• Proceedings of the KIEE Conference
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• 2001.07e
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• pp.108-112
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• 2001

Vector control schemes are used in inverter-fed induction motor drives to obtain high performance. Crucial to the success of the vector control scheme is the knowledge of the instantaneous position of the rotor flux. However, the position of the rotor flux change with temperature and magnetic saturation of the motor. This variation cause deterioration of both steady state and dynamic operation of the motor drives. Performance degradation is in the form of input-output torque nonlinearity and saturation of the motor. Analytic expressions are derived to evaluate the effects due to parameter sensitivity.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2161-2163
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• 2002

The PID type controller has been widely used in industrial application doc to its simply control structure, ease of design and inexpensive cost. However control performance of the PID type controller suffers greatly from high uncertainty and nonlinearity of the system, large disturbances and so on. This paper presents a hybrid fuzzy logic proportional plus conventional integral derivative controller (Fuzzy P+ID). In comparison with a conventional PID controller, only one additional parameter has to be adjusted to tune the Fuzzy P+ID controller. In this case, the stability of a system remains unchanged after the PID controller is replaced by the Fuzzy P+ID controller without modifying the original controller parameters. Finally, the proposed hybrid Fuazy P+ID controller is applied to BLDC motor drive. Simulation results demonstrated that the control performance of the proposed controlled is better than that of the conventional controller.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2171-2175
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• 2002

Helicopter dynamics are plenty of nonlinearity. A complete mathematical model including propeller dynamics and fortes generated by the propellers is very difficult to obtain. So the method used to design to design a controller is a parameter estimation. Design controller based on variable structure system. This paper deals with LQR control technique to control efficiently, its elevation angle and azimuth one. The purpose of the experiment is to design a controller allows to use a desired elevation angle and azimuth ones. The system model has a helicopter model with 2-degree-of freedom. The simulation results were verified usefulness of controller.

• KIEE International Transactions on Power Engineering
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• v.5A no.2
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• pp.152-158
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• 2005

This paper describes a reactive optimal power flow incorporating margin enhancement constraints. Margin sensitivity at a steady-state voltage instability point is calculated using invariant space parametric sensitivity, and it can provide valuable information for selection of effective control parameters. However, the weakest buses in neighboring regions have high margin sensitivities within a certain range. Hence, the control determination using only the sensitivity information might cause violation of operational limits of the base operating point, at which the control is applied to enhance voltage stability margin in the direction of parameter increase. This paper applies an interior point method (IPM) to solve the optimal power flow formulation with the margin enhancement constraints, and shunt capacitances are mainly considered as control variables. In addition, nonlinearity of margin enhancement with respect to control of shunt capacitance is considered for speed-up control determination in the numerical example using the IEEE 118-bus test system.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.211-214
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• 1997

This paper describes the position accuracy performance improvement of hybrid type LPM. The harmonics are included in the thrust force component of LPM, those are generated from the the nonlinearity of intrinsic magnetic saturation characteristic and mechanical construction, and so on. In this paper, the performance improvable methode is proposed for the better thrust force by the corrected exciting current injection, and precise position control is achieved.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.306-308
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• 1997

In this paper, We present the transient analysis method of induction motor by TDFE(Time Domain Finite Element) method. For simulation of transient performance, Maxwell's equations are solved using 2-Dimensional TDFE method, and the circuit equations from the stator and rotor are solved simultaneously. The time derivatives are discretized with Euler scheme and the Newton-Raphson iteration method is applied to a large system of equations which are representing the whole magnetic and feeding circuit equations because of the magnetic nonlinearity of the stator and rotor core. The presented method is applied to three phase induction motor. And we obtained the phase currents, torque and rotor position until the steady state.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.3001-3003
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• 2000

In this paper. we propose Fuzzy Self-Organizing Networks (FSON) using both Polynomial Neural Networks(PNN) and Fuzzy Neural Networks(FNN) for model identification of complex and nonlinear systems. The proposed FSON is generated from the mutually combined structure of both FNN and PNN. Accordingly it is possible to consider the nonlinearity characteristics of process and to get the better output performance with superb predictive ability. In order to evaluate the performance of proposed models. we use the nonlinear data sets. The results show that the proposed FSON can produce the model with higher accuracy and more robustness than previous any other method.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.864-867
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• 1998

This is Part I of a two part paper dealing with control design in power systems using the method of normal forms. In stressed power systems, due to the presence of increased nonlinearity and the existence of nonlinear modal interactions. there exist some limitation to the use of conventional linear control design techniques. The objective of this work is to understand the effect of the nonlinear modal interaction on control performance and to develop a procedure to design controls incorporating the nonlinear information. Part II presents the numerical results dealing with the design procedure.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2624-2626
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• 2000

The stabilization controls of coupled tank system and ball-beam system are difficult control tasks because of their high order time delay, nonlinearity and structural unstability. Fuhermore, a series of classical methods such as a conventional PID and a full state feedback controller(FSFC) based on the local linearizations have narrow stabilizable regions. Therefore, in this paper, in order to stabilize two representative nonlinear system mentioned above, a Sliding Mode Controller based on a Real Variable Elitist Genetic Algorithm(RVEGA SMC) was proposed.

• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.564-566
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• 1998

A robot manipulator is a nonlinear time varying MIMO system. Therefore, when a robot manipulator operates at high speeds, the performance of pursuing its trace becomes worse due to the increased nonlinearity of system. Several nonlinear control methods are introduced for solving this problem. But, these methods need a large amount of calculations, so it is necessary to use the controller equipped with a faster and more efficient processing ability. In this paper, we designed the Rhino XR-3 Robot Controller which controls five joints concurrently. To reduce the size of the controller and to control 6 dc-servo motors in real time, we use the TMS320c31, the high-speed digital signal processor.