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.

This article describes the optimal configuration and combination of piezoelectric transducers and inductors for the synchronized-switch-damping-on-an-inductor technique. The technique suppresses structural vibrations by inverting the polarity of the electric voltage in a piezoelectric transducer using a switched inductive shunt circuit at each displacement extremum. The energy dissipation rate of synchronized switch damping on an inductor depends on the impedances of the transducer and the inductor in the circuit, especially the resistive component, in this inversion. For this study, mathematical models of the equivalent resistances of transducers and inductors for this inversion phenomenon were formulated based on experiments with various transducers and inductors. Using these models, the optimal ratio of the thickness-area of patch-type piezoelectric transducers and that of the length-cross-sectional area of the lead of the inductors were analytically obtained. The optimization of series-parallel connections of multiple transducers and inductors was also shown to be equivalent to this one. The optimal mass budget allocation for the transducers and inductors was also formulated. Two examples of optimization, involving an increase in energy dissipation rates by a factor of 4, were presented. The examples showed that the time taken to suppress free vibrations in a clamped beam was reduced to half through the optimization.

The vibration suppression technique called LR-switching or SSDI (synchronized switch damping on inductor) has attracted considerable interest because of its simplicity, robustness, and high performance. Previously, the authors have experimentally demonstrated that this method can reduce the vibration amplitude of 140kg satellite by 50 percent by using 80grams piezoelectric transducers. This vibration suppression method converts structural vibration energy into electrical energy as a charge in the capacitance of the piezoelectric transducers. Then the polarity of this charge or voltage is inverted according to the phase of structural vibration by a switched inductive shunt circuit, so that the piezoelectric transducer generates the right polarity of force to suppress the structural vibration effectively. Although the loss of the electric energy at this voltage inversion dominates the performance of the technique, it was difficult to estimate this loss from design parameters of the transducer and inductor. Recently, the authors established a mathematical model of this energy loss based on experimental data obtained by using various piezoelectric transducers and inductors (eg. IAC-14 C2.P1X22859). This model enables us to estimate the performance of SSDI technique from design parameters. This paper proposes a method of optimization of SSDI system using this model, and demonstrates the benefit brought by the optimization. The optimization maximizes the energy dissipated by the SSDI technique per a cycle of steady state vibration. As an example, a clamped beam is considered, and a SSDI system is optimized to suppress the vibration of the beam. Results of the optimization demonstrate significant enhancement of the damping of the beam due to this optimization.

Many works have been reported on the semi-active vibration suppression technique so called synchronized switch damping on inductor (SSDI). The technique uses a piezoelectric patch attached to a vibrating structure and a switched inductive shunt circuit. At each extermum of the voltage across the piezo patch, SSDI technique turns on the switch of the shunt circuit such that the voltage inverses. When the inversion is completed, the switch is immediately turned off. It is well known that this technique effectively suppresses the vibration of the structure. Previously, the authors have experimentally demonstrated that this method can reduce the vibration amplitude of 140kg satellite by 50% by using 80g piezoelectric patches. In that demonstration, it revealed that multiple piezoelectric patches needed to be attached to the actual satellite structure because of the practical limitation of space where the piezoelectric patches can be attached. It was also shown that the performance in suppressing the vibration heavily depends on the configuration of parallel/series electrical connection of these patches. Therefore, we have studied and shown the optimal parallel/series connection of the patches. This paper shows the optimal configuration of parallel/series connection of not only the piezoelectric patches but also multiple inductors.

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.

A novel invention, a digital self-powered autonomous system, is proposed to achieve sophisticated vibration suppression dealing with multimodal vibrations. This vibration suppressor can be used ubiquitously at any site because it does not require an external power supply or a central control authority. The digital approach enables the system to be programmed, and thus, it affords some versatility with regard to control schemes. The proposed system is a vast improvement over conventional analog-autonomous systems whose fine-tuning is very difficult. The digital unit can be implemented in multi-input/multi-output systems to suppress complicated structural vibrations, such as multimodal vibrations. This paper provides an analytical discussion on the energy-harvesting effect on suppression performance in terms of the power balance and flow. Experiments demonstrate that the vibration magnitude reduces dramatically by as much as 79.7% under force excitation, although the self-powered control unit is used.

