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An interaction through a negative-stiffness spring is introduced into a dual-mass dynamic vibration absorber (DVA) to lower its resonance frequency. DVA is one of the practical vibration control devices. In principles, it consists of an absorption mass and a spring. It can eliminate vibration at a specified frequency that equals the resonance frequency of the DVA. To eliminate low-frequency vibration, it is necessary to increase the absorption mass or lower the spring constant. The former method increases the size of the device and the latter method may cause difficulty in supporting the absorption mass. Although there are reports on the optimal design and robust optimal design of DVAs, there are few reports that focus on lowering the anti-resonance frequency. In addition, there are few studies on the parallel dual-mass DVA that has interference between the vibration absorption masses. This work focuses on parallel dual-mass DVA and proposes to insert a negative spring between the absorption masses. It is analytically shown that one of the resonance frequencies of the DVA can be set lower than that of the conventional DVA. Such characteristics are confirmed by numerical analyses and experiments.

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The vibration isolation system is now indispensable to high-precision instruments and equipment, which can provide a low vibration environment to ensure performance. However, the disturbance with variable frequency poses a challenge to the vibration isolation system, resulting in precision reduction of dynamic modeling. This paper presents a velocity self-sensing method and experimental verification of a vibration isolation system. A self-sensing actuator is designed to isolate the vibration with varying frequencies according to the dynamic vibration absorber structure. The mechanical structure of the actuator is illustrated, and the dynamic model is derived. Then a self-sensing method is proposed to adjust the anti-resonance frequency of the system without velocity sensors, which can also reduce the complexity of the system and prevent the disturbance transmitting along the cables. The self-sensing controller is constructed to track the variable frequency of the disturbance. A prototype of the isolation system equipped with velocity sensors is developed for the experiment. The experiment results show that the closed-loop transmissibility is less than −5 dB in the whole frequency rand and is less than −40 dB around, adding anti-resonance frequency which can be adjusted from 0 Hz to initial anti-resonance frequency. The disturbance amplitude of the payload can be suppressed to 10%.

In this paper author proposed a unique vibration suppression device that has variable inertia mass using continuously variable transmission (CVT) in order to obtain vibration isolation when a harmonic frequency was coincided with an anti-resonance frequency of 1DOF system. The device complies a ball screw mechanism, a flywheel, servo motors and CVT. The CVT is composed of toroidal wheels and power transmission wheels. The device has a small inertia force when an attitude angle of the power transmission is low by the servo motor as depending on a contact radius between two half toroidal wheels, on the other hand the large inertia force under high angle, so variable inertia force which acts as series inertia mass can be controlled continuously. The trial device was manufactured and the resisting force characteristics were measured. Theory of the variable inertia force was introduced, and compared with the experimental results. In order to confirm vibration control, an optimized inertia mass which always adjusts to anti-resonance frequency was determined in case of 1DOF system with the device, frequency response tests were carried out by using a shaking table, and experimental results were compared with calculated ones. Finally, the theory of resisting force and effects of vibration suppression were confirmed.

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The test specimen in environmental vibration test is connected to the fixture through several attachment points. The forces generated by the shaker must be transmitted equally to all attachment points. The forces transmitted to attachment points, however, are different because of the flexural vibration of the fixture. The variations of the transmitted force cause the undertest, especially at anti-resonance frequencies, in vibration test control. Anti-resonance frequencies at the attachment points of the fixture must be same in order to avoid the under-test in vibration test control. The structural modification of the fixture is needed so that anti-resonance frequencies at attachment points have the same value. In this paper, the method to calculate the anti-resonance frequencies and those sensitivities is presented. This sensitivity analysis is applied to the structural modification of the fixture excited at multi-points by the shaker. The antiresonance frequencies at the attachment points of the fixture can have the same value after structural modification, and the under-test in the vibration test control can be removed. Several computer simulations show that the proposed method can remove the under-tests, which are not removed in conventional vibration test control. [ABSTRACT FROM AUTHOR]

Herein, we present a novel method for searching anti-resonance frequencies, using an eigenvalue analysis that does not need to search every dip of amplitude in the frequency response function. The eigenvalue equation is derived by utilizing the fact that the solutions of a forced vibration equation are equal to zero at anti-resonance frequencies. The characteristics of the eigenvalue problem are analyzed with a one-dimensional (1D) bar example, and as engineering applications, four numerical examples are presented to demonstrate the computational efficiency and robustness of the proposed method. • A method for predicting anti-resonance frequencies in vibrating structures is presented. • The method is based on the eigenvalue problem, which is derived from a forced vibration matrix equation. • Characteristics of the eigenvalue problem are investigated using an analytical example. • The results of numerical examples validate the accuracy and efficiency of the presented method. [ABSTRACT FROM AUTHOR]

The vibration isolation system is now indispensable to high-precision instruments and equipment, which can provide a low vibration environment to ensure performance. However, the disturbance with variable frequency poses a challenge to the vibration isolation system, resulting in precision reduction of dynamic modeling. This paper presents a velocity self-sensing method and experimental verification of a vibration isolation system. A self-sensing actuator is designed to isolate the vibration with varying frequencies according to the dynamic vibration absorber structure. The mechanical structure of the actuator is illustrated, and the dynamic model is derived. Then a self-sensing method is proposed to adjust the anti-resonance frequency of the system without velocity sensors, which can also reduce the complexity of the system and prevent the disturbance transmitting along the cables. The self-sensing controller is constructed to track the variable frequency of the disturbance. A prototype of the isolation system equipped with velocity sensors is developed for the experiment. The experiment results show that the closed-loop transmissibility is less than −5 dB in the whole frequency rand and is less than −40 dB around, adding anti-resonance frequency which can be adjusted from 0 Hz to initial anti-resonance frequency. The disturbance amplitude of the payload can be suppressed to 10%. [ABSTRACT FROM AUTHOR]