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This study intends to achieve simultaneous vibration suppression and energy harvesting using a variant form of nonlinear energy sink (NES). The proposed apparatus is not a true NES as its spring is not essentially nonlinear. In a previous study [22] (Journal of Sound and Vibration, 333 (20) (2014)), it has been shown that the apparatus demonstrates the transient behaviors similar to those of the NES. As a sequel, the present paper focuses on harmonically forced responses of the system. First, the approximate solutions of steady state responses are derived. Using the approximate solutions, the steady state behaviors are investigated by using the numerical continuation method. This is followed by an experimental study. The study has shown that under harmonic excitation, the proposed apparatus functions similarly to the NES with the typical behaviors such as strongly modulated responses, amplitude jumping, excitation level dependence, etc. Overall, the apparatus meets the design objectives: the vibration suppression and energy harvesting in a broadband manner. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates energy harvesting using nonlinear energy sink. First a novel apparatus is described in detail outlining how the essential nonlinearity and energy harvesting are achieved. Then the system modeling is addressed, including the equations of motion for the mechanical system and the electromechanical system, and a formula for the transduction factor. The experimental identification is conducted to determine several key parameters and relationships. Using the established models, a computer simulation is carried out to investigate the apparatus׳s performance under transient responses in terms of vibration absorption and energy harvesting. Finally experiments are conducted to validate the simulation results. It is shown that the system performs well, being capable of energy localization as well as broad band vibration absorption. The system is also shown to be capable of harvesting energy. [Copyright &y& Elsevier]

Abstract: This work examines the characteristics of a unique active vibration isolator and develops a control strategy for it. The proposed active vibration isolator is introduced and its dynamic model is presented. A characterization study is conducted to identify system parameters. It is shown that with a simple proportional feedback the closed-loop system has a very narrow stability margin due to the inherent dynamics of the actuator. To improve the stability of the closed-loop system and enhance the performance of vibration isolation, a phase compensator is incorporated in the control scheme. An optimization problem is formulated to determine the optimum controller parameters by minimizing the 2nd norm of the displacement transmissibility. Both absolute position feedback and relative position feedback are considered. In real time implementation, an automatic on/off switching strategy is devised to take full advantage of both the active isolator and passive isolator. The experimental results show that with the proposed control scheme, the isolator is capable of suppressing base excitations effectively. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents a newly designed electromagnetic vibration absorber (EMVA), whose stiffness is on-line tunable. The EMVA is capable of suppressing vibration of the primary system excited by a harmonic force with a variable frequency. The EMVA consists of a clamped–clamped aluminum beam and a permanent magnet that is embedded in the center of the beam and placed between two poles of a C-shaped electromagnet. By varying the current of the electromagnet, stiffness of the EMVA can be adjusted instantaneously such that the absorber frequency can be tuned. A detailed characterization of the EMVA is presented. The effective stiffness of the absorber is determined numerically and validated experimentally. To test its effectiveness in vibration suppression, the EMVA is used to track two types of the exciting frequency variations: multi-step and linear. The response of the absorber mass is used to tune the EMVA to ensure that the absorber frequency equals the exciting frequency. [Copyright &y& Elsevier]

In this paper a piecewise linear nonlinear energy sink (PLNES) is developed for the purpose of simultaneous vibration suppression and energy harvesting. The apparatus consists of a cantilever beam attached by a mass at its free end. The beam is situated between a pair of double-stop blocks to constrain its lateral deflection. The stiffness characterization is conducted experimentally. The two combined systems, referred to as weak coupling and strong coupling, are constructed by attaching the PLNES to a stiff primary system and a flexible primary system, respectively. A computer simulation is conducted to investigate the transient performances of the two systems in terms of the targeted energy transfer and energy harvesting. The simulation results are examined by time responses, wavelet transform spectra, and the frequency energy plots. A multi-objective optimization is carried out to investigate the trade-off between vibration suppression and energy harvesting of the two systems. An experimental study is conducted to validate the simulation results. [ABSTRACT FROM AUTHOR]