A reliable and evolvable vibration suppression technique using a digital processor powered by energy harvested from a piezoelectric element was developed and investigated. This technique, called a self-powered digital vibration control, benefits from both the sophisticated control logic of the digital processor and a reliable self-powered semiactive element. A system embodying this technique consists of a circuit outline, CPU, and DC/DC converter. Two experiments emulating the synchronized switch damping on inductor (SSDI) technique demonstrated its effectiveness for steady inputs as well as transient ones. [DOI: 10.1115/1.4005027]

Many researchers have been trying to harvest electric energy from structural vibration for various self-powered small systems. To enhance the harvesting performance self-powered switched shunt circuits have been invented. However, all of these studies have been limited to the energy harvesting form sinusoidal vibrations of a single-degree-of-frcedom (SDOF) structure. In our study, a multiple-degree-of-freedom (MDOF) structure is randomly excited. By using a piezoelectric transducer and a rectifier, electrical energy is taken out from the randomly vibrating structure and stored in a capacitor connected to an electric load. In various conditions, we study how much electrical energy can be stored with and without our switched shunt circuit. Our switched shunt circuit is composed of inductors, resistors, capacitors, diodes, thyristors, and programmable unijunction transistors (PUT), which was originally invented for semi-active vibration suppression. Experimental results show that the stored electrical energy can be increased more than twice with our simple shunt circuit even when the structure is randomly vibrating. Copyright © (2012) by the International Astronautical Federation.

We report herein on how we developed our innovative digital self-powered autonomous system for vibration controller using a digital micro-processor. The invented unit is a completely self-powered control system that does not require any external power-supply at all. Nevertheless, this digital, self-directive, and self-powered approach enables the system to be programmable and thus versatile in control scheme. The digital-autonomous controller is much more advanced and progressive than conventional analog-autonomous ones that are clumsy and awkward. This digital system can be implemented in multiple-input multiple-output systems to suppress even complicated structural vibrations. This is quite useful for various applications to energy-saving or energy-shortage systems, such as large space structures, artificial satellites, and isolated lunar bases, which all are vulnerable to long night-time without solar-power. Experiments demonstrate that displacement is reduced by as much as 35 %, which is quite a striking and attractive number. Energy dissipation in experiments is measured by various cases. Furthermore, we investigate the influence of voltage offset of AD port of the microprocessor both on estimation error and on suppression performance. © 2012 The Japan Society of Mechanical Engineers.

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.

This paper demonstrates various investigations of our innovative vibration suppression method, called "Digital Self-Powered". The vibration is inhibited by properly switching the status of an electric circuit made up of an inductor and a selective switch connected to a piezoelectric transducer, the control logic calculation and the switching is performed by a digital microprocessor that is driven by electrical energy converted from mechanical vibration energy. Therefore, this vibration suppression system runs without any power supply. This feature of "self-powered" makes this method advantageous in various applications. It is known that some analog techniques can also control the status of an electric circuit adequately and suppress monotone vibrations nicely. However, these analog techniques suppress multimode vibration less-effectively. To realize an ideal vibration suppression system that is both self-powered and effective in suppressing multimode vibration, sophisticated control logic is installed in the digital microprocessor that is driven by the energy converted from vibration energy. In this paper, we describe the detail of our self-powered systems, and experimental results of multimodal vibration suppression using self-powered systems. Moreover, experimental results were highlighted in light of its high damping performance and adaptability in various vibrational conditions.

This paper presents a digital self-chargingself-directive system thatachieves sophisticated vibration control. The vibration controller can ubiquitously be usedat any site, because it does not require an external power supply or a central control authority. The digital approach enables the system to be programmed, and thus, it affords some versatility with regard to control schemes. The proposed system is a vast improvement over conventional analog-self-directive systems whose fine-tuning is very difficult. The proposed system is useful for various applications where energy-saving or energy-shortage concerns exist, such as large space structures, artificial satellites, and isolated lunar bases, which all are vulnerable to long night times without solar power.

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.

This paper describes a problem that we encountered in our noise attenuation project and our solution for it. We intend to attenuate low-frequency noise that transmits through aircraft fuselage panels. Our method of noise attenuation is implemented with a piezoelectric semi-active system having a selective switch instead of an active energy-supply system. The semi-active controller is based on the predicted sound pressure distribution obtained from acoustic emission analysis. Experiments and numerical simulations demonstrate that the semi-active method attenuates acoustic levels of not only the simple monochromatic noise but also of broadband noise. We reveal that tuning the electrical parameters in the circuit is the key to effective noise attenuation, to overcome the acoustic excitation problem due to sharp switching actions, as well as to control chattering problems. The results obtained from this investigation provide meaningful insights into designing noise attenuation systems for comfortable aircraft cabin environments.

