• Journal of electromagnetic engineering and science
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• v.2 no.2
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• pp.93-99
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• 2002

The Cartesian loop chip which is one of key devices in narrow-band Walky-Talky transmitter using RZ-SSB modulation method was designed and implemented with 0.35 Um CMOS technology. The reduced size and low cost of transmitter were available by the use of direct-conversion and Cartesian loop chip, which improved the power efficiency and linearity of transmitting path. In addition, low power operation was possible through CMOS technology. The performance test results of transmitter showed -23 dBc improvement of IMD level and -30 dEc below suppression of SSB characteristic in the operation of Cartesian loop chip (closed-loop). At that time, the transmitting power was about 37 dBm (5 W). The main parameters to improve the transmitting characteristic and to compensate the distortion in feed back loop such as DC-offset, loop gain and phase value are interfaced with notebook PC to be controlled with S/W.

• The Journal of Korea Robotics Society
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• v.15 no.3
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• pp.212-220
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• 2020

This paper deals with a strategy of gain optimization for the kinematic control algorithm of a wire-driven surgical robot. The proposed controller consists of the closed-loop inverse kinematics with the back-calculation method. The closed-loop inverse kinematics has 18 PID control gains, and the back-calculation method has 6 gains. An efficient strategy is designed to optimize 18 values first and then the remaining 6 values. The optimal gain sets are searched under the step input with performance indices. In this gain optimization, the objective function is defined as the minimum value of signal-to-noise ratio of the performance indices for 6 DoF (Degree-of-Freedom) motion that is based on the Taguchi method, and the constraints are applied to obtain stable responses for each motion evenly. The gain sets obtained are verified by simulations using the test trajectories. In comparative results, the optimal gain value based on the performance index combined with ISE (integral of square error) and settling time showed the best control performance.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.12
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• pp.611-623
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• 2002

This paper introduce the real time digital simulator which is located in Korea Electric Power Research Institute. This paper also describes the methodology for the performance test of the PSS using KEPS. This test is to get a high degree of the confidence of the developed PSS before it is installed into the real power system. This has been performed in the form of closed-loop tests in which Simulator and PSS are connected and signals come and back interactively. Many tests have successfully done using KEPS which consists of 26 RTDS racks, under the large-scale power system. The simulated reduced KEPCO power system contains 88 generators and 295 buses. Through the AVR step, three phase fault and active power variation test, the effectiveness of developed PSS has been proved. This paper also presents the overview of KEPS and hardware of protype PSS.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.38-41
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• 2009

For the technology development of LOx/kerosene liquid rocket engine, turbopump-gas generator closed-loop coupled tests using 30tonf main engine components such as turbopump and gas generator except combustion chamber are performed. In the engine system operation environment, simulating combustion chamber by flow control units, the chill-down procedure, startup characteristics, nominal operability and smooth shutdown of turbopump+gas generator closed-loop coupled Test Plant are successfully confirmed. The serviceability of the turbopump and gas generator are evaluated. The feed-back control system for the turbopump rotational speed and gas generator mixture ratio are also verified. The results of closed-loop coupled test will be used as the technology development for the liquid rocket engine.

• Journal of Astronomy and Space Sciences
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• v.25 no.4
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• pp.459-470
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• 2008

DATS which is one of three subsystems of IDACS is responsible to receive Sensor Data, LRIT and HRIT in L-Band and transmit LRIT and HRIT in S-Band from/to COMS satellite. This paper shows detailed test procedures used to verify the performance and functionality of DATS after its implementation was completely finished. As a part of efforts to verify key DATS performance, G/T and EIRP were measured by using solar flux density as radio source. Regarding the verification of DATS functionality, RF loop-back test was conducted to validate if there is no BER degradation excepting MODEM/BB implementation loss occurred in the integrated DATS. Integrated with 13m antenna, DATS successfully restored image from received MTSAT-1R broadcasting data, LRIT and HRIT, of which frequencies are all L-Band. S-Band transmission was also verified through test antenna placed away from 13m antenna by measuring real LRIT and HRIT spectrum in S-Band. From those test results, DATS is determined to be fully ready to communicate with COMS in L-Band and S-Band.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.3
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• pp.11-17
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• 2003

