• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.213-216
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• 2003

Recently a new high power device GCT (Gate Commutated Turn-off) thyristor has been successfully introduced to high power converting application areas. GCT thyristor has a quite different turn-off mechanism to the GTO thyristor. All main current during turn-off operation is commutated to the gate. Therefore, IGCT thyristor has many superior characteristics compared with GTO thyristor; especially, snubberless tum-off capacibility and higher turn-on capacibility. The basic structure of the GeT thyristor is same as that of the GTO thyristor. This makes the blocking voltage higher and controllable on-state current higher. The turn-off characteristic of the GCT thyristor is influenced by the minority carrier lifetime and the performance of the gate drive unit. In this paper, we present turn-off characteristics of the 2.5kV PT(Punch-Through) type GCT as a function of the minority carrier lifetime and variation of the doping profile shape of p-base region.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.235-240
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• 2002

This paper shows the desist concept of an ATS(Antenna Tracking Software) to control the movement of the MSC(Multi-Spectral Camera) antenna. The MSC has a two-axes directional X-band antenna for image transmission to KGS(KOMSAT2 Ground Station). The main objective of the ATS is to drive the APM(Antenna Pointing Mechanism) to the required elevation and the azimuth position according to an appropriate TPF(Tracking Parameter File). The ATS is implemented as one task of the SBC(Single Board Computer) software, which uses VxWorks as a real time OS. The ATS has several operational modes such as STANDBY mode, First EL mode, First AZ mode, Normal Operation mode, and so on. The ATS uses two PI controllers fur the velocity and the position loop respectively, to satisfy the requirements specification. In order to show the feasibility of the described design concept, the various simulations and the experiments are performed under specific test configuration.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.563-566
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• 2003

We have designed the power control unit which belongs to the power cabinet and controls the power supplied to Control Rod Drive Mechanism(CRDM) as a digital system based on Digital Signal Processor(DSP). The power control unit dualized as the form of Master/Slave has had its increased reality. The Central Process Unit(CPU) board of a power control unit possesses two Digital Signal Processors(DSPs) of the control DSP for performing the tasks of power control and system monitoring and the communication of the Control DSP and the Communication DSP. To accomplish the functions requested in the power control unit effectively, we have installed Field Programmable Gate Arrays(FPGAS) on the CPU board and have FPGAs perform the memory mapping, the generation of each chip selection signal, the giving and receiving of the signals between the power controllers dualized, the fault detection and the generation of the firing signals.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.7
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• pp.730-736
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• 2012

Latest, many researchers do research on wearable robot. The purpose of the researches is very diverse, it will improve efficiency in the industry, taken to replace the many workers in the military field and taken to assist bodily functions run out by aging. However, there is no clear Differentiated strategy depending on the purpose for design and control of the wearable robot. Although a common purpose is to drive the robot by the sensor signal (intent signals), the optimization about the mechanism and control studies must be done according to the user's physical ability and purpose. In this study, the study's first phase for the development of wearable robotic gait rehabilitation, gait characteristics were analyzed elders and hemiplegia patients using a 3D gait analysis system (VICON512). As a result, asymmetric gait characteristics of the hemiplegia patients were found compared with the normal elderly.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.237-243
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• 1996

Current low head and small scale hydroturbines have limitations in the minimum required head and flow rate for efficient operation. This study attempts to develop a new concept hydroturbine which is expected to run efficiently even in very low head and small flow rate, so that the limitations on the conventional small scale hydropower could be alleviated and competition with other alternative energy sources in the economic respect could be attained. A small scale catapillar track- hydroturbine was fabricated and the performance test was carried out in a water tunnel over the head range of H = 0.8 m ~ 1.26 m. The peak turbine efficiency was 41.3% at the speed ratio of 0.6, and the turbine loss was mostly due to the friction at the chain drive used for power transmission from the runner to the shafts. This type of turbine is expected to become competitive when some improvement in the power transmission mechanism is made.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.318-323
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• 2005