This paper demonstrates, from viewpoint of electrical connection, comprehensive investigation of a semi-active vibration suppression method using piezoelectric actuators attached to structures. In our system, piezoelectric actuators are connected to an electric circuit composed of diodes, an inductance, and a selective switch. Our method (LR-Switching) makes better use of counter electromotive force to suppress the vibration, instead of simple dissipation of vibration energy. We use an actual artificial satellite to verify their high damping 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 analyses and experiment, for contracting effective semi-active controller using piezoelectric actuators. In this paper clearly proves that the performance of the method is the connection of multiple piezoelectric actuators and the their resistances dependent of frequency. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

This paper demonstrates an innovative invention: "digital self-powered autonomous" vibration-suppressor using a digital micro-processor. Our invented unit is a completely self-powered vibration-suppression unit that does not require any external power-supply at all. Nevertheless, this digital, self-directive, and self-powered approach enables the vibration suppressor to be programmable and thus versatile in control scheme. The digital-autonomous suppressor is much more advanced and progressive than clumsy analog-autonomous ones. This digital system can be implemented in MIMO (multiple-input multiple-output) systems to suppress even complicated structural vibration. To our best knowledge, this invention is the first one in the world, and quite useful for various applications to energy-saving or energy-shortage systems, such as large space structures, artificial satellites, and isolated lunar bases, which all are subject to long night-time. Copyrihgt©2010 by the International Astronautical Federation. All rights reserved.

The purpose of this paper is to propose a new method to reduce the calculation cost of the dynamic relaxation method. The proposed method combines the dynamic relaxation method with a static iterative method via two switching rules. In this method, the numerical scheme used in the analysis is selected as the situation of the analysis. An unstable region of the analysis in which the static iterative method cannot obtain the converged solution is performed by the robust dynamic relaxation method. Then a stable region that is costly to be solved by the dynamic relaxation method is performed by the efficient iterative method. By switching the analysis methods like this, the proposed method can use only the advantages of each method and complement each drawback. The performance of the new method is verified through a comparison of numerical analyses for the wrinkled membrane with the new method and conventional methods.

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

This paper summarizes some studies performed by the author's group on energy-recycling semiactive vibration suppression using piezoelectric transducers embedded in the vibrating structures and shunted on switched inductive circuits. Basic idea of this method is to suppress the vibration by controlling the switch in the shunt circuit, which was first introduced by Richard C., et al. This idea has been upgraded by introducing (1) a multiple-input-multiple-output (MIMO) control method for the switches in the shunt circuits, (2) a self-sensing method to estimate the state of structure from the voltage across the piezoelectric transducer, so that any additional sensors can be neglected, and (3) a self-powered shunt circuit that performs the semiactive vibration suppression without any power supply. Several numerical and experimental results showed that the method works well against transient, sinusoidal, and random multi-modal vibrations and suppresses the vibrations effectively. It was also shown that the method is very robust, and, with it, the system is always stable. Studies for various applications of this method are also discussed.

The semi-active energy-recycling methods studied in this article suppress vibration by controlling switches in inductive shunt circuits connected to piezoelectric transducers in vibrating structures. This article compares the performances of simple and sophisticated methods that can be used for multiple-mode vibration. Although it should be obvious that the performance of the latter is superior, we need to know whether the superior performance of the sophisticated method justifies the expense incurred by its complexity. The performance comparisons were done by numerically simulating the vibration suppression of a truss structure with a piezoelectric transducer. We simulated transient free vibrations, forced sinusoidal vibrations, and forced random vibrations. In all cases, both methods were shown to be effective for the first and second modes of vibration. The ways and situations in which the sophisticated method is superior to the simple method were also elucidated. A vibration suppression experiment using a truss was also carried out and demonstrated that the sophisticated method worked well under random excitation.

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.

This paper discusses a self-sensing vibration suppression method that measures only the value of the piezoelectric voltage. The method separates the electrical status into two cases concerning electrical current and characterizes each of these to establish a self-sensing system using extended system equations and a Kalman filter. Our self-sensing system can avoid estimation blackout during closed-circuit status and lessen harmful influences from residual modes. Experiments revealed that the self-sensing system suppressed vibrations in cooperation with state-switching and synchronized-switching controls. We confirmed that the self-sensing method is robust against model errors in a vibration suppression experiment in which there are model errors caused by an intentional frequency shift.

