• Journal of Power Electronics
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• v.5 no.1
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• pp.11-19
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• 2005

This paper describes the two control techniques to perform the sensorless vector control of a PMSM by injecting the high frequency voltage to the stator terminal. The first technique is the estimation algorithm of the initial rotor position. A PMSM possesses the saliency which produces the ellipse of the stator current when the high frequency voltage is injected into the motor terminal. The major axis angle of the current ellipse gives the rotor position information at a standstill. The second control technique is a sensorless control algorithm that injects the high frequency voltage to the stator terminal in order to estimate the rotor position and speed. The rotor position and speed for sensorless vector control is calculated by appropriate signal processing to extract the position information from the stator current at low speeds or standstill. The proposed sensorless algorithm using the double-band hysteresis controller exhibits excellent reference tracking and increased robustness. Experimental results are presented to verify the feasibility of the proposed control schemes. Speed, position estimation and vector control were carried out on the floating point processor TMS320VC33.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.4
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• pp.79-91
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• 1995

Recently, the AC motor which has a simple structure and needs less maintenance has become to be used frequently as a servomotor for position control in the automatic control field. This paper concerns with a method to improve the current and power waveforms of an AC motor, and the current waveforms and 3$\phi$ power waveforms are analyzed by FFT under verious running conditions. The system is composed of a digital bridge inverter, low pass LC filter, and 3$\phi$ AC motor. Through the computer simulations and experiments, it is confirmed that current waveforms and $\phi$ power waveforms con by improved by utilizing the high order low pass LC filter than that of lower order.

• Korean Journal of Organic Agriculture
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• v.7 no.2
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• pp.1-16
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• 1999

In this study, questionnaire were made to environment-friendly producers of apples regarding farm management methods in low-input production method. utilizing organic materials, production and marketing of apples with lower agricultural chemical residues. Besides, five apples farms were visited to find out their management situation by employing the low-input production method in order to protect the environment as well as consumer's health. Those five low-input apple farms were scattered in Kyungbuk, Chungnam, and Chonnam Provinces, There were not many low-input apple farms across the nation from the beginning and, as a result, increasing the sample size was basically very difficult. Most of these farms were using 140hrs of labor per 10a, of which 30hrs in pre-season management, 25hrs in plowing and weed control, 15hrs in disease and pest control, 20hrs in harvest and marketing and 50hrs in miscellaneous activities. Relatively, pest control takes much time in that they would spray pesticides 7-10 times a season to control the apple disease, 9 times on the average. The average gross revenue of low-input apple farms was about \2,000,000/10a, and their average yield was 2,000kg/10a, which are 25% and 13% lower, respectively, than the ordinary apple production case. This means the low-input farmers are inefficient in marketing their products. On the other hand, their production costs were 20.4% higher than the ordinary apple farms on the average. Since the imported foreign fruits including apples must use various agricultural chemicals on their way to the export markets, the domestic low-input apples have competitive edge over them in therms of food safety. In order to improve the low-input apple industry, active cooperation is needed among the producers, government and researchers more than ever. Among other things, production cost reduction and quality improvement with lower chemical residues are part of the urgent matters to be done.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.729-731
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• 2004

This paper deals with the design of a low order $H_{\infty}$ controller by using an iterative linear matrix inequality (LMI) method. The low order $H_{\infty}$ controller is represented in terms of LMIs with a rank condition. To solve the non-convex rank-constrained LMI problem, a linear penalty function is incorporated into the objective function so that minimizing the penalized objective function subject to LMIs amounts to a convex optimization problem. With an increasing sequence of the penalty parameter, the solution of the penalized optimization problem moves towards the feasible region of the original non-convex problem. The proposed algorithm is, therefore, convergent. Numerical experiments show the effectiveness of the proposed algorithm.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.4
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• pp.27-38
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• 1994

In this paper, a simplified model of a hydraulic actuator system for a low-band type active suspension system is derived. To reduce the order of model, time constants of each chamber in hydraulic system are neglected except that of an accumulator. And the dynamics of a spool in the pressure control valve is regarded as a first-order system. The step response and the frequency response of the simplified second-order simulation model exhibit a good agreement with those of the actual system as well as those of the tenth-order simulation model. It is possible to simplify the tenth-order model to the second-order one. The low-band type active suspension model is built up by combining of a quarter car model test rig to testify the validity of the simplified model. The experimental results of suspension characteristics show that the simplified second-order hydraulic actuator model is reasonable to describe the dynamics of the actual hydraulic actuator system for a low-band type active suspension system.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.11
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• pp.786-795
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• 1988

