• Journal of Advanced Marine Engineering and Technology
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• v.32 no.8
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• pp.1303-1308
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• 2008

Keeping cooling water temperature higher within the allowable range helps marine engines to run in more efficient condition especially when the engine load is low. Temperature control of jacket cooling water in outlet side of main engine has been more widely adopted to ships these days for the purpose to reduce fuel consumption rate. But If the temperature sensor for the control loop is placed at the outlet of engine, it brings more difficulties in attaining stable and desirable properties due to dead times included in pipe length and engine itself comparing to the case where the measuring point is at the inlet side of main engine. In relation with this problem, Feed-forward control could be one of realistic solutions as it reveals good properties and requires less cost for system configuration. This study suggests a forward control system which leads to improved temperature control performances to disturbance signals which could arise from variation of engine load or weather condition. Two dead times in the modelling were described, considering pipe length between the actuator and the engine as well as the thermal process inside the engine. The results of analysis were shown by simulations to confirm responses under different conditions.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.179-180
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• 2011

This paper focuses on the Current-Voltage concurrent control method devoted to the multiple LED (light-emitting diode) string driver. Isolated DC to DC converter with cascaded chopping switch is proposed for smart lighting system such as light with sensor or back light unit of display, which need to control the current of parallel connected multiple LED stings and regulate DC voltage for micro controller for brightness control. The proposed circuit regulates the current of parallel connected multiple LED strings and additional DC voltage output simultaneously. To verify the performance, experimental results are presented based on the prototype board. 5V, 1A voltage mode electric load and two LED strings with different forward voltages are used for output loads. 23W output power is achieved and measured efficiency is in the range of 85%-87%

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.4131-4138
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• 2012

In this paper, we propose a Pedestrian Position Information System(PPIS) using low-cost inertial sensors in GPS-disabled area. The proposed scheme estimates the attitude/heading angle and step detection of pedestrian. Additionally, the estimation error due to the inertial sensors is mitigated by using additional sensors. We implement a portable hardware module to evaluate performance of the proposed system. Through the experiments in indoor building, the estimation error of position information was measured as 2.4% approximately.

• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.328-334
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• 2018

The paper reviews an improved continuous-wave (CW) terahertz (THz) imaging system developed for nondestructive inspection, such as CW-THz quasi-time-domain spectroscopy (QTDS) and interferometry. First, a comparison between CW and pulsed THz imaging systems is reported. The CW-THz imaging system is a simple, fast, compact, and relatively low-cost system. However, it only provides intensity data, without depth and frequency- or time-domain information. The pulsed THz imaging system yields a broader range of information, but it is expensive because of the femtosecond laser. Recently, to overcome the drawbacks of CW-THz imaging systems, many studies have been conducted, including a study on the QTDS system. In this system, an optical delay line is added to the optical arm leading to the detector. Another system studied is a CW-THz interferometric imaging system, which combines the CW-THz imaging system and far-infrared interferometer system. These systems commonly obtain depth information despite the CW-THz system. Reportedly, these systems can be successfully applied to fields where pulsed THz is used. Lastly, the applicability of these systems for nondestructive inspection was confirmed.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.1
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• pp.118-128
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• 2017

In this study, we propose a real time inertial navigation system/global positioning system (INS/GPS) integrated smoothing algorithm based on an extended Kalman filter (EKF) and a position damping loop (PDL) for synthetic aperture radar (SAR). Integrated navigation algorithms usually induce discontinuities due to error correction update by the Kalman filter, which are as detrimental to the performance of SAR as the relative position error. The proposed smoothing algorithm suppresses these discontinuities and also reduces the relative position error in real time. An EKF estimates the navigation errors and sensor biases, and all the errors except for the position error are corrected directly and instantly. A PDL activated during SAR operation period imposes damping effects on the position error estimates, where the estimated position error is corrected smoothly and gradually, which contributes to the real time smoothing and small relative position errors. The residual errors are re-estimated by the EKF to maintain the estimation performance and the stability of the overall loop. The performance improvements were confirmed by Monte Carlo simulations. The simulation results showed that the discontinuities were reduced by 99.8% and the relative position error by 48% compared with a conventional EKF without a smoothing loop, thereby satisfying the basic performance requirements for SAR operation. The proposed algorithm may be applicable to low cost SAR systems which use a conventional INS/GPS without changing their hardware configurations.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.2
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• pp.107-115
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• 2003

PMSM(permanent magnet synchronous motor) are widely used in industrial and home appliance because of their high torque to inertia ratio, superior power density, and high efficiency For the high control performance, accurate information of rotor position Is essential. In recent, sensorless algorithms are much studied due to high cost problem of position sensor and low reliability in harsh environment. In the proposed method, a differential linkage flux is used for the estimation of rotor position. The differential magnetic field flux is calculated by the voltage equations and measured phase current without any integration and differential calculus. Instead of linkage flux calculation with differential operation, a new mathematical differential method is introduced by a-$\beta$ transformation. The proposed novel position sensorless speed control scheme is verified through experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.4
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• pp.344-350
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• 2003

In this paper, an estimation technique of initial rotor position at standstill in Switched Reluctance Motor(SRM) is proposed. In case search coils are used as a position sensor, it has many advantages like low cost, decrease in the volume, high robust characteristics and wide applications. However, the initial rotor position detection is very difficult because the search coil's EMF is not exist at a standstill. In this paper, a near estimation method of initial rotor position is suggested using squared Euclidean distance. The simulation and experiment for the proposed method are achieved. The validity of the proposed method is verified by experimental results.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2526-2531
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• 2005

A practical pinch torque estimator based on the Kalman filter is proposed for low-cost anti-pinch window control systems. To obtain the accurate angular velocity from Hall-effect sensor measurements, the angular velocity calculation algorithm is executed with additional procedures for removing the measurement noises. Apart from the previous works using the angular velocity estimates and torque estimates for detecting the pinched condition, the torque rate is augmented to the system model and the proposed pinch estimator is derived by applying the steady-state Kalman filter recursion to the model. The motivation of this approach comes from the idea that the bias errors in torque estimates due to the motor parameter uncertainties can be almost eliminated by introducing the torque rate state. For detecting the pinched condition, a systematic way to determine the threshold level of the torque rate estimates is also suggested via the deterministic estimation error analysis. Simulation results are given to certify the pinch detection performance of the proposed algorithm and its robustness against the motor parameter uncertainties.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.6
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• pp.1-7
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• 2011

This paper presents implementation and control of a two wheeled mobile robot system which consists of two systems, an inverted pendulum system and a mobile robot system. Control purpose is to regulate its balancing and navigation. The balancing robot has advantages of one point turning and robust balancing against disturbances from the ground. Simulation studies of local and global control methods are performed. Since the robot is implemented to have a symmetrical structure, simple linear control algorithms are used for balancing and navigation. Low cost sensors such as gyro and tilt sensor are fused together to detect the inclined angle. Experimental studies of following desired circular trajectory are conducted.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.166-172
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• 1998

Switched reluctance motor(SRM) has the advantages of simple structure, low rotor inertia and high efficiency. However, position sensor is essential in SRM in order to synchronize the phase excitation to the rotor Position. The Position sensors increase the cost of drive system and tend to reduce system reliability. This paper investigates the speed control of sensorless SRM in which the Phase current and change rate are utilized in position decision, and the period of dwell angle is variable for speed control. The proposed system consists of Position decision circuit, speed controller, digital logic commutator, switching angle controller and inverter The performances in the proposed system are verified through the experiment.