This novel control logic for a shock absorber using particle-dispersion Electro-Rheological (ER) fluid is a powerful means of shock attenuation for satellite instruments that are subjected to lift-off shock or pyrodevice ignition shock. Satellite instruments may be damaged when the acceleration generated by the input shock exceeds their critical acceleration value. The proposed method attenuates the shock so that the instrument's acceleration does not exceed the critical value, even when the shock is too large to be accepted. In contrast to conventional linear shock controls, the proposed shock control does not attempt to attenuate a small shock in order to prepare for attenuating a coming large shock. This innovative nonlinear control enables the absorber to effectively attenuate a powerful shock. Numerical simulations show that the new shock absorber system attenuates shocks better than a passive system or a conventional linear control system.

We enhanced the bang-bang vibration control by using an electrical resonance mechanism. The bang-bang method is used in many engineering applications because of its simplified hardware configuration in which a constant-voltage supplier is shared by multiple actuators. However, its control performance is restricted, because the supplied voltage is constant and the sharp modulation of the control input induces chattering, which wastes a significant amount of energy. Our approach to overcome these problems was to combine the bang-bang method with tuned electrical resonance. Based on an elaborate analysis of phase relations between mechanical and electrical vibrations, three switching. logics were devised for the hybrid method. Experiments on a 10-bay truss structure demonstrated that our hybrid method not only enhanced vibration suppression of the bang-bang method, but also prevented control chattering.

This paper presents an extensive investigation on the LR-switching method (also called the energy-recycling semi-active method). Compared with the energy-dissipative R-switching method, the LR-switching method has been shown to have significantly better vibration suppression performance. However certain essential issues affecting a system employing the LR-switching method remained to, be dealt with. In particular we had to clarify its vibration suppression mechanism from the viewpoint of mechanical and electrical energy exchange. Second, the robustness of the method against model errors and control time delays had to be verified. The experiments and numerical simulations that we conducted on a 10-bay truss structure demonstrate that the LR-switching method outperforms other suppression methods under sinusoidal and random excitations, which are more common in real systems and more difficult to deal with than transient vibrations. This paper provides fundamental insights on the LR-switching method and gives the method a guarantee for actual applications.

We developed the novel control logic for a shock damper using particledispersion Electro-Rheological (ER) fluid. This is a high-powered means of shock attenuation for satellite instruments that are subjected to lift-off shock or pyrodevice ignition shock. The proposed method attenuates the shock so that the instrument's acceleration does not exceed the critical value, even when the shock is too large to be accepted. In contrast to the conventional linear shock controls, the proposed shock control does not attempt to attenuate a small shock in order to prepare for attenuating a coming large shock.

Experiments of vibration suppression were executed by implementing the energy-recycling semi-active method using piezoelectric transducers. The purpose of the experiment is to practically apply the method, of which performance has been proved numerically and experimentally using the truss model, to an actual satellite structural model and investigate an effectiveness and problems of the practical application. Although the damping performance in the experiments was not so good in comparison with that in the truss model experiments, it was found that the energy-recycling semi-active method worked on an actual satellite model and showed better performance than the conventional semi-active method. The description of the energy-recycling method, the configuration and the results of the experiments are presented. Copyright IAF/IAA. All rights reserved.

The authors have proposed a new spin control method for the spinning solar sail. We have investigated the feasibility of this new method by utilizing a simple analytical model. However, in the past analyses, the cross-sectional deformation of sail membranes is only considered, and the membrane is analyzed with the elastica model. The deformation of membranes in the radial direction and the effects of the wrinkling of membranes are neglected. In this paper, the finite element analysis is performed to investigate the feasibility of the new spin control method in more details. Since the finite element analysis is conducted in the three-dimensional model, the radial deformation of the membrane can be considered. In addition, the effects of the wrinkling on the membrane are also taken into account by conducting the buckling analysis. The quantitative investigation of the effects of the radial deformation and the wrinkling on a spin control torque is discussed through numerical simulations. Moreover, the relation between the control torque and the circumferential stress of the membrane is also described. Copyright IAF/IAA. All rights reserved.

The purpose of this paper is to propose a new method to reduce calculation cost of the Dynamic Relaxation (DR) method. The proposed method combines the DR method with a static iterative method via two switching rules. In this method, the numerical scheme utilizing in the analysis is selected as the situation of the analysis. An unstable region of the analysis in which the static iterative method cannot obtain the converged solution is performed by the robust DR method. Then, a stable region that is costly to be solved by the DR method is performed by the efficient iterative method. By switching the analysis methods like this, the proposed method can utilize only the advantages of each method and complement each drawback. The performance of the new method is verified through a comparison of numerical analyses for the wrinkled membrane with the new method and conventional methods.

