Junjiro Onoda

Low-Energy-Consumption Hybrid Vibration Suppression Based on an Energy-Recycling Approach

An innovative method of hybrid vibration suppression using piezoelectric materials is proposed. It combines bang‐bang active vibration suppression and energy-recycling semiactive vibration suppression. The piezoelectric materials are electromechanically coupled and convert mechanical energy into electrical energy and vice versa. With this method, a part of the electrical energy needed for suppressing vibration is obtained from the mechanical energy of the vibrating structures and is efficiently recycled. Furthermore, the actively supplied energy is stored in the transducers and is reused many times for vibration suppression. Therefore, the hybrid method has better performance than the case where the bang‐bang active method and the energy-recycling semiactive method are both used, but independently. The hybrid method saves the actively supplied energy and is thus a low-energyconsumption vibration control. Its effectiveness in suppressing vibrations was proven in numerical simulations and experiments using a 10-bay truss structure. Moreover, a novel method to prevent undesired control chattering is proposed to further save energy supplied from the external source.

A self-sensing method for switching vibration suppression with a piezoelectric actuator

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.

Comprehensive Assessment of Semi-Active Vibration Suppression Including Energy Analysis

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.

Novel Approach to Self-Sensing Actuation for Semi-Active Vibration Suppression

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.

Using tuned electrical resonance to enhance bang-bang vibration control

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.

Some Advances in Energy Recycling Semiactive Vibration Suppression

This paper summarizes some studies performed by the authors 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.

Performance of Simple and Sophisticated Control in Energy-recycling Semi-active Vibration Suppression

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.

Assessment of Electrical Influence of Multiple Piezoelectric Transducers' Connection on Actual Satellite Vibration Suppression

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.

Fuselage panel noise attenuation by piezoelectric switching control

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.

Development status of the MU upper stage motors

Abstract Two types of upper stage motors named KM-D and KM-M are now under development to mate with the M-3SII launch vehicles. In their design have been incorporated several new technologies — an HMX containing HTPB propellant, a pressure cured head-end web grain, a throat plug type aft-end pyrogen igniter, a 15V-3Cr-3Al-3Sn titanium alloy (KM-D) and a carbon fiber-epoxy filament wound (KM-M) case, and an extendible exit cone deployed by helical spring extensor (KM-D). Design features of each motor and their development status are reported.