• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2002년도 ICCAS
• /
• pp.86.6-86
• /
• 2002

This work presents a study on development of a practical and quantitative technique for assessment of the healthy state of a structure by piezoelectric impedance-based technique associated with longitudinal wave propagation measuring method. A truss structure embedded with piezoelectric patches is investigated for a fundamental study on estimation of the looseness of bolts in the joint. In order to evaluate the minute mechanical impedance change due to loosening bolt, a harmonic longitudinal elastic wave is applied to the structure by a pair of PZT patches and their electric impedance is measured simultaneously. According to the experimental results, the change of the electric impedance of P...

• 제어로봇시스템학회논문지
• /
• 제4권1호
• /
• pp.76-81
• /
• 1998

This paper presents an on-line scheme for parameter estimation of continuous-time systems, based on the model adjustment technique and the genetic algorithm technique. To deal with the initialisation and unmeasurable signal problems in on-line parameter estimation of continuous-time systems, a discrete-time model is obtained for the linear differential equation model and approximations of unmeasurable states with the observable output and its time-delayed values are obtained for the nonlinear state space model. Noisy observations may affect these approximation processes and degrade the estimation performance. A digital prefilter is therefore incorporated to avoid direct approximations of system derivatives from possible noisy observations. The parameters of both the model and the designed filter are adjusted on-line by a genetic algorithm, A set of simulation works for linear and nonlinear systems is carried out to demonstrate the effectiveness of the proposed method.

• 한국지능시스템학회:학술대회논문집
• /
• 한국퍼지및지능시스템학회 1997년도 추계학술대회 학술발표 논문집
• /
• pp.350-355
• /
• 1997

The problem of mathematical model for an unknown system by measureing its input-output data pairs is generally referred to as state estimates. The state estimation problem is often of importance in its own right since we may want to know the value of the states. For instance, in navigation, we may take noisy positional fixes using satelite or radar navigation, and the estimator can use these measurements to provide accurate estimates of current position, hedaing, and velocity. And the state estimates can also be used for control purposes. Then it is very important to know the state of plant. In this paper, the theory of the minimization of a loss function was used to design the fuzzy system. Here, the used teory is Least Square Esimation method. This parametrization has the Linear in the parameters charcteristic that allows standard parameter estimation technique to be used to estimate the parameters of the fuzzy system. The combination of the fuzzy system and the estimation m thod then performs as a nonlinear estimator. If several fuzzy label are defined for the input variables at the antecedent part, the fuzzy system then behaves as a collection of nonlinear estimators where different regions of rules have different parameters. In simulation results, the fuzzy model controlled a difference in the structure between the actual plant and the fuzzy estimator. It is also proved that the fuzzy system is equivalent to its transformed system. therefore we was able to get the state space equation of system with the estimated paramater.

• Journal of information and communication convergence engineering
• /
• 제9권5호
• /
• pp.510-514
• /
• 2011

To detect the insulator in the fault state on the electric poles, we first measured radiation sounds from normal state insulators and error state insulators in the anechoic chamber. We processed the signals in frequency domain to find the features with filter bank, narrow band and wide band analysis. So we could found two apparent results from their frequency spectrums - one was 120Hz harmonic components, the other was high average noise level than normal state ones. Then we also introduced a technique for the direction detection of the fault state insulator using the cross correlation from the three dimensional array microphones. To eliminate the noise signal from unexpected directions, we suggested the zero padding technique in cross correlation function. From these, we could conclude that acoustic fault detection techniques are useful of the detection of insulators' faults and the estimation of the direction of the fault state insulators.

• Wind and Structures
• /
• 제7권3호
• /
• pp.173-186
• /
• 2004

Flutter derivatives provide the basis of predicting the critical wind speed in flutter and buffeting analysis of long-span cable-supported bridges. In this paper, one popular stochastic system identification technique, covariance-driven Stochastic Subspace Identification(SSI in short), is firstly presented for estimation of the flutter derivatives of bridge decks from their random responses in turbulent flow. Secondly, wind tunnel tests of a streamlined thin plate model and a ${\Pi}$ type blunt bridge section model are conducted in turbulent flow and the flutter derivatives are determined by SSI. The flutter derivatives of the thin plate model identified by SSI are very comparable to those identified by the unifying least-square method and Theodorson's theoretical values. As to the ${\Pi}$ type section model, the effect of turbulence on aerodynamic damping seems to be somewhat notable, therefore perhaps the wind tunnel tests for flutter derivative estimation of those models with similar blunt sections should be conducted in turbulent flow.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 학술대회 논문집 전문대학교육위원
• /
• pp.185-190
• /
• 2006

