Tuning of a Piezoelectric Harvester by Means of a Cantilever Spring-Mass System

2018 ◽  
Author(s):  
Alberto Doria ◽  
Cristian Medè ◽  
Giulio Fanti ◽  
Daniele Desideri ◽  
Alvise Maschio ◽  
...  
Keyword(s):  
High Frequency ◽  
Natural Frequencies ◽  
Coupled System ◽  
Vibration Absorber ◽  
Main Resonance ◽  
Dynamic Vibration Absorber ◽  
Mass System ◽  
High Frequency Resonance ◽  
Tip Mass ◽  
Piezoelectric Harvester

The possibility of improving the performance of a piezoelectric harvester by means of a cantilever dynamic vibration absorber (CDVA) is investigated. The CDVA cancels the original mode of vibration of the harvester and generates two new modes. Some prototypes are developed using a mathematical model for predicting the natural frequencies of the coupled system. Impulsive tests were performed on prototypes. Experimental results show that a small CDVA can lower the main resonance frequency of an harvester of the same extent as a larger tip mass. The measured voltage shows also an high frequency resonance peak, which can be exploited for collecting energy. A multi-physics numerical model is developed for performing modal analysis and stress analysis. Numerical results show that the stress inside the piezoelectric material of the harvester with CDVA results smaller than the stress inside the harvester with a tip mass tuned to the same frequency.

scholarly journals Development of Piezoelectric Harvesters with Integrated Tuning Devices

2018 ◽  
Author(s):  
Alberto Doria ◽  
Cristian Medè ◽  
Giulio Fanti ◽  
Daniele Desideri ◽  
Alvise Maschio ◽  
...  
Keyword(s):  
Numerical Model ◽  
High Frequency ◽  
Natural Frequencies ◽  
Strain Analysis ◽  
Coupled System ◽  
Experimental Results ◽  
Main Resonance ◽  
Modes Of Vibration ◽  
Tip Mass ◽  
Piezoelectric Harvester

The possibility of improving the performance of a piezoelectric harvester by means of novel tuning devices integrated with the harvester’s structure is investigated. Some prototypes of harvesters with tuning devices are developed by mounting cantilever dynamic absorbers on standard harvesters. A mathematical model is used for predicting the natural frequencies of the coupled system. Tests on prototypes are carried out with an impulsive method. Experimental results show that a small tuning device can lower the main resonance frequency of a piezoelectric harvester of the same extent as a larger tip mass and moreover generates at high frequency a second resonance peak. A multi-physics numerical model is developed for predicting the generated power and for performing stress-strain analysis of harvesters equipped with Integrated Tuning Devices (ITDs). The numerical model is validated on the basis of experimental results. Several configurations of ITDs are conceived and studied. Numerical results show that harvesters with ITDs are able to generate relevant power at two frequencies owing to the particular shape of the modes of vibration. The stress in the harvesters with ITDs is smaller than the stress in the harvester with a tip mass tuned to the same frequency.

scholarly journals Adaptive vibration control of the electromagnet-track coupled high frequency resonance for an urban maglev system

2018 ◽  
Vol 4 (2) ◽  
pp. 92-106 ◽  
Author(s):  
Danfeng Zhou ◽  
Peichang Yu ◽  
Jie Li ◽  
Peng Cui ◽  
Mengxiao Song
Keyword(s):  
Vibration Control ◽  
Adaptive Filter ◽  
High Frequency ◽  
Control Algorithm ◽  
Coupled System ◽  
Maglev Train ◽  
Frequency Resonance ◽  
Special Cases ◽  
High Frequency Resonance ◽  
Adaptive Vibration Control

This paper is a study of the electromagnet-track coupled high frequency resonance that frequently occurs in the urban maglev systems, it includes the following points: Aim: The purpose of this study is to investigate the principle underlying the high frequency resonance occurs between the maglev train and the track, and to develop an appropriate vibration control algorithm which can be applied in the levitation controller, such that the resonance can be eliminated when the maglev train travels along the track. Materials and methods of the studies: In this paper, the model of the electromagnet-track coupled system is firstly established, in which some special cases, which correspond to the situations when the screws that fasten the F-rail to the sleepers are fatigue, or the stiffness of the rubber plates beneath the sleepers weaken for temperature reasons, are studied; and the reason that leads to the coupled resonance are explained as well. Secondly, an adaptive vibration control algorithm, which consists of a vibration observer and a tunable adaptive filter, is designed to suppress the high frequency electromagnet-track coupled resonance. Results: Using this algorithm, when the train arrives at the spots where the coupled resonance may occur, the vibration observer will detect the occurring of the vibration and estimates its frequency, and then activate the adaptive filter and tune it to absorb the vibration. Conclusion: The test indicates that this algorithm is capable of tuning itself to handle the unpredictable coupled resonance that occurs along the track, and it is simple and can be easily integrated into the levitation control code in a digital levitation control system.

