• International Journal of Control, Automation, and Systems
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• v.3 no.3
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• pp.411-418
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• 2005

This paper discusses an output-tracking control design method for Takagi-Sugeno fuzzy systems with parametric uncertainties. We first represent the concerned system as a set of uncertain linear systems. The tracking problem is then converted into a stabilization problem thereby leading to a more feasible control design procedure. A sufficient condition for robust practical output tracking is derived in terms of a set of linear matrix inequalities. A numerical example for a flexible-joint robot-arm model has been demonstrated, to convincingly show effectiveness of the proposed system modeling and control design.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2001.12a
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• pp.149-152
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• 2001

본 논문은 연속 시간과 이산 시간에서의 스위칭 모드 퍼지 모델 기반 제어기의 새로운 설계 기법에 대해서 논의한다. 스위칭 모드 퍼지 모델 기반 제어기의 설계에는 Takagi-Sugeno(75) 퍼지 시스템이 사용된다. 이 스위칭 모드 퍼지 모델 기반 제어기는 "정복-분할(divide and conquer)"이라는 하향식 접근 방식을 이용한다. 이 방법은 여러 개의 규칙을 가지고 있는 시스템에서 유한의 하위 시스템으로 시스템을 분할하여 각각의 부분 해를 구하고 이들을 결합하여 전체 시스템의 해를 구하는 방법이다. 제어기의 설계 조건은 주어진 75 퍼지 시스템의 안정화를 보장하는 선형 행렬 부등식들(LMls)에 의해 결정된다. 적절한 시뮬레이션 예제를 통한 성능 비교를 통해 본 논문의 우수성을 입증한다.

• Journal of Power Electronics
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• v.19 no.1
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• pp.244-253
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• 2019

Finite control set model-predictive control (FCS-MPC) has received increasing attentions due to its outstanding dynamic performance. It is being widely used in power converters and multilevel inverters. However, FCS-MPC requires a lot of calculations, especially for multilevel-cascaded H-bridge (CHB) static synchronous compensators (STATCOMs), since it has to take account of all the feasible voltage vectors of inverters. Hence, an improved five-segment space vector pulse width modulation (SVPWM) method based on the non-orthogonal static reference frames is proposed. The proposed SVPWM method has a lower number of switching states and requires fewer computations than the conventional method. As a result, it makes FCS-MPC more efficient for multilevel cascaded H-bridge STATCOMs. The partial cost function is adopted to sequentially solve for the reference current and capacitor voltage. The proposed FCS-MPC method can reduce the calculation burden of the FCS-MPC strategy, and reduce both the switching frequency and power losses. Simulation and experimental results validate the excellent performance of the proposed method when compared with the conventional approach.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2231-2242
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• 2016

A simplified model predictive control method is presented in this paper. This method is based on a future reference voltage vector for a three-phase four-leg voltage source inverter (VSI). Compared with the three-leg VSIs, the four-leg VSI increases the possible switching states from 8 to 16 owing to a fourth leg. Among the possible states, this should be considered in the model predictive control method for selecting an optimal state. The increased number of candidate switching states and the corresponding voltage vectors increase the calculation burden. The proposed technique can preselect 5 among the 16 possible voltage vectors produced by the three-phase four-leg voltage source inverters, based on the position of the future reference voltage vector. The discrete-time model of the future reference voltage vector is built to predict the future movement of the load currents, and its position is used to choose five preselected vectors at every sampling period. As a result, the proposed method can reduce calculation load by decreasing the candidate voltage vectors used in the cost function for the four-leg VSIs, while exhibiting the same performance as the conventional method. The effectiveness of the proposed method is demonstrated with simulation and experiment results.

• Journal of Mechanical Science and Technology
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• v.19 no.5
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• pp.1095-1106
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• 2005

Recently, the conventional controller of machine-tool has been increasingly replaced by the PC-based open architecture controller, which is independent of the CNC vendor and on which it is possible to implement user-defined application programs. This paper proposes CNC­implemented fault diagnosis and web-based remote services for machine-tool with open architecture CNC. The faults of CNC machine-tool are defined as the operational faults occupied by over $70{\%}$ of all faults. The operational faults are unpredictable as they occur without any warning. Two diagnostic models, the switching function and the step switching function, were proposed in order to diagnose faults efficiently. The faults were automatically diagnosed through the fault diagnosis system using the two diagnostic models. A suitable interface environment between CNC and developed application modules was constructed for the internal function of CNC. In addition, a suitable web environment was constructed for remote services. The web service functions, such as remote monitoring and remote control, were implemented, and their operability was tested through the web. The results obtained through this research could be a model of fault diagnosis and remote servicing for machine-tool with open architecture CNC.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.6
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• pp.2709-2734
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• 2020

