カンナイ オ リュウドウ スル キュウゲンアツ キエキ ニソウリュウ ノ ケンキュウ

This paper describes a new hybrid vibration suppression technique for flexible structures like beams and plates using piezoelectric elements and analog circuits. There are two main methods to suppress vibration of flexible structures. One is active vibration control and the other is passive vibration suppression. The former is often effective but has a stability problem. While the latter avoids such instability, its controlling force is small. Hence, this paper is proposing a new hybrid vibration suppression method that is stable and effective. The optimum values of the circuit are determined by simple formulations derived by Two Fixed Points Method. The proposed method is verified by experiments that demonstrate that the hybrid method works better than conventional passive vibration suppression methods

A new method for accurately determining the modal equivalent stiffness ratio of bonded piezoelectric structures

This paper describes new methods for measuring the modal equivalent stiffness ratios and modal electromechanical coupling coefficients of piezoelectric elements attached to a host structure such as a beam. Modal equivalent stiffness ratios and modal electromechanical coupling coefficients are essential for estimating the performance and determining an optimum design of active vibration control and passive vibration suppression systems that use piezoelectric elements. Accurate determination of these modal parameters is also useful for other systems including piezoelectric sensors and energy generators. This paper not only describes the measurement methods but also presents the theoretical formulations derived by taking into account the effect of adhesive bonds. The formulations in this paper demonstrate the necessity of experimental measurements and the accuracy enhancements that the theoretical estimations can provide. Conventional methods for obtaining the modal equivalent stiffness ratios are sensitive to measurement errors, which result in the loss of accuracy, rendering these methods unreliable for many practical applications. The proposed methods use an inductor instead of an open circuit to address the abovementioned issue and, thereby, provide significant improvement in the accuracy. Because the loss factors of the experimental apparatus tend to compromise the accuracy of the proposed methods, a method using a negative resistor is proposed, theoretically analyzed, and confirmed to eliminate some of the errors introduced by loss factors. The advantages of the proposed methods and the effectiveness of theoretical analysis, considering the effect of adhesive bonds, are verified experimentally

Optimum tuning of series and parallel LR circuits for passive vibration suppression using piezoelectric elements

Bending vibration of flexible structures can be suppressed passively using piezoelectric electromechanical transducers and optimally tuned LR circuits. Since these systems include both mechanical and electrical elements, the governing equations consist of electrically coupled equations of motion. This paper describes a new method for deriving the governing equations that describe a system’s vibration suppression based on the equilibrium of force principle and using an equivalent mechanical model of a piezoelectric element. Both series and parallel LR circuits are considered in the modeling approach. The optimum values for a mechanical vibration absorber can be formulated by using the two fixed points method. However, exact optimal values for the resistances of the LR circuits have not been formulated in the research literature thus far, and approximate values have been used. Analytical formulations are derived in this paper, and optimum values of the LR circuits are presented, not only in displacement, but also in terms of velocity and acceleration. The effects of the stiffness of the adhesive bond between the host structure and piezoelectric element, the dielectric loss in a piezoelectric element, and the internal resistance of an inductor are considered in the theoretical analysis. The effectiveness of the described analytical method is validated through simulations and experiments

Semi-active vibration isolation system with variable stiffness and damping control

Semi-active systems with variable stiffness and damping have demonstrated excellent performance. However, conventional devices for controlling variable stiffness are complicated and difficult to implement in most applications. To address this issue, a new configuration using two controllable dampers and two constant springs is proposed. This paper presents theoretical and experimental analyses of the proposed system. A Voigt element and a spring in series are used to control the system stiffness. The Voigt element is comprised of a controllable damper and a constant spring. The equivalent stiffness of the whole system is changed by controlling the damper in the Voigt element, and the second damper which is parallel with the other elements provides variable damping for the system. The proposed system is experimentally implemented using two magnetorheological fluid dampers for the controllable dampers. Eight different control schemes involving soft suspension, stiff suspensions with low and high damping, damping on–off (soft and stiff), stiffness on–off (low and high), and damping and stiffness on–off control are explored. The time and frequency responses of the system to sinusoidal, impulse and random excitations show that variable stiffness and damping control can be realized by the proposed system. The system with damping and stiffness on–off control provides excellent vibration isolation for a broad range of excitations

Energy Transfer in a Three Body Momentum Exchange Impact Damper

Special Issue on The Twelfth Asia Pacific Vibration Conference (APVC2007)Impact vibration such as a floor vibration caused by jumping of children or vibration of a press machine is very important engineering problem. The momentum exchange impact damper has been proposed to solve these problems. The basic principle of this damper is based on the energy transfer on collision of three body systems. However energy or momentum transfer at the impact is not explained theoretically. This paper considers the energy transfer incurred during collisions in three body systems. The three body systems considered herein consists of an impact mass, a main body and an absorber mass. When the impact mass collides with the main body, part of its kinetic energy is transferred to the main body. When the main body simultaneously collides with the absorber mass, part of the kinetic energy of the main body is transferred to the absorber mass. Consequently, the main body receives a small amount of shock and it is possible to keep the main body nearly stationary. In this study, the influence of contact frequency and natural frequency of the system on the energy transfer during collision is analyzed. A theoretical model is developed to analyze the effect of various system parameters. It is shown that the maximum transfer of energy that can be obtained occurs when the contact frequencies are the same. The theoretical analysis is validated with experimental results

Application of Momentum Exchange Impact Dampers to Forging Machine

This paper proposes an impact control method for a forging machine using a momentum exchange impact damper. This method is based on momentum conservation of two colliding bodies. A conventional added mass control method fails to suppress the acceleration and force transmission simultaneously. By using the momentum exchange impact damper, it is shown that the bed acceleration and the transmitted force to the floor are reduced. This paper presents a theoretical analysis of an impact damper and an optimum condition that leads to a minimization of the energy of a forging machine. An experimental analysis is shown to validate the simulation results

Reducing Floor Impact Vibration and Sound Using a Momentum Exchange Impact Damper

This paper deals with reducing floor impact vibration and sound by using a momentum exchange impact damper. The impact damper consists of a spring and a mass that is contact with the floor. When a falling object collides with the floor, the floor interacts with the damper mass, and the momentum of the falling object is transferred to the damper. In this works a computational model is formulated to simulate dynamic floor vibration induced by impact. The floor vibration is simulated for various sized damper masses. A proof-of-concept experimental apparatus was fabricated to represent a floor with an impact damper. This example system consists of an acrylic plate, a ball for falling object, and an impact damper. A comparison between simulated and experimental results were in good agreement in suggesting that the proposed impact damper is effective at reducing floor impact vibration and sound by 25% and 63%, respectively

Hybrid Vibration Suppression of Flexible Structures Using Piezoelectric Elements and Analog Circuits

This paper describes a new hybrid vibration suppression technique for flexible structures like beams and plates using piezoelectric elements and analog circuits. There are two main methods to suppress vibration of flexible structures. One is active vibration control and the other is passive vibration suppression. The former is often effective but has a stability problem. While the latter avoids such instability, its controlling force is small. Hence, this paper is proposing a new hybrid vibration suppression method that is stable and effective. The optimum values of the circuit are determined by simple formulations derived by Two Fixed Points Method. The proposed method is verified by experiments that demonstrate that the hybrid method works better than conventional passive vibration suppression methods