In this paper, we implemented 2-wire (data gnd) RS232C serial communication interface by applying the Collision Sensing Multiple Access(CSMA) Protocol. The transmitting and receiving wires of RS232C pert are connected together by the interface circuit forming data wire without hardware modification On two-wired common channel connection simultaneous transmission Don mere than two hosts causes data collision. The collision is detected by loop-back test of transmission data comparing with the fed back data to detect the data distortion. Various models are adopted to reduce the probability of retransmitted data collision and experiments show the performance of each cases. Due to allowing multiple hosts to be accessed through the common communication channel with minimum circuit addition the result of this paper can be easily applied for conventional RS232C instruments and machines to connect to the single data communication line.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.794-797
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• 1988

G. Binnig and H. Rohrer introduced the Scanning Tunneling Microscope (STM) in 1982 and developed it into a powerful and not to be missed physical tool. Scanning tunneling Microscopy is a real space surface imaging method with the atomic or subatomic resolution in all three dimensions. The tip is scanned over the surface by two piezo translators mounted parallel (X-piezo and Y-piezo) to the surface and perpendicular to each other. The voltage applied to the third piezo (Z-piezo) translator mounted perpendicular to the surface to maintain the tunneling current through the gap at a constant level reflects then the topography of the surface. The feed back control loop for the constant gap current is designed using the automatic control technique. In the designing process of the feed back loop, the identification of the gap dynamics is very complex and has difficulty. In this research, using some suitable test signals, the system dynamics of the gap including the Z-piezo are investigated. Especially, in this paper, a system model is proposed for the gap and Z-piezo series system. Indicial response is used to find out the model. The driving voltage of the Z-piezo and the tunneling current are considered as input and output signals respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.9C
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• pp.871-878
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• 2002

The cartesian loop chip which is one of key devices in narrow-band Walky-Talky transmitter using RZ-SSB modulation method was designed and implemented with 0.35 ㎛ CMOS technology. The reduced size and low cost of transmitter were available by the use of direct-conversion and cartesian loop chip, which improved the power efficiency and linearity of transmitter. In addition, low power operation was possible through CMOS technology. The performance test results of transmitter showed -23㏈c improvement of IMD and -30㏈c below suppression of SSB characteristic in the operation of cartesian loop chip (closed-loop). At that time, the transmitting power was about 37㏈m (5W). The main parameters to improve the transmitting characteristic and to compensate the distortion in feed back loop such as DC-offset, loop gain and phase value are interfaced with notebook PC to be controlled with S/W.

• Journal of the Korean Geotechnical Society
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• v.28 no.12
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• pp.5-15
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• 2012

In this study, a series of CFD (Computational Fluid Dynamics) numerical analyses were performed in order to evaluate the thermal performance of six full-scale closed-loop vertical ground heat exchangers constructed in a test bed located in Wonju. The circulation HDPE pipe, borehole and surrounding ground formation were modeled using FLUENT, a finite-volume method (FVM) program, for analyzing the heat transfer process of the system. Two user-defined functions (UDFs) accounting for the difference in the temperatures of the circulating inflow and outflow fluid and the variation of the surrounding ground temperature with depth were adopted in the FLUENT model. The relevant thermal properties of materials measured in laboratory were used in the numerical analyses to compare the thermal efficiency of various types of the heat exchangers installed in the test bed. The simulation results provide a verification for the in-situ thermal response test (TRT) data. The CFD numerical back-analysis with the ground thermal conductivity of 4 W/mK yielded better agreement with the in-situ thermal response tests than with the ground thermal conductivity of 3 W/mK.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.26.3-26.3
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• 2008

This research develops a GPS-based formation-flying testbed (FFTB) for formation navigation and control. The FFTB is a simulator in which spacecraft simulation and modeling software and loop test capabilities are integrated for test and evaluation of spacecraft navigation and formation control technologies. The FFTB is composed of a GPS measurement simulation computer, flight computer, environmental computer for providing true environment data and 3D visualization computer. The testbed can be simulated with one to two spacecraft, thus enabling a variety of navigation and control algorithms to be evaluated. In a formation flying simulation, GPS measurement are generated by a GPS measurement simulator to produce pseudorange, carrier phase measurements, which are collected and exchanged by the flight processors and subsequently processed in a navigation filter to generate relative and/or absolute state estimates. These state estimates are the fed into control algorithm, which are used to generate maneuvers required to maintain the formation. In this manner, the flight processor also serves as a test platform for candidate formation control algorithm. Such maneuvers are fed back through the controller and applied to the modeled truth trajectories to close simulation loop. Currently, The FFTB has a closed-loop capability of simulating a satellite navigation solution using software based GPS measurement, we move forward to improve using SPIRENT GPS RF signal simulator and space-based GPS receiver