This paper introduces the mechanism of the ESD (Electrostatic discharge) in the HDD spindle system using FDBs (Fluid Dynamic Bearings). When a HDD (Hard Disk Drive) spindle system is rotating, triboelectric charging occurs in the FDBs through the friction of the lubricant between the rotating shaft and stationary sleeve. And this electrostatic charge is accumulated in the rotating part of the HDD spindle system because it is insulated from the ground by the lubricant. This research shows experimentally that the behavior of electric charge and discharge in the FDB spindle system is the same as that of a capacitor. It also measures the electrostatic charge and discharge of the FDB spindle system due to the chanse of humidity, supporting load and motor speed. This research shows that the control of ESD is required in the HDD spindle system using FDBs, because the electrostatic charge accumulated in the FDB spindle system may cause the breakdown damage of the GMR head and data loss consequently.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.7
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• pp.658-664
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• 2010

A control element drive mechanism(CEDM) is a reactor regulating system, which inserts, withdraws or maintains a control rod containing a neutron absorbing material within a reactor core to control the reactivity of the core. The ball-screw type CEDM for the integral reactor has a spring-damper system to reduce the impact force due to the scram of the CEDM. This paper describes the experimental results to obtain the drop and damping characteristics of the CEDM. The drop tests are performed by using a drop test rig and a facility. A drop time and a displacement after an impact are measured using a LVDT. The influences of the rod weight, the drop height and the flow area of hydraulic damper on the drop and damping behavior are also estimated on the basis of test results. The drop time of the control element is within 4.5s to meet the design requirement, and the maximum displacement is measured as 15.6 mm. It is also found that the damping system using a spring-hydraulic damper plays a good damper role in the CEDM.

• Journal of Drive and Control
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• v.12 no.3
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• pp.11-17
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• 2015

An intelligent deburring control (IDC) device is used to control the constant force for a deburring tool mounted on the end-effector of a robotic arm. This device maintains a constant contact force between the deburring tool and the workpiece in order to provide a good deburring performance. In this paper, we build a mathematical model in Matlab/Simulink to estimate the force control mechanism of the pneumatic system for the IDC device. The Simulink blocks are built for each separate part and are linked into an integrated simulation system. Such a model also relies on the effects of the flow rate through the valve, air compressibility in the cylinder, and time delay in the pressure valve. The results of the simulation are compared to a simple experiment in which convenient math modeling is performed. These results are then used to optimize the mechanical design and to develop a force control algorithm for the pneumatic cylinder.

• Journal of Drive and Control
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• v.11 no.3
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• pp.47-54
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• 2014

Clutches are an integral part of the automatic transmission for changing gears. Modern automatic transmissions make extensive use of wet multiple-disc clutches employing hydraulic actuation mechanism with electronic control. Although nowadays, highly advanced shifting algorithm implements the superior shift quality and transmission efficiency, its performance should be based on smooth, reliable engagement with a reasonably durable friction material as well as stable clutch piston dynamics. Particularly, clutch filling control is the crucial part of shifting process because only the open-loop control is available due to the lack of measurement. In this paper, the effect of clutch-fill control parameters on clutch piston dynamics is experimentally investigated by using clutch piston test equipment which enables the clutch piston to actuate similar to real shifting conditions. The experimental analysis results can be expected to be utilized for the calibration of proportional solenoid valve as reference current profile data in vehicle test.

• Journal of Drive and Control
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• v.11 no.3
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• pp.31-40
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• 2014

This paper proposes a multi absorbing wave energy converter design, in which a hydrostatic transmission is used to transfer wave energy to electric energy. The most important feature of this system is its combination of the pressure coupling principle with the use of a hydraulic accumulator to eliminate the effects of wave power fluctuation; this maintains a constant speed of the hydraulic motor. Tilt motion of a floating buoy was employed as the power take-off mechanism. Furthermore, a PID controller was designed to carry out the speed control of the hydraulic motor. The design offers some advantages such as extending the life of the hydraulic components, increasing the amount of energy harvested, and stabilizing the output speed.