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Prof. Pilkee Kim
School of Mechanical Design Engineering, College of Engineering, Jeonbuk National University, 567 Baekje‑daero, Deokjin‑gu, Jeonju‑si, Jeollabuk‑do, 54896, Republic of Korea

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Research Keywords & Expertise

0 Applied Mechanics
0 Energy Harvesting
0 Nonlinear Dynamics
0 Sensors
0 Machine tool dynamics

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Journal article
Published: 10 April 2021 in Sensors
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In this study, the external load resistance of a magnetically coupled two-degree-of-freedom bistable energy harvester (2-DOF MCBEH) was optimized to maximize the harvested power output, considering the third-harmonic distortion in forced response. First, the nonlinear dynamic analysis was performed to investigate the characteristics of the large-amplitude interwell motions of the 2-DOF MCBEH. From the analysis results, it was found that the third-harmonic distortion occurs in the interwell motion of the 2-DOF MCBEH system due to the nonlinear magnetic coupling between the beams. Thus, in this study, the third-harmonic distortion was considered in the optimization process of the external load resistance of the 2-DOF MCBEH, which is different from the process of conventional impedance matching techniques suitable for linear systems. The optimal load resistances were estimated for harmonic and swept-sine excitations by using the proposed method, and all the results of the power outputs were in excellent agreements with the numerically optimized results. Furthermore, the associated power outputs were compared with the power outputs obtained by using the conventional impedance matching technique. The results of the power outputs are discussed in terms of the improvement in energy harvesting performance.

ACS Style

Jinhong Noh; Pilkee Kim; Yong-Jin Yoon. Load Resistance Optimization of a Magnetically Coupled Two-Degree-of-Freedom Bistable Energy Harvester Considering Third-Harmonic Distortion in Forced Oscillation. Sensors 2021, 21, 2668 .

AMA Style

Jinhong Noh, Pilkee Kim, Yong-Jin Yoon. Load Resistance Optimization of a Magnetically Coupled Two-Degree-of-Freedom Bistable Energy Harvester Considering Third-Harmonic Distortion in Forced Oscillation. Sensors. 2021; 21 (8):2668.

Chicago/Turabian Style

Jinhong Noh; Pilkee Kim; Yong-Jin Yoon. 2021. "Load Resistance Optimization of a Magnetically Coupled Two-Degree-of-Freedom Bistable Energy Harvester Considering Third-Harmonic Distortion in Forced Oscillation." Sensors 21, no. 8: 2668.

Journal article
Published: 06 March 2021 in Sustainability
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In this study, optimization of the external load resistance of a piezoelectric bistable energy harvester was performed for primary harmonic (period-1T) and subharmonic (period-3T) interwell motions. The analytical expression of the optimal load resistance was derived, based on the spectral analyses of the interwell motions, and evaluated. The analytical results are in excellent agreement with the numerical ones. A parametric study shows that the optimal load resistance depended on the forcing frequency, but not the intensity of the ambient vibration. Additionally, it was found that the optimal resistance for the period-3T interwell motion tended to be approximately three times larger than that for the period-1T interwell motion, which means that the optimal resistance was directly affected by the oscillation frequency (or oscillation period) of the motion rather than the forcing frequency. For broadband energy harvesting applications, the subharmonic interwell motion is also useful, in addition to the primary harmonic interwell motion. In designing such piezoelectric bistable energy harvesters, the frequency dependency of the optimal load resistance should be considered properly depending on ambient vibrations.

ACS Style

Sungryong Bae; Pilkee Kim. Load Resistance Optimization of a Broadband Bistable Piezoelectric Energy Harvester for Primary Harmonic and Subharmonic Behaviors. Sustainability 2021, 13, 2865 .

AMA Style

Sungryong Bae, Pilkee Kim. Load Resistance Optimization of a Broadband Bistable Piezoelectric Energy Harvester for Primary Harmonic and Subharmonic Behaviors. Sustainability. 2021; 13 (5):2865.

Chicago/Turabian Style

Sungryong Bae; Pilkee Kim. 2021. "Load Resistance Optimization of a Broadband Bistable Piezoelectric Energy Harvester for Primary Harmonic and Subharmonic Behaviors." Sustainability 13, no. 5: 2865.

Journal article
Published: 22 February 2021 in Sensors
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In this study, a semi-analytic approach to optimizing the external load resistance of a bi-stable electromagnetic energy harvester is presented based on the harmonic balance method. The harmonic balance analyses for the primary harmonic (period-1T) and two subharmonic (period-3T and 5T) interwell motions of the energy harvester are performed with the Fourier series solutions of the individual motions determined by spectral analyses. For each motion, an optimization problem for maximizing the output power of the energy harvester is formulated based on the harmonic balance solutions and then solved to estimate the optimal external load resistance. The results of a parametric study show that the optimal load resistance significantly depends on the inductive reactance and internal resistance of a solenoid coil––the higher the oscillation frequency of an interwell motion (or the larger the inductance of the coil) is, the larger the optimal load resistance. In particular, when the frequency of the ambient vibration source is relatively high, the non-linear dynamic characteristics of an interwell motion should be considered in the optimization process of the electromagnetic energy harvester. Compared with conventional resistance-matching techniques, the proposed semi-analytic approach could provide a more accurate estimation of the external load resistance.

