• Proceedings of the KIPE Conference
• /
• 1999.07a
• /
• pp.84-87
• /
• 1999

This paper proposes an interfaces control system to drive a ultrasonic motors(USMs). To touch surfaces and objects created within a virtua environment, the 3 DOF force-reflecting interfaces provides force feedback to users, so to feel touching real things. To effectively display the mechanical impedance of the human hand we need a device with specific characteristics, such as low inertia almost zero friction and very high stiffness. As an actuator for direct drive method, the USMs have many good advantages satisfied these conditions over conventional servo motors. To estimate capability of this interface, we did an experiment. The device works very well, as user are able to detect the edge of the wall and the stiffness of the button.

• Proceedings of the KIEE Conference
• /
• 2002.07a
• /
• pp.145-147
• /
• 2002

In this paper, the improved fault locating method using distributed parameter which calculating the reduced voltage and current according to the ground capacitance in long transmission line was proposed. For the purpose of the fault locating algorithm non influenced source impedance, the loop method was used in the system modeling analysis. To enhance the fault locating, zero sequence of the fault current which is variable according to ground capacitance was not used but positive and negative sequence. System model was simulated using EMTP software. To verify the accuracy of proposed method, in different cases 64 sampled data per cycle was used and 160km and 300km long transmission line has fault resistance $0{\Omega}\;and\;100{\Omega}$ respectively was compared.

• Proceedings of the KIEE Conference
• /
• 1999.07c
• /
• pp.1186-1188
• /
• 1999

When we perform the test related to the power distribution system such as artificial fault test, protective coordination test, distribution automation test in short length test line, Lumped Constant Circuit, a kind of variable impedance, should be attached to the test line in order to make it equivalent to a real line in length electrically. In this paper we designed the positive sequence and zero sequence Lumped Constant Circuit with optimized inductor and resister for the modification of long, 16km, distribution line, when they are attached to the short, 4km, distribution test line.

• Journal of the Korean Ceramic Society
• /
• v.32 no.1
• /
• pp.25-30
• /
• 1995

The frequenc dependence of magnetic permeability($\mu$r) and dielectric constant($\varepsilon$r) in MHz-GHz frequency range and their relationships with microwave absorbing properties were investigated in sintered and composite Ni-Zn ferrites, respectively. It was confirmed that zero reflection condition was required the real parts of permeability and permittivity in sintered specimen, and the complex permeability, permittivity and dielectric loss tangent in composite specimen. The real part of permittivity varied with the replacement of nickel by manganese in sintered Ni-Zn ferrite. Therefore, we could control the matching frequency and matching thickness.

• Proceedings of the KIEE Conference
• /
• 1992.07a
• /
• pp.138-140
• /
• 1992

This paper represents how to reduce the computer time in small signal stability analysis by selecting the dominant oscillation modes with frequency of 0.5 to 1.2 Hz using the clustering technique. Clustering technique links the buses which are expected to be similar with zero-impedance lines and the voltage variations of these buses are regarded to be identical. The computer time was reduced remarkably with this technique and the effect of clustering will be powerful in the analysis of large-scale power systems.

• ETRI Journal
• /
• v.31 no.4
• /
• pp.475-477
• /
• 2009

A balanced dual-band bandpass filter based on ${\lambda}$/2 stepped-impedance resonators and open-loop resonators is proposed in this letter. By employing a type of self-feedback structure, an extra transmission zero is introduced near the common-mode resonance frequency, and the common-mode signal is suppressed. The measured results indicate that the filter can operate in 2.46 GHz and 5.6 GHz bands, and the insertion loss is 1.85 dB and 1.9 dB, respectively. Also, better common-mode suppression is achieved.

• Journal of Institute of Control, Robotics and Systems
• /
• v.20 no.4
• /
• pp.389-394
• /
• 2014

This paper presents the effect of a reflective force computed from a first-order-hold method on the stability of a haptic system. A haptic system is composed of a haptic device with a mass and a damper, a virtual spring, a sampler and a sample-and-hold. The boundary condition of the maximum virtual stiffness is analytically derived by using the Routh-Hurwitz criterion and the condition shows that the maximum virtual stiffness is proportional to the square root of the mass and the damper of a haptic device and also is inversely proportional to the sampling time to the power of three over two. The effectiveness of the derived condition is evaluated by the simulation. When the reflective forces are computed by using the first-order-hold method, the maximum available stiffness to guarantee the stability is increased several hundred times as large as when the zero-order-hold method is applied.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.11 no.3
• /
• pp.337-344
• /
• 2000

The wavelet analysis technique is applied in the spectral domain to efficiently represent the multi-scale features of the impedance matrices. In this scheme, the 2-D quadtree decomposition (applying the wavelet transform to only the part of the matrix) method often used in image processing area is applied for a sparse moment matrix. CG(Conjugate-Gradient) method is also applied for saving memory and computation time of wavelet transformed moment matrix. Numerical examples show that for rectangular cylinder case the non-zero elements of the transformed moment matrix grows only as O($N^{1.6}$).

• Proceedings of the KIEE Conference
• /
• 1999.11b
• /
• pp.86-88
• /
• 1999

We investigated the current limiting characteristics of resistive and inductive SFCLs with $100{\Omega}$ of quench impedance for a line-to-line fault in the 154 kV transmission system. The fault simulation at the phase angles $0^{\circ}$, $45^{\circ}$, and $90^{\circ}$ showed that the resistive SFCL limited the fault current less than 15 kA without any DC component after one half cycle from the instant of the fault. On the other hand, the inductive SFCL suppressed the current below 13 kA, but with $2{\sim}3\;kA$ of DC component which decreased to zero in 6 cycles. We concluded that the inductive SFCL had higher performance in current limiting but the resistive SFCL was better from the view point of DC components.

• Progress in Superconductivity
• /
• v.1 no.1
• /
• pp.73-80
• /
• 1999

We investigated the current limiting characteristics of resistive and inductive SFCLs with 100 $\Omega$ of impedance for line-to-ground faults in the 154 kV transmission system. The fault simulation at the phase angles $0^{\circ}$, $^45{\circ}$, and $90^{\circ}$ showed that the resistive SFCL limits the fault current less than 17 kA without any DC component after one half cycle from the instant of the fault. On the other hand, the inductive SFCL suppresses the current below 14 kA, but with 5 kA of DC component which decreases to zero in 5 cycles. We concluded that the inductive SFCL has higher performance in current limiting effect, but the resistive SFCL was better from the viewpoint of less DC components.