Frequency and phasor are the most important quantities in power system operation because they can reflect the whole power system situation. Frequency reflects the dynamic energy balance between load and generating power, while operators use phasor to constitute the state of system and, moreover, phasor based line relays are currently used in most power systems. So frequency and phasor are regarded as indices for the operating power systems in practice. The proposed technique is suitable for estimation near-nominal, nomina), and off-nominal frequencies. It is useful in designing microprocessor-based relays and meters that need to measure power system frequency. Performance test results, using signals from EMTP source and Excel program, indicate that the proposed technique can provide accurate estimates within 16ms. Maximum estimation errors observed during testing are of the order of 0.006Hz for nominal, near-nominal, and off-nominal frequencies. The proposed technique provides accurate estimates in presence of noise and harmonics and in case ground fault. The rate change of the phase angle is used for estimation. To confirm the validity of the proposed algorithm, the simulation studies carried out on a typical 154[KV] double T/L system by using EMTP software. Some test results are presented in the paper.

• Journal of Electrical Engineering and Technology
• /
• 제6권4호
• /
• pp.439-446
• /
• 2011

Frequency is an important operating parameter for the protection, control, and stability of a power system. Thus, it must be maintained very close to its nominal frequency. Due to the sudden change in generation and loads or faults in a power system, however, frequency deviates from its nominal value. An accurate monitoring of the power frequency is essential for optimum operation and prevention of wide area blackout. Most conventional frequency estimation schemes are based on the DFT filter. In these schemes, the gain error could cause defects when the frequency deviates from the nominal value. We present an advanced frequency estimation technique using gain compensation to enhance the DFT filter-based technique. The proposed technique can reduce the gain error caused when the frequency deviates from the nominal value. Simulation studies are performed using both the data from EMTP-RV software and the user-defined arbitrary signals to demonstrate the effectiveness of the proposed algorithm. Results show that the proposed algorithm achieves good performance under both steady state tests and dynamic conditions.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제53권8호
• /
• pp.545-550
• /
• 2004

This paper is proposed a fuzzy neural network 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 estimation and control of speed of induction motor using ANN Controller. The back propagation neural network technique is used to provide a real time adaptive estimation of the motor speed. The error between the desired state variable and the actual one is back-propagated to adjust the rotor speed, so that the actual state variable will coincide with the desired one. The back propagation mechanism is easy to derive and the estimated speed tracks precisely the actual motor speed. This paper is proposed the theoretical analysis as well as the simulation results to verify the effectiveness of the new method.

• 한국컴퓨터정보학회논문지
• /
• 제29권9호
• /
• pp.9-23
• /
• 2024

본 연구에서는 3차원 보행 데이터 기반 체질량지수(Body Mass Index, BMI) 추정 기술의 분류 정확도를 향상시킬 수 있는 방법을 제안한다. BMI 추정 기술에 관해 기존 연구에서는 BMI 분류 정확도가 약 60%에 불과했다. 이에 본 연구에서는 먼저 BMI 분류 정확도가 낮았던 원인을 규명한다. 본 연구의 분석 결과에 따르면, 그 원인은 보행 데이터 세트의 클래스 불균형(Class Imbalance) 문제를 해결하기 위해 언더샘플링(Undersampling) 기법을 사용한 것에 있었다. 이에 본 연구에서는 언더샘플링 기법 대신 오버샘플링(Oversampling) 기법을 적용해 클래스 불균형 문제를 해결하는 것을 제안한다. 또한, 보행 데이터 기반 BMI 추정 기술에서 인체 측정학(Anthropometric) 특징과 시공간적(Spatiotemporal) 특징의 유용성을 재입증한다. 기존 연구에서는 언더샘플링 기법이 적용된 상태에서 인체 측정학 특징과 시공간적 특징의 유용성이 평가됐고, 두 특징을 함께 사용하면 단독으로 사용했을 때보다 BMI 추정 성능이 낮아진다고 보고됐다. 하지만 본 연구 결과에 따르면, 두 특징을 함께 사용하고 오버샘플링 기법을 적용했을 때 BMI 추정 문제에서 92.92%의 정확도로 SOTA(State-Of-The-Art) 성능을 달성하는 것을 보인다.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국내학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
• /
• pp.187-191
• /
• 1988

To track the manenvering target and to derive the Filter using state estimation and information in real time, we derive adaptive Kalman Filter which reinitialize the internal filter mode.