• Journal of Institute of Control, Robotics and Systems
• /
• v.20 no.12
• /
• pp.1231-1237
• /
• 2014

This paper proposes a reduced-order disturbance observer based coordinated tracking controller for uncertain heterogeneous multi-agent systems. To this end, first the control problem is converted as a robust control problem. Then, a dynamic coordinated controller is designed based on the recently proposed reduced-order disturbance observer. Simulation results are given to show the effectiveness of the proposed control scheme.

• The Journal of the Acoustical Society of Korea
• /
• v.13 no.4
• /
• pp.77-85
• /
• 1994

In this study an adaptive algorithm with optimum convergence factor for steepest descent method is proposed, which controls automatically the filter order to take the appropriate level. So far, fixed order filters have been used when adaptive filter is employed according to the priori knowledge or experience in various adaptive signal processing applications. But, it is so difficult to know the filter order needed in real implementations that high order filters have to be performed. As a result, redundant calculations are increased in the case of high order filters. The proposed variable length optimum convergence factor (VLOCF) algorithm takes the appropriated filter order within the given one so that the redundant calculation is decreased to get the enhancement of convergence speed and smaller convergence error during the steady state. The proposed algorithm is evaluated to prove the validity by computer simulation for system Identification.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.14 no.1
• /
• pp.185-190
• /
• 2019

This study aims to apply the mathematical method of fractional order derivatives to the controller that controls the system response. In general, the Laplace transform of the PID controller has an exponent of the integer order of s. The derivative of the fractional order has a fractional exponent of s when it is transformed by Laplace transform. Therefore, this controller proposes a design method with the result of discrete time conversion. Because controllers with fractional exponents of s are not easy to design. This controller is applied to a standard secondary system and its performance is examined. Then, it applies to solenoid valve which is widely used in industrial field. A Luenberger's observer was designed to estimate the disturbance state and the observed state was applied to the fractional order controller. As a result, uniform and precise control performance was obtained. It was confirmed that the position error of the steady state is within 0.1 [%] and the rising time is within about 0.03 [s].

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.18 no.9
• /
• pp.1368-1375
• /
• 1993

This paper deals with the decentralized robust adaptive controller design for large-scale interconnected systems. We consider an arbitrary interconnection of subsystems with unkown parameters and bounded disturbances. When the disturbance and uncertain interconnections are present, the stability of the controlled large scale system is ensured if there exists a positive definite M-matrix which is related to the bound of the interconnections. The possible bound of the interconnections is assumed to be known Pth order polynomials for the decentralized adaptive controller. A modified adaptive law is proposed guaranteeing the existence of a region of attraction from which all signals converge to a residual set Do, which contains the equilibrium.

• Proceedings of the IEEK Conference
• /
• 2007.07a
• /
• pp.93-94
• /
• 2007

이 논문은 시간도약 다중접속(time hopping multiple access: THMA) 초광대역(ultra wideband: UWB) 시스템에서 Modified Hermite Polynomial(MHP)을 기저펄스로 사용하는 M진 고속전송 기법을 제안하고, 시스템의 성능을 분석한다. MHP 펄스 차수들의 상호간 직교성을 이용하여 서로 다른 차수의 MHP 기저펄스 N개를 선형결합하여 M진으로 전송한다. MHP 기저펄스의 상호상관 함수를 구하여 제안하는 M진 시스템의 이론적인 성능을 분석하고, 모의실험을 통해서 기존의 M진 전송에 비해서 시스템의 비트오류확률(bit error rate: BER)이 개선됨을 보인다.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.11
• /
• pp.1-8
• /
• 2008

In this paper, we analyze the symbol error rate (SER) performance of maximum likelihood (ML) joint detection in downlink multiple-input multiple-output (MIMO) multicarrier code division multiple access (MC-CDMA) systems by deriving a tight union bound on the symbol error rate (SER). The union bound for ML joint detection is utilized to demonstrate the performance of MIMO MC-CDMA systems quantitatively in multiuser and frequency selective Rayleigh fading environments. An analysis of the diversity order of the systems shows the effects of multiple users, spread subcarriers, and multiple antennas on the ML joint detection performance. Furthermore, the analysis shows that MIMO MC-CDMA systems without full loading can achieve more diversify than MIMO orthogonal frequency division multiplexing (OFDM) systems.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.2
• /
• pp.276-281
• /
• 2008

This paper proposes a new sliding surface which can have the same dynamics of nominal system based on SVM(Support Vector Machines). The conventional sliding mode control can not have the properties of $H_{\infty}$ controller because its sliding surface has lower order dynamics than the original system. The additional states must be used to solve this problem. However, The sliding surface of this paper can have the dynamics of $H_{\infty}$ control system by using support vector machines without defining any additional dynamic state. By using SVM, the property of $H_{\infty}$ control system can be estimated as a relationship between the states. With this relationship, a new sliding surface can be designed and have $H_{\infty}$ control system properties. As a result, in spite of the parameter uncertainty, the proposed controller can have the same dynamic of nominal system controlled by $H_{\infty}$ controller.

