• Proceedings of the KWS Conference
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• 2005.06a
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• pp.94-96
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• 2005

Welding process of ultra thin stainless steel foil was investigated using a single mode Yb-fiber laser with a CW maximum output power 40W. In micro welding, critical power density for keyhole welding was 1 to 2 orders larger higher than in macro-welding due to larger thermal conduction, extremely high speed welding becomes possible.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.137-143
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• 2013

This paper presents development of variable speed generation (VSG) system with energy saving function. The rubber tyred gantry crane (RTGC) requires the power from diesel-engine. Significant fuel savings by reducing the engine speed can be achieved, because all of operation modes except hoisting are required lower power than rated value of engine. When low speed operation output voltage of generator is decrease until acceptable range of motor driver inverters and auxiliary load supplier. According to power demand engine speed is varying from 20 to 60Hz, and voltage is varying between 210Vac and 480Vac. When idle mode or low power operation dc/dc converter operates by constant output voltage control and inverters dc site voltage is compensated by it. This paper proposed 3-phase interleaved boost converter which has the same structure as the commercially available 3-phase inverter and current sharing capability. 400kW interleaved converter is designed and a performance of converter is evaluated through several experiments with a RTGC system. Energy saving VSG system can cut down fuel consumption by 36% and 21.3% at idle and unidirectional load operations.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.1
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• pp.18-23
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• 2006

Cutting by a high speed laser cutting machine is one of most effective technologies to improve productivity. This paper has presented the cutting characteristics and optimal cutting conditions in a high speed feeding type laser cutting machine by using Tacuchi method in the design of experiment. An L9(34) orthogonal array is adopted to study the effect of adjustment parameters. The adjustment parameters consist of cutting speed, laser power, laser output duty and assistant gas pressure. The surface roughness of sheet metal is regarded as a quality feature. Analysis of variance is performed in order to evaluate the effect of adjustment parameters on the quality feature of laser cutting process.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1182-1188
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• 2011

By storing various train information in running high speed train, we can analyze the cause of train accident efficiently. we have developed the smart and high available control method to control and manage the hardware modules. The hardware modules for event recorder consist CPU, Digital Input and Output, Pulse Input, Communication, Control Panel and Crash Protected Memory. The real time operation system is used to totally control and manage the various hardware modules. The main function of control method is collection of train information, calculation of train speed, interface with other on-board control system, storing and retrieving train information, and communication with Control Panel. In Control Panel, it displays the current train speed and the status of event recorder effectively. Also user interface is provided in Control Panel.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.657-658
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• 2006

A Novel level-shifter circuit for Display Panel Driver is presented. A Proposed level-shifter is for the high speed and high-voltage driving capability. In order to achieve this purpose, the proposed level-shifter restricts and separates the Vgs of the output driver's pull-up PMOS and pull-down NMOS with Zener diode. And a speed-up PMOS transistor is introduced to reduce delay. The control signal of speed-up PMOS was designed by bootstrapping method to minimize the gate to source (Vgs) voltage to avoid Vgs breakdown.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.6
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• pp.77-83
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• 2004

Cutting by a high speed laser cutting machine is one of most effective technologies to improve productivity. This paper has studied to obtain the cutting characteristics and optimal cutting conditions in a high speed feeding type laser cutting machine by Tacuchi method in design of experiments. A Lf(34) orthogonal array is adopted to study the effect of adjustment parameter. The adjustment parameters consist of cutting speed, laser power, laser output duty and assistant gas pressure. And the quality feature is selected as surface roughness of sheet metal. Variance analysis is performed in order to evaluate the effect of adjustment parameters on the quality feature of laser cutting process.

• Journal of Sensor Science and Technology
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• v.30 no.2
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• pp.82-87
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• 2021

In this paper, we propose a high-speed, low-power complementary metal-oxide semiconductor (CMOS) binary image sensor featuring a gate/body-tied (GBT) p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET)-type photodetector based on a double-tail comparator. The GBT photodetector forms a structure in which the floating gate (n+ polysilicon) and body of the PMOSFET are tied, and amplifies the photocurrent generated by incident light. The double-tail comparator compares the output signal of a pixel against a reference voltage and returns a binary signal, and it exhibits improved power consumption and processing speed compared with those of a conventional two-stage comparator. The proposed sensor has the advantages of a high signal processing speed and low power consumption. The proposed CMOS binary image sensor was designed and fabricated using a standard 0.18 ㎛ CMOS process.

• International journal of advanced smart convergence
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• v.12 no.4
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• pp.26-34
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• 2023

A high-speed data transmission system is designed for the ground inspection equipment of satellite measurement and control. Based on USB2.0, the system consists of interface chip CY7C68013A, programmable logic processing unit EP4CE30F23C8, analog/digital and digital/analog conversion units. The working principle of data transmission is analyzed, and the system software logic and hardware composition scheme are detailed. The system was utilized to output/capture and store specific data packets. The results show that the high-speed data transmission speed can reach 38MB/s, and the system is effective for satellite test requirements.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.2
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• pp.189-195
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• 2005

This paper presents a new velocity estimation strategy for a non-salient permanent magnet synchronous motor drive without high frequency signal injection or special PWM pattern. This approach is based on the d-axis current regulator output voltage of the drive system, which contains the rotor position error information. The rotor velocity can be estimated through a rotor position tracking PI controller that controls the position error at zero. For zero and low speed operation, the PI gain of the rotor position tracking controller has a variable structure according to the estimated rotor velocity. Then, at zero speed, the rotor position and velocity have sluggish dynamics because the varying gains are very low in this region. In order to boost the bandwidth of the PI controller during zero speed, the loop recovery technique is applied to the control system. The PI tuning formulas are also derived by analyzing this control system by frequency domain specifications such as phase margin and bandwidth assignment.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.63-64
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• 2017

This paper proposes a speed estimator for sensorless control of diesel-generator (genset) systems, where the speed of the genset is calculated from the back-EMF frequency of the generator. The back-EMF frequency is extracted from a phase output current by using multiple second-order generalized integrators (SOGIs) connected in parallel and series and separated frequency-locked loops. The proposed method (PS-SOGI-FLL) is able to estimate the fundamental frequency in the distorted output current with high accuracy and strong robustness. Simulation results are shown to verify the validity of the proposed method.