression method using piezoelectric transducers attached to structures. In our system, piezoelectric transducers are connected to an electric circuit composed of the diodes, an inductance, and a selective switch. Our method (SSDI) makes better use of counterelectromotive force to suppress the vibration, instead of simple dissipation of vibration energy. We use an actual artificial satellite to verify their high performance compared to conventional semi-active methods. As a consequence, we demonstrate that our semi-active switching method can suppress the vibration of the real artificial satellite to as much as 50% amplitude reduction. In our experiment, we reveal that the suppression performance depends on how multiple piezoelectric transducers are connected, namely, their series or parallel connection. We draw two major conclusions from theoretical analysis and experiment, for constructing effective semi-active controller using piezoelectric transducers. This paper clearly proves that the performance of the method is the connection (series or parallel) of multiple piezoelectric transducers and the their resistances dependent on frequency.

Passive damping augmentation is one of attractive methods for vibration suppression to various kinds of structures because it is definitely stable and generally simple. Using viscous adhesive indicated a remarkable effect to the vibration suppression in the practical application to a satellite. In this paper, mathematical model of thin viscous adhesive layer using non-linear elements has been proposed. In this model, the characteristics of elements are correlated with non-linear internal phenomena of polymer. The simulation results using this proposal model are good agreement with experimental ones.

Adhesive bonding structure around a metalic mouthpiece of a cryogenic composite tank was analyzed based on fracture mechanics. Energy release rate was analytically formulated considering difference in strain energies in tension and bending between before and after the crack growth based on a simplified mathematical model. The analytical results were compared with the calculated results by finite element method for five example tanks; they revealed fairly good match. This analysis gives a guideline of the initial optimal design of a cryogenic composite tank based on fracture mechanics.

A novel control law based on the sliding-mode control is proposed for energy-recycling vibration suppression of a structure with piezoelectric transducers. The performance of vibration suppression with the proposed control law is investigated and compared with that of the previously proposed control law based on LQR control theory. Numerical simulations of vibration suppression with a 10-bay truss structure show that the proposed control law is effective in suppressing vibration. Through experiments of vibration suppression with a truss structure, the proposed control law is shown to suppress single-mode and multiple-mode vibrations of actual structure. Although the proposed control law is derived in a different way from the previous control law, the two methods are found to have similar coefficients of modal velocities in the control index.

Passive damping augmentation is one of attractive methods for vibration suppression to various kinds of structures because it is definitely stable and generally simple. The system using thin film with viscous adhesive indicated a remarkable effect to the vibration suppression in the practical application to a satellite. To investigate its damping characteristic, several kinds of experiments have been performed. The results show that the non-linear behavior cause of non-Newtonian flow between shear load and shear deformation velocity in the viscous lamina of the thin film contributes to the damping capability. A mathematical model which consists of spring elements as film and friction elements as viscous lamina has been proposed from experiments. The simulational results with this present model are in good agreement with experimental ones.