In this paper a boiler control system simulator is designed and inplemeted in order to evaluate performance of the Fault Tolerant Control System. It simulates a boiler control system of a thermal power plant containtng boiler process, peripheral units and analog controller. The simulator uses a low order linear model for boiler first order models for the peripheral unit. Specifically the model of the analog controller is modularized and transformed to digital form if order to be implemented using a micro-processor board. The experimental results show the usability of the developed simulator for the performance test of the FTCS.

• Journal of Korean Society for Atmospheric Environment
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• v.11 no.2
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• pp.153-162
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• 1995

As exhaust emission standards for new passenger cars amended in 1987 have become more stringent, vehicle manufacturers have employed three-way catalyst in order to meet these requirements. The purpose of this study was to gather informations on new emission control systems in customer use for in-use vehicles from the 1987 through 1992 model years were capable of achieving low exhaust emission levels although high levels do occur due to defects, deterioration or maladjustments with the emission control equipment. The vehicles with closed loop electronic control fuel injection system emitted low exhaust emission, but the carburetor control system equipped vehicles emitted high exhaust emissions and the high mileage vehicles exhibited higher average emissions than low mileage vehicles. It was also found that the useful life of 80, 000km is very important to maintain the low emission levels within customer service period.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.473-475
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• 2001

This paper proposed a MPPT ( Maximum Power Point Tracking) control algorithm for PV(Photovoltaic) array based on a modified constant voltage control MPPT algorithm at low-insolation. This method which combines a IncCond(Incremental Conductance) and a constant voltage control algorithm. In contrast to the typical conventional MPPT algorithm, the proposed method have been obtained high efficiency and good performance. The proposed algorithm is verified through simulation result. In order to confirm the availability of the scheme, a simulation used PSIM and ACSL software tool.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.5
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• pp.49-55
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• 2012

In order to derive the efficient utilization of low pressure compressed air fogging system, cooling efficiencies with control types were analyzed through cooling experiments in tomato greenhouses. The control types were set up with temperature control, humidity control, temperature and humidity control, and time control. It showed that the cooling effects were 0.7 to $3.3^{\circ}C$ on average and maximum of 4.3 to $7.0^{\circ}C$, the humidification effects were 3.5 to 13.5 % on average and maximum of 14.3 to 24.4 %. Both the cooling and humidification effect were the highest in the time control method. The cooling efficiency of the air fogging system was not high with 8.3 to 27.3 % on average. However, the cooling efficiency of 24.6 to 27.3 % which appears from the time control is similar to the cooling efficiency of high pressure fogging system experimented in Japan. The air fogging system is operated by low pressure, but its efficiency is similar to high pressure. We think because it uses compressed air. From this point of view, we suggest that the air fogging system can get the cooling efficiency of similar levels to that of high pressure fogging system and it will have an advantage from clogging problem of nozzle etc.

• International Journal of Automotive Technology
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• v.7 no.3
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• pp.369-375
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• 2006

This paper describes a simple proportional and integral control algorithm for a swirl motor controller and its application. The control algorithm may be complicated in order to have desired performance, such as low steady state errors, fast response time, and relatively low overshoot. At the same time, it should be compact so that it can be easily implemented on a low cost microcontroller, which has no floating-point calculation capability and low computing speed. These conflicting requirements are fulfilled by the proposed control algorithm which consists of a gain scheduling proportional controller and an anti-windup integral controller. The mechanical friction, which is caused by gears and a return spring, varies very nonlinearly according to the angular position of the system. This nonlinear static friction is overcome by the proportional controller, which has a two-dimensional look up gain table. It has error axis and angular position axis. The integral controller is designed not only to minimize the steady state error but also to avoid the windup effect, which may be caused by the saturation of a motor driver. The proposed control algorithm is verified by use of a commercial product to prove the feasibility of the algorithm.