• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.1
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• pp.98-106
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• 2007

This paper represent improved on-line turn off angle control schemes for switched reluctance motors based on current control. For the purpose of finding the optimal commutation switching angle point with improved controller, it is utilized turn on and turn off position calculation with inductance vs. current vs. not linkage analysis method. The goal of proposed paper is the maximization of the energy conversion per stroke and torque ripple reduction and obtaining approximately flat-topped current waveform. The proposed control scheme is demonstrated simulation and on a prototype experimental system.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.4
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• pp.355-361
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• 2011

The power control of the existing heating element has been using the On-Off control, phase control, and PWM control. In case of controlling power PTC heating element developed recently with the existing method, the temperature is unable to be precisely controlled or the harmful electromagnetic wave to human body is generated. In this paper, We suggest the power control of PTC heating cable using variable AC Cycles. This regards the AC cycle of N as the unit of the power control. It determines On-Off for each cycle. It is the AC power control method in which it arranges the on-cycle in N cycles in the random and it supplies the current continuously. At this time. the minimal electric power amount becomes 1/N. The maximum current amount becomes 1 and sets up the number of on cycles according to the set value and can control the electric power with the step of N consistently. In the PTC heating system, we show that proposed power control method is superior in the EMI and temperature control property using MATLAB simulation, experiments and measurements.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.3
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• pp.240-245
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• 2004

This paper presents a Switched Reluctance Motor(SRM) drive using the self-tuning control method to achieve the maximum torque. SRM has the difficulty to research it by an analytic method and to control the speed End torque because of the high nonlinearity. So, in this paper, the self-tuning control method is applied to relevantly controlling turn-on/off angle to operate at the maximum torque. Also, the feedback signals to control the turn-on/off angle are the encoder pulse and the increment of phase current. At first, n adequate turn-off angle is searched by itself and then a turn-on angle is done. As the relationship between turn-on and him-off angle is mutual dependent, the turn-on/off angle is controlled by a real time self-tuning control method in order to maintain the maximum torque. The proposed self-tuning Algorithm is verified by experiments.

• Journal of the Institute of Convergence Signal Processing
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• v.14 no.2
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• pp.130-135
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• 2013

Recently, the needs of system performances such as working speed and processing accuracy in machine tools have been increased. Especially, the working speed increment generates harmful heat at both moving part of the machine tools and handicrafts. The heat is a main drawback to progress accuracy of the processing. Hence, a oil cooler to control temperature is inevitable for the machine tools. In general, two representative control schemes, hot-gas bypass and variable speed control of a compressor, have been adopted in the oil cooler system. In this paper, the compressor's speed are controlled to keep reference value of temperature at oil outlet. The precision processing of a machine tool is required for an oil cooler guaranteeing ${\pm}0.1^{\circ}C$ temperature control. But the oil cooler with precision temperature control is expensive. Therefore in this paper, instead of a on/off(relay) control method, a PID and phase angle electric power control method is proposed for the precision control of an oil cooler. The proposed controller is implemented and tested at the temperature of $23^{\circ}C$, $24^{\circ}C$ and $25^{\circ}C$.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.2
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• pp.17-28
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• 2015

In this paper, it is accomplished to design a control method for such an actuation system of simplified ON/OFF mechanism with actuation command limit. First of all, based on experimental data, the modeling works for nonlinear/linear actuation dynamics are performed, which are govern by PWM command as a control input. Using the linearized model, a classical PI control method is designed to satisfy the aimed control performance requirements, and a control algorithm is proposed to realize the required control performance in the effective control region through resolving the issue for the PWM command limit which reduces the control performance. Finally, through control simulations, the design method is verified and the corresponding control performance improvement is evaluated.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04b
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• pp.1595-1598
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• 2002

