• Smart Structures and Systems
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• v.25 no.4
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• pp.393-399
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• 2020

In this paper, the design method and experimental validation for the two-degree-of-freedom (2DOF) electromagnetic energy harvester are presented. The harvester consists of the rigid body suspended by four tension springs and electromagnetic transducers. Once the two resonant frequencies and the mass properties are specified, both the constant and the positions for the springs can be determined in the closed form. The designed harvester can locate two resonant peaks close to each other and forms the extended frequency bandwidth for power harvesting. Halbach magnet array is also introduced to enhance the output power. In the experiment, two resonant frequencies are measured at 34.9 and 37.6 Hz and the frequency bandwidth improves to 5 Hz at the voltage level of 207.9 mV. The normalized peak power of 4.587 mW/G² is obtained at the optimal load resistor of 367 Ω.

• Journal of the Korean Society of Safety
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• v.3 no.1
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• pp.21-29
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• 1988

Conventional pwm switching power supply have the disadvantage some aspects of size, light weight, noise and system stability. High frequency Series Resonant Converter (SRC), described in this paper, almost improve above disadvantages. We use the state plane technique as analysis method. This technique is powerful tool which can clearly analyze the peak stress of the state variables inside the converter, Here, we can define each operation mode from frequency ratio Fsn, switching frequency to resonant frequency, and we analyze the output performance in each operation mode. To verify the theoretical analysis, we compose the actual converter, and the experimental results are compared with analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.459-468
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• 2014

An additional relationship equation is numerically obtained to increase the accuracy of the conventional equation for obtaining the resonant frequency of a resonator. Although the conventional equation is widely used in industry because of its simplicity, it does not provide enough information on the cavity or the neck of the resonator for noise reduction in a duct. Resonator designers have difficulty implementing resonator design owing to the uncertainty in geometry presented by the well-known formula for determining the resonant frequency. To overcome this problem, this work determines an approximate equation using results of numerical calculation. To this end, shape parameters of the neck and cavity of a resonator are defined, and an equation describing the relationship between them is derived by adjusting the peak frequency in the transmission loss curve of a resonator to its resonant frequency. The application and validity of the derived equation are investigated in a numerical simulation and an acoustic experiment, respectively.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.107-111
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• 2013

The gyroscopes have been used as a suitable inertial instrument for the navigation guidance and attitude controls. The accuracy as very sensitive sensor is limited by the lock-in region (dead band) due to the frequency coupling between two counter-propagating waves at low rotation rates. This frequency coupling gives no phase difference, and an angular increment is not detected. This problem can be overcome by mechanically dithering the gyroscope. This paper presents the design method of mechanical dither by the theoretical considerations and the verification of the theoretical equations through FEM applications. As a result, comparing to the past result, the maximum prediction error of resonant frequency was within 3 percent and peak dither rate was within 5 percent. It was found that the theoretical equations can be feasible for the mechanical performance of dither.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.6
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• pp.1949-1954
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• 2010

The gyroscopes have been used as a suitable inertial instrument for the navigation guidance and attitude controls. The accuracy as very sensitive sensor is limited by the lock-in region(dead band) due to the frequency coupling between two counter-propagating waves at low rotation rates. This frequency coupling gives no phase difference, and an angular increment is not detected. This problem can be overcome by mechanically dithering the gyroscope. This paper presents the design method of mechanical dither by the theoretical considerations and the verification of the theoretical equations through FEM(Finite Element Method) applications. As a result, the maximum prediction error of resonant frequency and peak dither rate was under 5 percent. The theoretical equations for the mechanical performances of dither can be said to be feasible.

