• 제어로봇시스템학회논문지
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• 제13권6호
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• pp.581-588
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• 2007

In this paper, we propose a delayed feedback guaranteed cost controller design method for linear time-delay systems with norm-bounded parameter uncertainties and nonlinear perturbations. A quadratic cost function is considered as the performance measure for the given system. Based on the Lyapunov method, an LMI optimization problem is formulated to design a controller such that the closed-loop cost function value is not more than a specified upper bound for all admissible system uncertainties and nonlinear perturbations. Numerical example show the effectiveness of the proposed method.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제8권2호
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• pp.151-157
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• 2008

A non-fragile guaranteed cost control (GCC) problem is presented for a class of discrete time-delay nonlinear systems described by Takagi-Sugeno (T-S) fuzzy model. The systems are assumed to have norm-bounded time-varying uncertainties in the matrices of state, delayed state and control gains. Sufficient conditions are first obtained which guarantee that the closed-loop system is asymptotically stable and the closed-loop cost function value is not more than a specified upper bound. Then the design method of the non-fragile guaranteed cost controller is formulated in terms of the linear matrix inequality (LMI) approach. A numerical example is given to illustrate the effectiveness of the proposed design method.

• 품질경영학회지
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• 제19권2호
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• pp.158-165
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• 1991

The Q-cost has been used in the manufacturing company to decide the optimal level of company's product quality, and to evaluate the effect of company's quality control system since the advent of Q-cost theory. In spite of the following costs are generated in the user side, owing to an unsuitable level of product quality and inadequacy of company's quality control system, these costs are not usually included in the company's Q-cost : (1) the cost generated in relation to a claim proposal as traffic expeneses and transpotation of the product. (2) the cost of maintenance through the useful life of the product, especially accured after quality warranty period. (3) the cost related to the economical efficiency in using the product. (4) the cost ralated to a customer dissatisfaction for the product quality. In this point of view, the contents of user side Q-cost, and the relations between the user side Q-cost and the level of company's product quality are discussed. And then the importance of user side Q-cost in order to determine the optimal quality level is discussed.

• 설비공학논문집
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• 제17권2호
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• pp.156-164
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• 2005

A comparative analysis of an ice storage system has been performed on the operation cost for the four control strategies, i.e., chiller priority and chiller downstream, chiller priority and chiller upstream, storage priority and chiller upstream, storage priority and chiller downstream. Main components of the ice storage system are an ice-on-coil storage tank and a screw compressor chiller. With the simulation program, the operation cost has been evaluated from the economics of an ice storage system. It is found that the operation cost of the ice storage system is strongly dependent on the control strategy, i.e., chiller priority or storage priority, but less affected by the arrangement method, i.e., chiller upstream or chiller downstream. In case of the maximum load day, the control strategy with chiller priority and chiller upstream is supposed to obtain the reduction of operation cost. However, it is found that the control strategy with storage priority and chiller downstream is the best economical operation for most summer seasons except the maximum load day.

• 전기학회논문지
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• 제60권11호
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• pp.2176-2181
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• 2011

This paper estimates the life cycle cost(LCC) of a propulsion control system using the maintenance information in the high speed train(KTX-1). Life cycle costing is one of the most effective approaches for the cost analysis of long-life systems such as the KTX-1. Until now, most life cycle cost of the system has been studied as a whole system viewpoint. But in case of railway industry, LCC studies are needed on the subsystem like a propulsion control system because subsystems are developed continuously localization. This paper proposes the life cycle cost model which fitted to estimate life cycle cost (LCC) using maintenance information manual. As a result, LCC on propulsion control system increased moderately expect for periodical time when major parts are replaced at the same time. Results will be reflected in the development of domestic products.