ACS Style

Sungryong Bae; Pilkee Kim. Load Resistance Optimization of Bi-Stable Electromagnetic Energy Harvester Based on Harmonic Balance. Sensors 2021, 21, 1505 .

AMA Style

Sungryong Bae, Pilkee Kim. Load Resistance Optimization of Bi-Stable Electromagnetic Energy Harvester Based on Harmonic Balance. Sensors. 2021; 21 (4):1505.

Chicago/Turabian Style

Sungryong Bae; Pilkee Kim. 2021. "Load Resistance Optimization of Bi-Stable Electromagnetic Energy Harvester Based on Harmonic Balance." Sensors 21, no. 4: 1505.

Regular paper
Published: 28 March 2019 in International Journal of Precision Engineering and Manufacturing-Green Technology
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This study investigates possible routes to high-energy orbit motion (HEOM) from which high electrical power can be generated in a magnetically coupled bistable energy harvester (MCBEH) with two degrees of freedom (DOFs). By examining the frequency responses of the 2-DOF MCBEH, four main routes to HEOM are found to originate from two primary and two secondary intrawell resonances. For conventional BEHs (CBEHs), only primary resonance has been considered important in the design process, because secondary resonances can hardly initiate HEOM. However, for the 2-DOF MCBEH, it is observed that the secondary resonances also form the separate frequency bands of the HEOM for energy harvesting. Furthermore, with the increase of the excitation intensity, the secondary resonances tend to bridge the gap between the frequency bands for the two primary resonances, significantly enhancing the operating frequency bandwidth (up to 200% with respect to the CBEH used in this study). The enhanced broadband performance of the 2-DOF MCBEH is theoretically and experimentally evaluated and discussed in comparison with the CBEH.

ACS Style

Minh Sang Nguyen; Yong-Jin Yoon; Pilkee Kim. Enhanced Broadband Performance of Magnetically Coupled 2-DOF Bistable Energy Harvester with Secondary Intrawell Resonances. International Journal of Precision Engineering and Manufacturing-Green Technology 2019, 6, 521 -530.

AMA Style

Minh Sang Nguyen, Yong-Jin Yoon, Pilkee Kim. Enhanced Broadband Performance of Magnetically Coupled 2-DOF Bistable Energy Harvester with Secondary Intrawell Resonances. International Journal of Precision Engineering and Manufacturing-Green Technology. 2019; 6 (3):521-530.

Chicago/Turabian Style

Minh Sang Nguyen; Yong-Jin Yoon; Pilkee Kim. 2019. "Enhanced Broadband Performance of Magnetically Coupled 2-DOF Bistable Energy Harvester with Secondary Intrawell Resonances." International Journal of Precision Engineering and Manufacturing-Green Technology 6, no. 3: 521-530.

Journal article
Published: 18 December 2017 in Applied Physics Letters
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In this study, we propose a bistable energy harvester with an auxiliary magnet oscillator (BEH-O), whose motion is mechanically rectified to enhance its broadband energy harvesting performance. The design of the proposed BEH-O system is based on local modification of the double-well potential. The auxiliary oscillator with the mechanical rectifier is designed in such a manner that its rectified half-sine motion tends to reduce the saddle barrier of restoring potential, leading to a possibility of an easier escape from the potential well, while keeping other parts of the potential, thereby maintaining high-energy orbital motion. Consequently, the lower bound of the operating frequency band of the BEH-O is reduced, when compared to its conventional counterpart, i.e., conventional bistable energy harvester (CBEH), while its upper bound remains unchanged. Such a broader frequency band of the BEH-O can be directly compared with that of the CBEH, as there is little difference in the high-energy orbital motion between the two. This beneficial effect of the BEH-O system is theoretically and experimentally supported by bifurcation analyses and frequency response analyses.

ACS Style

Minh Sang Nguyen; Yong-Jin Yoon; Ojin Kwon; Pilkee Kim. Lowering the potential barrier of a bistable energy harvester with mechanically rectified motion of an auxiliary magnet oscillator. Applied Physics Letters 2017, 111, 253905 .

AMA Style

Minh Sang Nguyen, Yong-Jin Yoon, Ojin Kwon, Pilkee Kim. Lowering the potential barrier of a bistable energy harvester with mechanically rectified motion of an auxiliary magnet oscillator. Applied Physics Letters. 2017; 111 (25):253905.

Chicago/Turabian Style

Minh Sang Nguyen; Yong-Jin Yoon; Ojin Kwon; Pilkee Kim. 2017. "Lowering the potential barrier of a bistable energy harvester with mechanically rectified motion of an auxiliary magnet oscillator." Applied Physics Letters 111, no. 25: 253905.