• Journal of Aerospace System Engineering
• /
• v.18 no.2
• /
• pp.71-78
• /
• 2024

During the initial thermal design process, determining the thermal effect of various design variables in a complex orbital thermal environment is time-consuming. To save time in the initial design phase, it is necessary to quickly derive optimal design parameters and predict the temperature. To address these challenges, Veritrek, a software specialized in optimal design using a reduced-order model (ROM), was released in 2018. In this paper, we utilized the Veritrek software to build a reduced-order model, conduct sensitivity analysis, and perform optimal design analysis for a graphite sheet-based cryogenic cooler thermal control system. The goal was to determine the optimal design values for the number of graphite sheet layers, radiator area, and thickness that would meet the allowable temperature of the cryogenic cooler.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2004.04a
• /
• pp.288-291
• /
• 2004

기존의 SOFPNN은 데이터 수가 적고 비선형 요소가 많은 시스템에 대한 체계적이고 효율적인 최적 모델 을 구축할 수 있었으며 각 층 노드의 선택 입력을 변화시킴으로써 네트워크 구조 전체의 적응능력을 향상 시켰다. SOFPNN의 구조는 퍼지 다항식 뉴론(FPN)들로 구성되어 있으며, 층이 진행하는 동안 모델 스스로 노드의 선택과 제거를 통해 최적의 네트워크 구조를 생성할 수 있는 유연성을 가지고 있다. 그러나, 노드의 입력변수의 수와 규칙 후반부 다항식 차수 그리고 입력변수는 설계자의 경험 또는 반복적인 학습을 통해 선호된 네트워크 구조를 선택하였으나, 최적의 네트워크 구조를 구축하는데는 어려옴이 내재되어 있었다. 본 논문에서는 자기구성 퍼지 다항식 뉴럴네트워크(Self-Organizing Fuzzy Polynomial Neural Networks： SOFPNN)을 최적화시키기 위해 유전자 알고리즘을 이용하여 자기구성 퍼지 다항식 뉴럴 네트워크의 입력변수의 수와 이에 해당되는 입력변수 그리고 규칙 후반부 다항식의 차수를 탐색하여 최적 의 자기구성 퍼지 다항식 뉴럴 네트워크를 구축한다. 따라서 모델 구축에 있어서 유연성과 정확성을 가지며 객관적이고 좀 더 정확한 예측 능력을 가진 SOFPNN 모델 구조를 구축할 수가 있다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2004.04a
• /
• pp.303-306
• /
• 2004

기존의 퍼지 규칙에 기반을 둔 퍼지 다항식 뉴론(FPN)들로 구성된 SOFPNN은 데이터 수가 적고 비선형 요소가 많은 시스템에 대한 체계적이고 효율적인 최적 모델 을 구축할 수 있었으며 각 층 노드의 선택 입력을 변화시킴으로써 네트워크 구조 전체의 적응능력을 향상 시켰다. 유전자 알고리즘을 이용하여 자기구성 퍼지 다항식 뉴럴 네트워크의 입력변수의 수와 이에 해당되는 입력변수 그리고 규칙 후반부 다항식의 차수를 탐색하여 최적 의 자기구성 퍼지 다항식 뉴럴 네트워크를 구축한다. 그러나, SOFPNN의 기본 뉴론인 퍼지 규칙 기반 다항식 뉴론의 경우 입력변수가 많아질수록 규칙수가 기하급수적으로 증가한다는 단점을 가지고 있으나 본 노문에서 제안한 퍼지 집합 기반 다항식 뉴론(FSPN)의 규칙수는 입력 변수들이 서로 독립적이므로 규칙의 증가가 퍼지 규칙 기반 다항식 뉴런보다는 적다는 장점을 가지고 있다. 이러한 특성을 기반으로 기존의 SOFPNN의 노드에 퍼지 규칙 기반 다항식 뉴런 대신에 퍼지 집합 기반 다항식 뉴런을 적용한 SOFPNN을 제안하여 기존의 SOFPNN과 성능을 비교하였다. 최적의 자기 구성 퍼지 집합기반 다항식 뉴럴 네트워크를 구축하기 위하여 SOFPNN에서처럼 유전자 알고리즘을 이용하여 네트워크의 입력변수의 수와 이에 해당되는 입력변수 그리고 규칙 후반부 다항식의 차수를 탐색하였다.