The growing demand to make wireless data services 5G compatible has necessitated the development of an energy-efficient approach for an effective new wireless environment. In this paper, we first propose a cognitive sensor node (CSN) based game theory for deriving energy via a primary user-transmitted radio frequency signal. Cognitive users' time was segmented into three phases based on a time switching protocol: energy harvest, spectrum sensing and data transmission. The proposed model chooses the optimal energy-harvesting phase as the effected factor. We further propose a distributed energy-harvesting model as a utility function via pricing techniques. The model is a non-cooperative game where players can increase their net benefit in a selfish manner. Here, the price is described as a function pertaining to transmit power, which proves that the proposed energy harvest game includes Nash Equilibrium and is also unique. The best response algorithm is used to achieve the green connection between players. As a result, the results obtained from the proposed model and algorithm show the advantages as well as the effectiveness of the proposed study. Moreover, energy consumption was reduced significantly (12%) compared to the benchmark algorithm because the proposed algorithm succeeded in delivering energy in micro which is much better compared to previous studies. Considering the reduction and improvement in power consumption, we could say the proposed model is suitable for the next wireless environment represented in 5G.

• Journal of Information Technology Applications and Management
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• v.14 no.4
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• pp.159-174
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• 2007

The purpose of this research is to investigate the relationships among the perceived satisfaction, the perceived the trust, the commitment, the key features for mobile phone, the brand image, the switching cost and the repurchasing intention. We also examine the differences between Korean and Indonesian markets concerning the relationships of these key successfactors. The structural model is tested with the data form each of the sub-samples (i. e. Korean and Indonesian users taken separately). Properties of the casual paths, including standardized path coefficients, the significance of difference, and variance explained for trust, satisfaction, commitment and repurchasing in the hypothesized model, are presented. This study indicated that hardware (sound quality, LCD display, design) user interface (GUI, Menu, Key pad) and extra functions (camera phone, wireless internet, MP3 player) are the three important factors effecting the trust and the satisfaction. The proposed model has been newly tested from the technological prospective in order to get the more practical result. Following the model test, we conduct a test of the differences in path coefficients between Korean and Indonesian users. MSEM show that, compared to Korean market, Indonesian had more emphasized on extra-function for the mobile phone as well as giving more influence to the satisfaction from the brand image. It means Korean market consider the extra-function as basic or no-premium points. And the satisfaction has been effected by switching-cost in Korea but the trust in Indonesia. Other interesting result from the structural weight invariance indicate that, compared to Korean market, the brand-image has effected the satisfaction in addition to placing more the trust on determining the commitment in Indonesia.

• Bulletin of the Korean Mathematical Society
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• v.38 no.1
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• pp.29-53
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• 2001

This note presents a an indirect adaptive control scheme for first-order continuous-time systems. The estimated plant model is controllable and then the adaptive scheme is free from singularities. The singularities are avoided through a modification of the estimated plant parameter vector so that its associated Sylvester matrix is guaranteed to be nonsingular. That properties is achieved by ensuring that the absolute value of its determinant does not lie below a positive threshold. A modification scheme based on the achievement of a modified diagonally dominant Sylvester matrix of the parameter estimates is also given as an alternative method. This diagonal dominance is achieved through estimates modification as a way to guarantee the controllability of the modified estimated model when a controllability measure of the ‘a priori’ estimated model fails. In both schemes, the use of a hysteresis switching function for the modification of the estimates is not required to ensure the nonsingularity of the Sylvester matrix of the estimates.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.11
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• pp.1130-1137
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• 2006

Relaxed Static Stability(RSS) concept has been applied to improve aerodynamic performance of modern version supersonic jet fighter aircraft. Therefore, the flight control systems are necessary to stabilizes the unstable aircraft and provides adequate handling qualities. The initial production flight control system are verified by flight test and it's always an elements of danger because of flight-critical nature of control law function and design error due to model base design method. These critical issues impact to flight safety, and it could be lead to a loss of aircraft and pilot's life. Therefore, development of an easily modifiable RFCS(Research Flight Control System) capable of reverting to a PFCS(Primary Flight Control System) of reliable control law must be developed to guarantee the flight safety. This paper addresses the concept of SSWM(Software Switching Mechanism) using the fader logic such as TFS(Transient Free Switch) based on T-50 flight control law. The result of the analysis based on non-real time simulation in-house software using SSWM reveals that the flight control system are switching between two computers without any problem.

• Journal of Power Electronics
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• v.17 no.3
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• pp.674-685
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• 2017

The conventional model predictive direct torque control (MPDTC) method uses all of the voltage vectors available from a two level voltage source inverter for the prediction of the stator flux and stator current, which leads to a heavy computational burden. This paper proposes an improved model predictive direct torque control method. The stator flux predictive controller is obtained from an analysis of the relationship between the stator flux and the torque, which can be used to calculate the desired voltage vector based on the stator flux and torque reference. Then this method only needs to evaluate three voltage vectors in the sector of the desired voltage vector. As a result, the computational burden of the conventional MPDTC is effectively reduced. The time delay introduced by the computational time causes the stator current to oscillate around its reference. It also increases the current and torque ripples. To address this problem, a delay compensation method is adopted in this paper. Furthermore, the switching frequency of the inverter is significantly reduced by introducing the constraint of the power semiconductor switching number to the cost function of the MPDTC. Both simulation and experimental results are presented to verify the validity and feasibility of the proposed method.