Exact Frequency Analysis of a Rotating Cantilever Beam With Tip Mass Subjected to Torsional-Bending Vibrations

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Masoud Ansari ◽  
Ebrahim Esmailzadeh ◽  
Nader Jalili
Keyword(s):  
Frequency Analysis ◽  
Time Domain ◽  
Natural Frequencies ◽  
Equations Of Motion ◽  
Bending Vibrations ◽  
Resonant Condition ◽  
Mass System ◽  
Coupled Equations ◽  
Tip Mass ◽  
Gyroscopic Systems

An exact frequency analysis of a rotating beam with an attached tip mass is addressed in this paper while the beam undergoes coupled torsional-bending vibrations. The governing coupled equations of motion and the corresponding boundary condition are derived in detail using the extended Hamilton principle. It has been shown that the source of coupling in the equations of motion is the rotation and that the equations are linked through the angular velocity of the base. Since the beam-tip-mass system at hand serves as the building block of many vibrating gyroscopic systems, which require high precision, a closed-form frequency equation of the system should be derived to determine its natural frequencies. The frequency analysis is the basis of the time domain analysis, and hence, the exact frequency derivation would lead to accurate time domain results, too. Control strategies of the aforementioned gyroscopic systems are mostly based on their resonant condition, and hence, acquiring knowledge about their exact natural frequencies could lead to a better control of the system. The parameter sensitivity analysis has been carried out to determine the effects of various system parameters on the natural frequencies. It has been shown that even the undamped systems undergoing base rotation will have complex eigenvalues, which demonstrate a damping-type behavior.

Theoretical Upper and Lower Bounds of the Performance of an On-Off Damping Dynamic Vibration Absorber Attached to a Multi-Degree-of-Freedom System

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
La Duc Viet ◽  
Phan Thi Tra My
Keyword(s):  
Lower Bounds ◽  
Harmonic Excitation ◽  
Upper And Lower Bounds ◽  
Vibration Absorber ◽  
Amplitude Curve ◽  
Dynamic Vibration Absorber ◽  
Mass System ◽  
Variable Function ◽  
Frequency Curves ◽  
Damping Controller

This paper reveals the theoretical (upper and lower) bounds of the performance of an on-off damping vibration absorber attached to an undamped multi-degrees-of-freedom (MDOF) system under harmonic excitation. The solution reduces to the maximization or minimization problem of a simple single-variable function. Among the class of on-off damping controller, which switches the damping level from high to low and back at fixed times every half period, the revealed solutions produce the highest and lowest amplitude–frequency curves. These curves are the good theoretical benchmarks to measure how good or bad an on-off damping controller is. To demonstrate the usefulness of the theoretical bound solutions, two versions of power flow-driven controller are introduced to produce the amplitude–frequency curves tracing the lowest-amplitude curve. A case study of a four-mass system is discussed.

Vibration of Heavy String Tethered to Mass–Spring System

2017 ◽  
Vol 17 (04) ◽  
pp. 1771002 ◽  
Author(s):  
C. Y. Wang ◽  
C. M. Wang ◽  
R. Freund
Keyword(s):  
Natural Frequencies ◽  
Equation Of Motion ◽  
Gantry Crane ◽  
Vibration Absorber ◽  
Dynamic Vibration Absorber ◽  
Tower Crane ◽  
Spring System ◽  
Mass Spring ◽  
First Time ◽  
Top Mass

This paper is concerned with the vibration of a heavy string tethered to a mass–spring system which is a model for tower crane or gantry crane. The governing equation of motion of the aforementioned problem is solved analytically and exact closed-form characteristic solutions for the natural frequencies are presented. These exact solutions would serve as benchmarks for models which may be more complex than the basic vibration problem considered. Moreover, we investigate the effect of the string-mass pendulum as a flexible dynamic vibration absorber. Such a problem is important in vibration control, and is investigated analytically for the first time. It is found that the effect of the bottom mass is to decrease the amplitude of the string in general. The effect of increased forcing frequency increases the number of nodal points on the string. In most cases, the amplitude of the top mass is reduced.

Theory for an Active Dynamic Vibration Absorber

1991 ◽  
Author(s):  
L. S. Stephens ◽  
K. E. Rouch ◽  
S. G. Tewani
Keyword(s):  
Closed Form Solution ◽  
Control Element ◽  
Vibrational Amplitude ◽  
Vibration Absorber ◽  
Vibration Absorbers ◽  
Lumped Mass ◽  
Dynamic Vibration Absorber ◽  
Mass System ◽  
Dynamic Vibration ◽  
The Impact

Abstract Research in dynamic vibration absorbers has yielded several fundamental designs. Among these are the tuned dynamic absorber, the Lanchester damper, and the impact damper. These designs utilize certain combinations of passive mechanical elements (springs and dampers) to reduce the vibrational amplitude of a system. However, with recent advances in motion sensing and actuating, the design of vibration absorbers that utilize actively actuated elements has become more attractive. This paper develops the theory for using a damped dynamic vibration absorber with an active control element to reduce the vibrational amplitude of a lumped mass system. A control law consisting of a linear combination of velocity and acceleration of the main mass is developed for the active element A closed-form solution is presented for the absorber tuning equation, and numerical methods are used to generate performance curves.

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