A low energy dissipation circuit is proposed to achieve more effective energy harvesting, called 'synchronized switch harvesting on inductor (SSHI)'. The proposed circuit only has two diodes, while the original SSHI circuit has four diodes comprising a diode bridge. It thus reduces the voltage drop during the energy-harvesting process, because the actual diodes have forward voltage regarded as equivalent electrical resistance or energy dissipation. Energy-harvesting experiments demonstrated that the proposed circuit increases the harvested energy output to as much as 120% of that for the original SSHI circuit. We confirmed that the storage voltage in the steady state is independent of the storage capacitance through extensive energy-harvesting experiments, and that the settling time of the storage voltage is proportional to the storage capacitance but independent of the harvesting circuit.

A novel self-sensing method using piezoelectric actuators for semi-active vibration suppression is proposed and investigated. By using extended system equations, this self-sensing method can be implemented with a Kalman filter instead of the conventional bridge circuit technique. The method separates electrical status into two cases concerning electrical current, and characterizes each of these to establish the self-sensing system. This method is applicable to multiple-degree-of-freedom structures with multiple piezoelectric actuators. A numerical vibration suppression simulation demonstrated that the self-sensing method works well on a truss structure and has significant robustness against parameter variations. Experimental results also demonstrated that the self-sensing method suppresses not only single-mode vibration but also multiple-mode vibration.

We conducted various investigations of energy-recycling semi-active vibration suppression by using piezoelectric transducers attached to structures. In this method, the converted electrical energy is recycled to suppress the vibration of structures instead of simply being dissipated. First, the energy-recycling semi-active method was applied to vibration suppression of a beam that is a typical continuous structure. Then, the method was applied to suppress the transient vibration of a membrane that is a typical tension-stabilized structure. Through these investigations, the energy-recycling method was found to be effective for use with various systems. (C) 2006 Elsevier Ltd. All rights reserved.

A momentum-wheel installed to provide attitude-control torque actually produces undesirable force or torque disturbances owing to wheel imbalance and imperfection of the ball-bearings. To improve the pointing performance of observation satellites, a vibration isolator is used to isolate observation devices from these disturbances. This paper compares three types of semi-active isolators that consist of a piezoelectric material and a switch-con trolled passive circuit. Since this isolation is implemented by controlling a circuit switch no external energy is supplied to the system, and so the system is stable even when a malfunction occurs in control. We propose a simple but effective isolation method that needs to know only one velocity value instead of the full state of the system. Numerical simulations with a simple model of an observation satellite demonstrated that the proposed isolator works well to isolate an observation device from disturbances caused by the momentum-wheel, without causing any degradation in the attitude control of satellites.

The aim of this research is to attenuate the acoustic noise transmitted into a rocket faring by using a piezoelectric network. The paper makes two assumptions that faring structures can be deformed by actuation forces, or, not be deformed by them (i.e., easy-to-deform or hard-to-deform cases). We characterize both of these and develop acoustic controls for each. Experiments and numerical simulations demonstrated that our methods attenuated the acoustic level generated not only by simple monochromatic noise, but also broadband noise. Unique Issues concerning the acoustic problem were identified that have not been clearly recognized in the vibration suppression problem. Our attenuation method based on an energy-harvesting technique was shown to be effective for the acoustic problem in realistic hard-to-deform faring structures. Copyright © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

This paper presents a self-sensing method for semi-active vibration suppression that measures only the value of piezoelectric voltage. This self-sensing method is implemented with a Kalman filter with extended system equations, instead of the conventional bridge-circuit technique. The method has several advantages over the bridge-circuit self-sensing method, such as being applicable to MIMO systems. Experiments showed that our self-sensing system suppressed vibrations by combining the state-switching control and the synchronized-switching control. We confirmed that the self-sensing method is robust against model errors through the experiment with intentional frequency shift.

A promising method of hybrid vibration control using piezoelectric transducers and switchable circuits is studied. The hybrid approach improves the control performance of the bang-bang active method, by combining it with energy-recycling approach. A part of the electrical energy needed for vibration control is converted from vibration energy and stored, rather than being provided entirely from external sources. In addition, the method recycles the stored electrical energy many times, by preventing it from being dissipated, thus minimizing energy-consumption. We discuss the spillover energy into uncontrolled vibration modes in the hybrid method. A control-chattering prevention is also presented to avoid unnecessary energy-consumption and to obviate residual mode excitation.

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.