• Proceedings of the IEEK Conference
• /
• 1999.06a
• /
• pp.1133-1136
• /
• 1999

A magnetic levitation control system is inherently nonlinear and very unstable. Thus there should be a stabilizing compensator network and a negative feedback path using noncontact photoresistor or ultrasonic sensors for the levitation operation. Since the photo sensor plays a key role in the system, the steady-state error and transient performance of the overall system depend on the characteristics of the sensors. But the sensor itself also suffers from nonlinearity, and the magnitude of sensor input heavily depends on environmental conditions. To improve the output performance, we added a linearizing circuit for the sensor characteristics and a disturbance cancelation circuit to avoid sensitive output due to extraneous interfering light.

• Journal of Institute of Control, Robotics and Systems
• /
• v.13 no.8
• /
• pp.798-803
• /
• 2007

In case of minimized digital camera and mobile digital camera, it's difficult to get the high quality image by conventional AE(Auto Exposure) algorithm because of restriction of system organization. In this paper, a new algorithm that adopts a target setting, a compensation of feedback delay and a gamma correction, etc, are suggested for improving a noise increase and an output sensitivity decrease due to system minimization. We also suggest a method using fuzzy logic which can decide more effectively the ES(Electric Shutter) value and the AGC(Analog Gain Control) value than conventional system.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.7
• /
• pp.1247-1253
• /
• 2008

A design method of a T-S fuzzy model based reduced order nonlinear unknown input observer(NUIO) is presented. The fuzzy NUIO is designed based on the parallel distributed compensation(PDC) concept. It consists of a number of the linear UIOs, each of which is designed for each local linear model in the T-S fuzzy model of a class of nonlinear systems. The fuzzy NUIO provides not only the state estimates insensitive to the unknown inputs, for example, disturbances and faults etc., but also the estimates of the unknown inputs. Therefore, It can be employed in the state feedback control and disturbance rejection control of a class of nonlinear systems with unknown disturbances. It also applied to the robust residual generation for the fault detection and isolation systems and to the design of fault tolerant control systems. As an example, the NUIO is applied to an inverted pendulum system to show the state and disturbance estimation performance and to illustrate the fuzzy reduced order NUIO design method.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.49 no.8
• /
• pp.407-414
• /
• 2000

This paper addresses the analysis and design of fuzzy control systems for a class of complex uncertain single-input single-output nonlinear systems. The proposed method represents the nonlinear system using a Takagi-Cugeno fuzzy model and construct a global fuzzy logic controller by blending all local state feedback controllers with a sliding mode controller. Unlike the commonly used parallel distributed compensation technique, we can design a global stable fuzzy controller without finding a common Lyapunov function for all local control systems, and can obtain good tracking performance by using sliding mode control theory. Furthermore, stability analysis is carried out not for the fuzzy model but for the real nonlinear system with uncertainties. Duffing forced oscillation sysmte is used as an example to show the effectiveness and feasibility of the proposed method.

• Proceedings of the KIEE Conference
• /
• 2002.04a
• /
• pp.155-157
• /
• 2002

Generally, design of feedback circuit for stable system is performed by pole-zero compensation. For the purpose of reliable and stable closed loop system, the compensator would be designed basing upon the analysis of dynamic characteristics. This paper presents analyzed results of dynamic characteristics of the boost input type ZVS converter using active-clamp circuit. The simulated results by using Matlab and the measured results by using HP4194A are presented.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• v.7 no.1
• /
• pp.77-84
• /
• 2007

In this paper, Takagi-Sugeno (TS) fuzzy integral control is investigated to regulate the output voltage of an asymmetric half-bridge (AHB) DC/DC converter; First, we model the dynamic characteristics of the AHB DC/DC converter with state-space averaging method and small perturbation at an operating point. After introducing an additional integral state of the output regulation error, we obtain the $5^{th}$-order TS fuzzy model of the AHB DC/DC converter. Second, the concept of the parallel distributed compensation is applied to design the fuzzy integral controller, in which the state feedback gains are obtained by solving the linear matrix inequalities (LMIs). Finally, simulation results are presented to show the performance of the considered design method as the output voltage regulator and compared to the results for which the conventional loop gain method is used.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.67-67
• /
• 2000

In this paper, a hybrid type fuzzy controller is proposed to maintain molten steel level stable and reliable manner in high speed continuous casting regardless of various disturbances such as casting speed change, tundish weight variation, 치ogging/undoning of SEN(Submerged Entry Nozzle), periodic bulgings, etc. To accomplish this purpose, hardware filter and software filer are carefully designed to eliminate high frequency noise and to smooth input signals from harsh environments. In order to minimize the molten steel level variations from various disturbances the controller uses hybrid type control term: fuzzy logic term, proportional term, differential term and nonlinear feedback compensation tenn. The proposed controller is applied tn commercial mini-mill plant and shows considerable improvement in minimizing the molten steel variation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.274-280
• /
• 2002

This paper addresses the vibration mode shape measurement technique utilizing a Continuous Scanning Laser Doppler Vibrometer (CSLDV). The continuous scanning capability is added to the conventional discrete Laser Doppler Vibrometer by reflecting the laser beams on the surface of the object using two oscillating mirrors. The bow scanning resulted from the proposed scanning method is eliminated by feedback control. The velocity output signal from the CSLDV is modulated to give the spatial velocity distribution in terms of coefficients which are obtained from the Fast Fourier Transformation of the time dependent velocity signal. Using the Chebyshev series form, the analysis of the vibration mode shape techniques for straight Bine scanning and 2 dimensional scanning are presented and discussed. The performance of the proposed SLDV is presented using the experimental results of the vibration mode shape of a plate

• Journal of Sensor Science and Technology
• /
• v.4 no.3
• /
• pp.1-8
• /
• 1995

An electronically compensated current sensor for measurement of power is presented in this paper. An electronic technique which is proposed to design an improved current sensor by means of a feedback winding and an electronic compensation is described. A precision power transducer with a proposed current sensor has been constructed for testing and performance evaluation.

• Proceedings of the KIEE Conference
• /
• 1998.07b
• /
• pp.493-496
• /
• 1998

Several sensorless vector control methods of induction motor have been proposed, but these methods don't have the satisfying performance to the change of the rotor time constant. Therefore, this paper proposes the sensorless vector control method which estimates the rotor speed using MRAS and compensates the rotor time constant using current error feedback at the same time. This method can guarantees the accurate performance of sensorless vector control while the rotor speed and the rotor time constant are changing. This method is verified by computer simulation using SIMULINK in MATLAB.