• Journal of Power Electronics
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• v.11 no.4
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• pp.599-605
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• 2011

This paper proposes a gain scheduling method that improves the stability of grid-connected systems employing an LCL-filter. The method adjusts the current controller gain through an estimation of the grid impedance in order to reduce the resonance that occurs when using an LCL-filter to reduce switching harmonics. An LCL-filter typically has a frequency spectrum with a resonance peak. A change of the grid-impedance results in a change to the resonant frequency. Therefore an LCL-filter needs a damping method that is applicable when changing the grid impedance for stable system control. The proposed method instantaneously estimates the grid impedance and observes the resonant frequency at the same time. Consequently, the proposed method adjusts the current controller gain using a gain scheduling method in order to guarantee current controller stability when a change in the resonant frequency occurs. The effectiveness of the proposed method has been verified by simulations and experimental results.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.6
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• pp.916-926
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• 1994

A high frequency and soft-switched AC-to-DC rectifier employing a series-type resonant circuit is proposed to overcome the disadvantages of the conventional peak-rectifying circuit. Using the proposed rectifier, the high power factor and low harmonic currents are obtained in the AC line. Furthermore, several advantages such as the high power density and wide output voltage range can be available. Through the simulation and experimental results, the usefulness of the proposed rectifier is verified.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.2
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• pp.114-121
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• 2016

This paper is Instant space vector PWM(Pulse Width Modulation)power conversion devices in switching power semiconductors from my generation to losses and switching when the voltage surge and current surge of electronic noise(EMI: Electro Magnetic Interference / RFI: Radio Frequency Interference)to effectively minimize the power soft-switching power conversion circuit topologies of auxiliary resonant DC tank for the purpose of high performance realization of the electric power conversion system by the high-speed switching of a semiconductor device(AQRDCT simultaneously : an active auxiliary resonance using auxiliary Quasi-resonant DC tank)DC link snubber switch has adopted a three-phase voltage inverter. AQRDCL proposed in this paper can reduce the effective and current peak stress of the power semiconductors of the auxiliary resonant snubber circuit compared to the conventional active-resonant DC link snubber, it is not necessary to install the clamp switch of the auxiliary resonant DC link, DC the peak current and power loss of the bus line can be reduced.

• Journal of Advanced Navigation Technology
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• v.25 no.1
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• pp.90-95
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• 2021

In this paper, the design method for a high-sensitivity compact resonator for chipless RFID tags is proposed. Proposed high-sensitivity compact resonator uses an interdigital-capacitor structure instead of a capacitor-shaped strip structure in a conventional ELC resonator. The length of the electrode plate of the IDC structure is longer than that of the conventional capacitor-shaped structure, resulting in a larger equivalent capacitance of the resonator. This can lower the resonant peak frequency of the RCS characteristic. Two resonators with the same length of the square loop and the width of the strip are fabricated on an RF-301 substrate with a thickness of 0.8 mm. The experiment results show that the resonant peak frequency and value of the bistatic RCS for the ELC resonator were 4.305 GHz and -30.39 dBsm, whereas those of the proposed IDC resonator were 3.295 GHz and -36.91 dBsm. Therefore, the size of the resonator is reduced by 23.5% based on the measured resonant peak frequency of the RCS characteristic.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.261-261
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• 2007

Wearable and ubiquitous micro systems will be greatly growing and their related devices should be self-powered in order to avoid the replacement of finite power sources, for example, by scavenging energy from the environment. With ever reducing power requirements of both analog and digital circuits, power scavenging approaches are becoming increasingly realistic. One approach is to drive an electromechanical converter from ambient motion or vibration. Vibration-driven generators based on electromagnetic, electrostatic and piezoelectric technologies have been demonstrated. Among various generator types proposed so far, piezoelectric generator possesses considerable potential in micro system. To overcome low mechanical-to- electric energy conversion, the piezoelectric device should activate in resonance mode in response to external vibration. Normally, the external vibration excretes at low frequency ranging 0.1 to 200 Hz, whereas the resonant frequencies of the devices are fixed as constant. Therefore, keeping their resonant mode in varying external vibration can be one of important points in enhancing the conversion efficiency. We investigated the possibility of use of multi-bender type piezoelectric devices. To match the external vibration frequency with the device resonant frequency, the various devices with different resonant frequency were chosen. Under an external vibration acceleration of 0.1G at 120 Hz, the device exhibited a peak-to-peak voltage of 2.8 V and a power of 0.5 mw in resonance mode.