• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.366-370
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• 1990

Generally, when servo system is used, various sensors are required to have comparison and compensation to the reference value. However, the sensors are relatively expensive, and cannot be always implemented because of the limit of space or the environmental conditions. In this paper, state observer systems without sensors are investigated. State observer systems are required to estimate the states quickly and exactly without being affected by the disturbances. Thus, in this paper, the effects of systems poles and observer poles are studies. In addition, the parameter variations are also considered to evaluate the effect of them to the observer based systems. Also, in this paper a whole system which includes compensators, observers and loads are considered and analysed by using numerical simulations.

• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.179-181
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• 2004

This paper is proposed an adaptive fuzzy-neural network(A-FNN) controller based on the vector controlled induction motor drive system. The hybrid combination of fuzzy control and neural network will produce a powerful representation flexibility and numerical processing capability. Also, this paper is proposed speed estimation of induction motor using A closed-loop state observer. The rotor position is calculated through the stator flux position and an estimated flux value of rotation reference frame. A closed-loop state observer is implemented to compute the speed feedback signal. The results of analysis prove that the proposed control system has strong robustness to rotor parameter variation, and has good steady-state accuracy and transitory response.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.10
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• pp.27-36
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• 2014

Network analysis applications in energy management systems play a key role in the economic and reliable operation of power systems. In order to provide operators with useful network information, the accurate results of topology processing, state estimation, power flow, and contingency analysis must be simulated. This paper proposes a validation methodology of network analysis applications in energy management systems. The energy management systems was checked to ensure that it meets the originally specified functions based on the proposed methodology. In addition, the performance of state estimation is evaluated with the reference of the proposed methodology. The proposed methodology is being conducted by energy management systems and the Korean power systems have been utilized for the test systems.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.54 no.1
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• pp.1-7
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• 2005

This paper is proposed the speed and position sensorless control of surface permanent magnet synchronous motor(SPMSM) with adaptive fuzzy and observer. A adaptive fuzzy controller is applied for speed control of SPMSM drive. A adaptive state observer is used for the mechanical state estimation of the motor. The observer was developed based on nonlinear model of SPMSM, that employs a d - q rotating reference frame attached to the rotor. A adaptive observer is implemented to compute the speed and position feedback signal. The validity of the proposed sensorless scheme is confirmed by various response characteristics.

• Journal of Korean Society of Rural Planning
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• v.5 no.1 s.9
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• pp.56-65
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• 1999

The purpose of this study was to identify remained real state of the village groves in human settlement circle. That was practiced in case of Chinan-Gun region which traditional elements had well been conserved. 33 village groves were found by site survey, reference and interview in Chinan-Gun region. 31 of 51 village groves were clarified as complementing village grove by classification of grove character. It was identified through survey that many were partially destructed by development and human overuse. The results of this study showed general, socio-behavioral characteristics, characteristics of forest state and vegetation structure of village groves in Chinan-Gun region. Length, area, form, type, motive, location, relationship of those were analyzed to identify general characteristics. Facilities, human behavior and ownership of those were analyzed to identify socio-behavioral characteristics. Principal dominant species and appearing rate, height, width, density of those, species diversity of groves were analyzed to identify forest state and vegetation structure. Interrelation between each factor were analyzed and comparative review with previous studies was achieved.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.361-368
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• 2000

In other to examine the compressibility characteristics of cohesive soils in the mouth of the Nakdong river, the oedometer tests were peformed on undisturbed and reconstituted samples obtained by continuous boring typically at 3 different sites. It is meaningful to compare the consolidation behavior of natural clays with a reference state because the natural clays are depending on the stress history, sedimentary environment and geological history. In this study, the insitu state of the Pusan clays was investigated using the concepts of ISL(Nagaraj, 2000) and ICL and SCL(Burland, 1990). And for the purpose of confirming the existence of the underconsolidated clays, a standpipe type piezometer test and a dissipation test by piezocone were performed at their sites. Consequently, the Pusan clays were evaluated as normally consolidated clays.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.6
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• pp.342-350
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• 2003

In this paper, a levitation controller for a magnetic levitation(MagLev) system is designed and implemented. The target to be controlled is PEM(permanent and electromagnet) type with 4-corners levitation which is open-loop unstable, highly non-linear and time-varying system. The digital control system consists of a VME-based CPU board, AD board, PU board, 4-Quadrant chopper, and gap sensor, accelerometer as feedback sensors. In order to estimate the velocity of the magnet, we used 2nd-order state observer with acceleration and gap signal as input and output, respectively. Using the estimated states, a state feedback control law for the plant is designed and the feedback gains are selected by using the pole-placement method. The designed controller is experimentally validated by step-type gap reference change and force disturbance test.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.215-218
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• 1995

In this paper, a sliding mode controller (SMC) which can be characterized by high accuracy, fast response and robustness is applied to speed control of AC-SERVO motor. The control input is changed to continuous one in the boundary layer to reduce the chattering phenomenon, and the boundary layer converges to zero when the state variables of system reach to steady state values. The integral compensator is added to reduce steady state error and to provide the continuous torque reference. The acceleration which is necessary to get the sliding plane is estimated by an observer. Sliding surface is included in control input to enhance the robustness and transient response without increasing sliding mode controller gain. The proposed controller is implemented by DSP(digital signal processor). The effectiveness of the proposed control scheme for speed controller is shown by the real-time experimental results in the paper.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.11a
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• pp.130-134
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• 2001

In the re-entry control system, errors apt to induce because the time derivative of drag acceleration is analytically estimated. Still more, the difficulty of estimation of the exact drag coefficient in hypersonic velocity and the nun-reality of the scale height cause a steady-state drag error. This paper proposes the additional method of the disturbance observer. This reduces the steady-state drag error according to the following series. First, this method estimates a error in drag acceleration time derivative by the analytic calculation and then creates the new drag acceleration time derivative using the estimated error. The performance of the re-entry control system is verified about 32 reference trajectories.

• Journal of The Korean Astronomical Society
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• v.39 no.4
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• pp.147-150
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• 2006

In this paper, initial value problem for dynamical astronomy will be established using parabolic cylindrical coordinates. Computation algorithm is developed for the initial value problem of gravity perturbed trajectories. Applications of the algorithm for the problem of final state predication are illustrated by numerical examples of seven test orbits of different eccentricities. The numerical results are extremely accurate and efficient in predicating final state for gravity perturbed trajectories which is of extreme importance for scientific researches as well as for military purposes. Moreover, an additional efficiency of the algorithm is that, for each of the test orbits, the step size used for solving the differential equations of motion is larger than 70% of the step size used for obtaining its reference final state solution.