• 산업경영시스템학회지
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• 제26권1호
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• pp.7-16
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• 2003

At present, company has to produce a product that consumer like with a competitive price, a good quality, and a fitting time to supply. Process control and quality control are very important to supply with a product uniformly and inexpensively. Process control is given much weight in the quality control in manufacturing system. Statistical process controls(SPC) that are used in process generally have major impact on manufacturing, product design activities, and process development potentially. Control charts in statistical process control method can be interpreted the data from quality characteristics in production process and discriminated between chance variation and assignable variation in process. In addition, control chart can be used to monitor the process output and detect when changes in the inputs are required to bring the process back to an in-control state. The models that relate the influential inputs to process outputs help determine the nature and magnitude of the adjustments required. In this paper, the characteristic of product quality is monitored by control chart during the machining process and construction of quality control cycle is considered to divide into two types in this case that different assignable causes lead to shifts having different magnitudes. Then we are intended to find a process shift magnitude which has economical quality cost policy and are considered to quality cost functions to find a process shift magnitude. Those costs are categorized into the well-known categories of prevention, appraisal, and internal failure and external failure. This paper ends with numerical examples that demonstrate the usefulness of the model.

• Journal of Power Electronics
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• 제19권1호
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• pp.168-178
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• 2019

Discrete space vector modulation (DSVM) is an effective method to improve the steady-state performance of the finite control set predictive control for permanent magnet synchronous motor drive systems. However, it requires complex computations due to the presence of numerous virtual voltage vectors. This paper proposes an improved finite control set model-free predictive control using DSVM to reduce the computational burden. First, model-free deadbeat current control is used to generate the reference voltage vector. Then, based on the principle that the voltage vector closest to the reference voltage vector minimizes the cost function, the optimal voltage vector is obtained in an effective way which avoids evaluation of the cost function. Additionally, in order to implement double-objective control, a two-level decisional cost function is designed to sequentially reduce the stator currents tracking error and the inverter switching frequency. The effectiveness of the proposed control is validated based on experimental tests.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.44.1-44
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• 2002

This paper is concerned with the problem of designing a guaranteed cost state feedback controller for singular systems with time-varying delays. The sufficient condition for the existence of a guaranteed cost controller, the controller design method, and the optimization problem to get the upper bound of guaranteed cost function are proposed by LMI(linear matrix inequality), singular value decomposition, Schur complements, and change of variables. Since the obtained sufficient conditions can be changed to LMI form, all solutions including controller gain and upper bound of guaranteed cost function can be obtained simultaneously.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1986년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 17-18 Oct. 1986
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• pp.367-369
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• 1986

Guaranteed cost control is a method applicable to a class of systems with uncertain parameters that guarantees an upper bound of the cost functional. This paper is concerned with a matrix decomposition technique used to yield a reasonable upper bound of the cost functional for a finite-time LQ regulator problem. The uncertain linear systems dealt with in this paper are described by a set of state equations of single-input phase-variable canonical form which contain unknown but bounded uncertain parameters.

• 설비공학논문집
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• 제29권11호
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• pp.592-604
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• 2017

A chiller, having a thermal storage system, can contribute to load-leveling and can reduce the cost of electricity by using electricity at night. In this study, the control experiments and simulations are conducted using both conventional and advanced methods for the building cooling system. Advanced approaches, such as the "region control method", divide the control region into five zones according to the size of the building load, and determines the cooling capacities of the chiller and thermal storage. On the other hand, the "dynamic programming method" obtains the optimal cooling capacities of the chiller and thermal storage by selecting the minimum-cost path by carrying out repetitive calculations. The "thermal storage priority method" shows an inferior chiller performance owing to the low-part load operation, whereas the chiller priority method leads to a high electric cost owing to the low utilization of thermal storage and electricity at night. It has been proven that the advanced control methods have advantages over the conventional methods in terms of electricity consumption, as well as cost-effectiveness. According to the simulation results during the winter season, the electric cost when using the dynamic programming method was 6.5% and 8.9% lower than that of the chiller priority and the thermal storage priority methods, respectively. It is therefore concluded that the cost of electricity utilizing the region control method is comparable to that of the dynamic programming method.