• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.11 no.5
• /
• pp.97-102
• /
• 2012

In this paper, each electrical length and harmonics of the multi-stage SIR are calculated by using the input impedance for the variable application of SIR in the microwave systems. The size reduced ratio of the SIR is slightly reduced as increasing of the number of stage. The impedance ratio between lower and higher impedance of the SIR has the dominant effect on the size reduced ratio and harmonic characteristics. Also the equivalent impedance of the SIR is a geometric mean between lower and higher impedance and the quality factor of the SIR is similar to the half-wavelength resonator's.

• Proceedings of the KIEE Conference
• /
• 2002.07d
• /
• pp.2699-2701
• /
• 2002

In this study, a system for measurement of impedance (transmission parameter) on the human muscle was constructed. The system composed of the stimulating part for input with milli-voltage and the measuring part for measurement of transmission voltage in human muscle. As a result of this experiment, the frequency characteristic of each subject represent that the transmission voltage goes up in spite of a constant input voltage according to frequency (1Hz -50kHz) increment. Namely, the amplitude of input signal was not reflected but frequency was reflected on the measured results. This result be estimated that the proposed system is able to measure passive electrical characteristic of human body.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.51 no.10
• /
• pp.581-586
• /
• 2002

To improve the current waveform of diode rectifiers, we propose a new operating principle for the voltage-doubler diode rectifiers. In the conventional voltage-doubler rectifier circuit, relatively large capacitors are used to boost the output voltage, while the proposed circuit uses smaller ones and a small reactor not to boost the output voltage but improve the input current waveform. A circuit design method is shown by experimentation and confirmed simulation. The experimental results of the proposed diode rectifier satisfies the harmonic guide lines. A high input power factor of 97(%) and an efficiency of 98[%] are also obtained. The new rectifier with no controlled switches meet the harmonic guide lines, resulting in a simple, reliable and low-cost at-to dc converters in comparison with the boost-type current-improving circuits. This paper proposes a nonlinear impedance circuit composed by diodes and inductors or capacitors. This circuit needs no control circuits and switches, and the impedance value is changed by the polarity of current or voltage. And this paper presents one of these applications to improve the input current of capacitor input diode rectifiers. The rectifier using the nonlinear impedance circuit is constructed with four diodes and four capacitors in addition to the conventional rectifiers, that is, it has eight diodes and five capacitors, including a DC link capacitor. It makes harmonic components of the input current reduction and the power factor improvement. Half pulse-width modulated (HPWM) inverter was explained compared with conventional pulse width modulated(PWM) inverter. Proposed HPWM inverter eliminated dead-time by lowering switching loss and holding over-shooting.

• Proceedings of the IEEK Conference
• /
• 2004.06b
• /
• pp.477-480
• /
• 2004

We studied the characteristics of impedance and electromechanical coupling coefficient in ZnO and AIN thin films by using resonance frequency spectrum method. The response peak of impedance decreased with the decrease of thickness of piezoelectrics, the number of mode of response peak increased with the increase of substrate thickness. An error of $k_{t}^{2}$ estimated from input $k_{t}^{2}$ increased as the thickness of piezoelectrics decreased and the thickness of substrate increased. Also, the error was increased in case of a large acoustic impedance of substrate. It was found that the composite resonator operating in optimized condition could be designed through the resonance frequency spectrum analysis of composited resonator consisted of piezoelectric thin film and substrate.

• The Journal of Korea Robotics Society
• /
• v.16 no.1
• /
• pp.72-78
• /
• 2021

This paper presents a robust impedance control of high-DOF robot based on disturbance observer(DOB). A novel DOB is derived by considering the residual disturbance caused by the difference between actual disturbance and disturbance decoupling input which utilizes the estimated disturbance. It focuses on the elimination of the residual disturbance and improvement of the control performance as well as the good estimation of disturbances. In the control of high-DOF robot, numerical dynamic model, which is conducted by a software based on dynamics, is utilized because the analytical model of high-DOF robot is difficult to be obtained. The simulation of high-DOF robot with numerical dynamic model is provided to verify the performance of the proposed controller.

