Tuning the Resonant Frequency and Damping of an Electromagnetic Energy Harvester Using Power Electronics
ABSTRACT In order to maximize power density, the resonant frequency of an energy harvester should be equal to the source excitation frequency and the electrical damping set equal to the parasitic damping. These parameters should be adjustable during device operation because the excitation characteristics can change. This brief presents, for the first time, a power electronic interface that is capable of continual adjustment of the damping and the resonant frequency of an energy harvester by controlling real and reactive power exchange between the electrical and mechanical domains while storing the harvested energy in a battery. The advantages of this technique over previously proposed methods are the precise control over the tuning parameters of the electrical system and integrated rectification within the tuning interface. Experimental results verify the operation, and the prototype system presented can change the resonant frequency of the electromechanical system by ±10% and increase the damping by 45%. As the input excitation frequency was swept away from the unmodified resonant frequency of the harvester, the use of the tuning mechanism was shown to increase real power generation by up to 25%. The prototype harvester is capable of generating 100 mW at an excitation frequency of 1.25 Hz.
SourceAvailable from: Han Kyul Joo[Show abstract] [Hide abstract]
ABSTRACT: This work investigates a vibration-based energy harvesting system composed of two oscillators coupled with essential (nonlinearizable) stiffness nonlinearity and subject to impulsive loading of the mechanical component. The oscillators in the system consist of one grounded, weakly damped linear oscillator mass (primary system), which is coupled to a second light-weight, weakly damped oscillating mass attachment (the harvesting element) through a piezoelastic cable. Due to geometric/kinematic mechanical effects the piezoelastic cable generates a nonlinearizable cubic stiffness nonlinearity, whereas electromechanical coupling simply sees a resistive load. Under single and repeated impulsive inputs the transient damped dynamics of this system exhibit transient resonance captures (TRCs) causing high-frequency ‘bursts’ or instabilities in the response of the harvesting element. In turn, these high-frequency dynamic instabilities result in strong and sustained energy transfers from the directly excited primary system to the lightweight harvester, which, through the piezoelastic element, are harvested by the electrical component of the system or, in the present case, dissipated across a resistive element in the circuit. The primary goal of this work is to demonstrate the efficacy of employing this type of high-frequency dynamic instability to achieve enhanced nonlinear vibration energy harvesting under impulsive excitations.Journal of Sound and Vibration 07/2014; 333(14):3214–3235. DOI:10.1016/j.jsv.2014.02.017 · 1.86 Impact Factor
Conference Paper: Vibration Absorber and Harvester for Energy Efficient Structures[Show abstract] [Hide abstract]
ABSTRACT: Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternalASME 2013 International Mechanical Engineering Congress and Exposition; 11/2013
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ABSTRACT: Impedance matching techniques have been shown to extract close to the maximum theoretical power from kinetic energy harvesters. The output impedance of electromagnetic energy harvesters is frequency-dependent, which must be compensated for by the interfacing power electronics. Switched mode power converters are used to synthesise optimum, matched load impedance, controlled typically by varying duty ratio pulse width modulated gate signals. The emulated input impedance of the power converter is affected by factors such as the input and output voltage levels. In this paper, the non-synchronous boost rectifier, operated entirely in discontinuous current conduction mode, is controlled dynamically to ensure that the emulated input resistance remains at a set value under varying input and output conditions. This is achieved by employing a feed-forward control scheme that is based on calculating the time-varying optimum duty ratio as a function of the excitation frequency, the generated voltage and the converter output voltage, following the analytically derived equations. Experimental results are obtained using the proposed feed-forward control method implemented on a real-time platform. The results demonstrate the effectiveness of the presented control in terms of emulating a set resistance, and the average power that can be extracted using optimum resistance matching over a range of excitation frequencies.2013 IEEE Applied Power Electronics Conference and Exposition - APEC 2013; 03/2013