최근 정보통신기술의 발달과 인터넷 이용의 폭발적인 성장에 따라 인터넷을 통한 전자 상거래가 새로운 경제 활동으로 등장과 동시에 off-line을 기반으로 하는 전자 상거래 시장이 급속한 성장을 하고 있다. 이에 따라 기존의 on-line 상의 전자 지불 방식을 보다 실용적인 off-line 상의 전자 지불 방식이 요구되고 있다. 전자 지불 방식의 하나인 전자 화폐는 효과적인 응용을 위해 실물 화폐와 유사한 여러 가지 성질을 갖고 있기는 하지만, 이러한 성질 중에서 사용자의 프라이버시를 보장하는 경우 발생하는 부정적인 문제 즉 돈 세탁, 약탈, 그리고 자금의 해외 유출의 용의 등을 문제점을 해결하기 위해 익명성 제어 익명성 취소 등의 다양한 프로토콜의 개발이 연구되고 있다. 이에 따라 본 논문에서는 off-line 상에서 전자상거래를 할 때 부정 사용자에 대한 사용자 추적, 즉 익명성 제어가 가능한 프로토콜을 제안한다. 제안한 프로토콜의 특징은 기존의 on-line 상의 시스템 구현의 효율성을 고려하여 RSA와 Hash 함수만을 사용하여 사용자 은닉이 가능하도록 하였으며, 또한 익명성 제어가 가능하지만 어느 기관 단독이 아는 은행과 인중기관이 협조 할 경우에만 추적이 가능하다.

• Journal of Power System Engineering
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• v.2 no.2
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• pp.55-59
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• 1998

In practice, the property of nonlinearity is contained in all physical systems. In other word, all physical systems are nonlinear to some degree. Therefore it is important that we acquires a facility for analyzing feedback control systems with varying degrees of nonlinearity. To operate the system linearly over wide range of variation of signal amplitude and frequency, the system requires components of an extremely high quality. Such a system would probably be impractical in the view points of cost, space and weight. In this context of view, it is worth noting that the nonlinearities may be intentionally introduced into a system in order to compensate for the effects of other undesirable nonlinearities or to obtain better performance than what could be achieved using linear element only. A simple example of an intentional nonlinearity is the use of a nonlinear damped system to optimize response in accordance with the magnitude of error. In this paper, an on-off type nonlinear controller is introduced and the applicability and validity of a simple on-off controller are presented by the experimental result.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.6
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• pp.473-480
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• 2013

Researches for various lunar landing technologies are in progress for the lunar exploration program planned for early 2020s in Korea. This paper shows the integrated simulation for safe lunar landing guidance/control system in powered descent phase. Generally, the lunar lander uses on/off(bang-bang) controller to control the RCS jet thrusters instead of proportional controller. In this paper, the on/off controller using phase-plane switching function, and thruster selection algorithm to control sixteen thrusters are applied. Also additional guidance commands are calculated by a proposed fuzzy logic guidance algorithm. The simulation results show that lunar lander can follow a reference trajectory which is generated by optimization method, then land on the surface safely.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.868-876
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• 1995

This study deals with a position control of an electro-hydraulic servo system which consist of cylinder and high speed on-off valves operated by microcomputer. The merits of PWM control of hydraulic equipment are the robustness of the high spee on-off valve, its low price and the direct control without D/A converter. In the PWM control of high speed on-off valve, the time lag and switching time existing between the input and output signals of valve are considered as demerit points. To get analytical results, the effects of these demerits have to be clarified in detail. The object of this study is to propose a mathematical model for the behavior of high speed on-off valve and to get analytical results of this system. The dynamic characteristics of this system is examined by digital computer simulation analytically and compared with experimental results to varify the proposed mathematical model.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.16 no.4
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• pp.16-23
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• 2020

In this study, the control characteristics and effects of control methods on heating performance and energy consumption for the hot water floor radiant heating control system of a residential apartment were research by experiment. As a control method, On-Off control and outdoor reset control methods with GRNN(General Regression Neural Network) and without GRNN are considered. Also, the control performances with regard to improvement of indoor thermal environment and reduction of energy consumption are compared, respectively. Experiment results show that the performance of the control method with GRNN is better than that of conventional on-off control method without GRNN in the responses of room set temperature and energy saving.