• Journal of electromagnetic engineering and science
• /
• v.2 no.1
• /
• pp.45-49
• /
• 2002

This paper presents the basic characteristics of a forced resonant type EMI dipole antennas for frequencies below 80 MHz in which two reactance elements are used for the impedance matching at the fined point. The input impedance of the short dipole less than half-wavelength is controlled by the properly determined loading position and the value of loading reactance. The numerical results show that the small-sized EMI dipole antenna with loller antenna factors for frequencies below 80 MHz can be realized by the reactance loading. In case tole proposed center driven forced resonant type EMI dipole antenna with 0.3 λ length is loaded from the center, the input impedance is matched at feed line with 50 $\Omega$, and hence the antenna has lower factors in the frequency range of 30 to 80 MHz.

• Journal of Magnetics
• /
• v.18 no.4
• /
• pp.428-431
• /
• 2013

We demonstrate that a partial loading of $Ni_{0.5}Zn_{0.5}Fe_2O_4$ (Ni-Zn ferrite) film remarkably improves impedance matching of electrically small $Ba_3Co_2Fe_{24}O_{41}$ ($Co_2Z$) hexaferrite antenna. A 3 ${\mu}m$ thick Ni-Zn ferrite film was deposited on a silicon wafer by the electrophoresis deposition process and post-annealed at $400^{\circ}C$. The fabricated Ni-Zn ferrite film has saturation magnetization of $268emu/cm^3$ and coercivity of 89 Oe. A partial loading of the Ni-Zn ferrite film on the $Co_2Z$ hexaferrite helical antenna increases antenna return loss to 24.7 dB from 9.0 dB of the $Co_2Z$ antenna. Experimental results show that impedance matching and maximum input power transmission to the antenna without additional matching elements can be realized, while keeping almost the same size as the $Co_2Z$ antenna size.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.3
• /
• pp.643-650
• /
• 2017

The control of flexible joint robot is getting more attentions because its applications are more frequently used for robot systems in these days. This paper proposes a robust impedance controller for the flexible joint robot by using integral sliding mode control and backstepping control. The sliding mode control decouple disturbances completely but requires matching condition for disturbances. The dynamic model of flexible joint robot is divided into motor side and link side and the disturbance of the link side does not satisfy matching condition and cannot be decoupled directly by the actual input in the motor side. To overcome this difficulty, backstepping control technique is used with sliding mode control. The mismatched disturbance in the link side is changed into matched one in the respect to virtual control input which is the state controlled by actual input in the motor side. Integral sliding mode control is used to preserve the impedance control performance and the improved robustness at the same time.

• Journal of KSNVE
• /
• v.11 no.2
• /
• pp.257-264
• /
• 2001

In this research, piezoelectric smart structures are applied for SEA(Statistical Energy Analysis), which is well known approach for high frequency analysis. A new input power measurement based on piezoelectric electrical power measurement is proposed and compared with the conventional method in SEA. As an example, a simple aluminum beam on which piezoelectric actuator is attached is considered. By measuring the electrical impedance and electrical current of the piezoelectric actuator, the electrical power given on the actuator is found and this is In turn converted into the mechanical energy. From the measured value of the stored energy of the beam, the Internal loss factor is calculated and this value shows a good agreement with that given by the conventional method as well as the theoretical value. To compare the coupling loss factor, L-shape beam system which consists of a aluminum beam subsystem and a steel beam subsystem coupled by three pin is taken as second example. The input power and stored energy of each subsystem are found by the proposed approach. The coupling loss factor found by the electrical input power obtained from the piezoelectric actuator exhibits similar trend to the value found by the conventional method as well as the theoretical value. In conclusion, the use of SEA for high frequency application of piezoelectric smart structures is Possible. Especially, the input power that is essential for SEA can be found accurately by measuring the electrical input power of the piezoelectric actuator.

• Korean Journal of Optics and Photonics
• /
• v.19 no.1
• /
• pp.9-14
• /
• 2008

In this paper, a new type of Yagi-Uda antenna that operates in the terahertz frequencies is designed. The proposed Yagi-Uda antenna can obtain high input resistance of approximately $2000{\Omega}$ at the resonance frequency by using a full-wavelength dipole instead of a half-wavelength dipole as the driver element. The current leakage into the bias line was minimized by applying the photonic bandgap structure to the bias line. By designing the antenna on a thin substrate, the impedance lowering of an antenna caused by the relative dielectric constant of the substrate was prevented and the end-fire radiation pattern which is the original radiation characteristic of the Yagi-Uda antenna could be obtained. We expect that the proposed Yagi-Uda antenna can achieve increased terahertz output power by improving the impedance mismatching problem with the photomixer.