• Korean Journal of Mathematics
• /
• v.6 no.1
• /
• pp.27-46
• /
• 1998

We are concerned with an optimal control problem governed by a Poisson equation in which body force acts like a control parameter. The cost functional to be optimized is taken to represent the error from the desired observation and the cost due to the control. We recast the problem into the mixed formulation to take advantage of the minimax principle for the duality method. The existence of a saddle point for the Lagrangian shall be shown and the optimality system will be derived therein. Finally, to attain an optimal control, we combine the optimality system with an operational technique. By achieving the gradient of the cost functional, a convergent algorithm based on the projected gradient method is established.

• Journal of IKEEE
• /
• v.22 no.3
• /
• pp.716-722
• /
• 2018

This paper presents a voltage angle control strategy for surface permanent magnet synchronous motor (SPMSM) drives used in low-cost applications, wherein a current vector control is not employed. In the proposed method, the current vector control scheme, which requires high precision phase-current sensing units and a fast calculation capability of a motor drive controller, is replaced with the voltage angle controller. The proposed voltage angle controller calculates a d-axis voltage command to make the d-axis current zero by using a simple equation obtained from the voltage equation of SPMSM. The proposed method shows performance similar to the current vector controlled SPMSM drive during steady-states and its structure is very simple and thus it can be easily implemented with a low-cost microcontroller. The effectiveness of the proposed method is verified through simulations and experiments.

• Smart Structures and Systems
• /
• v.15 no.3
• /
• pp.609-625
• /
• 2015

Management of infrastructure stock is essential in sustainability of society, and its analysis and optimization are studied in the light of control system modeling in this paper. At the first part of the paper, cost of stock management is analyzed based on macroscopic statistics on infrastructure stock and economical growth. Stock management burden relative to economy is observed to become larger at low economic growth periods in developed economies. Then, control system modeling of stock management is introduced and by augmenting maintenance actions as control input, dynamic behavior of stock is simulated and compared with existing time history statistics. Assuming steady state conditions, applicability of the model to cross sectional data is also demonstrated. The proposed model is enhanced so that both preventive and corrective maintenance can be included as system inputs, i.e., feedforward and feedback control inputs. Optimal management strategy to achieve specified deteriorated stock level with minimal cost, expressed in terms of preventive and corrective maintenance actions, is derived based on estimated parameter values for corrosion of steel bridges. Relative cost effectiveness of preventive maintenance is shown when target deteriorated stock level is lower.

• Journal of Power Electronics
• /
• v.19 no.2
• /
• pp.497-508
• /
• 2019

The predictive speed control (PSC) strategy can realize the simultaneous control of speed and current by using one cost function. As a model-based control method, the performance of the PSC is vulnerable to model mismatches such as load torque disturbances and parameter uncertainties. To solve this problem, this paper presents a robust predictive speed control (RPSC) strategy for surface-mounted permanent magnet synchronous motor (SPMSM) drives. The proposed RPSC uses extended state observers (ESOs) to estimate the lumped disturbances caused by load torque changes and parameter mismatches. The observer-based prediction model is then compensated by using the estimated disturbances. The introduction of ESOs can achieve robustness against predictive model uncertainties. In addition, a modified cost function is designed to further suppress load torque disturbances. The performance of the proposed RPSC scheme has been corroborated by experimental results under the condition of load torque changes and parameter mismatches.

• Korean Journal of Construction Engineering and Management
• /
• v.12 no.4
• /
• pp.79-87
• /
• 2011

Cost control is an exceedingly fundamental and important construction business function. Even though enormous research efforts have been exerted in this area, there has been no comprehensive and quantitative study exploring detailed cost control practice of construction companies in terms of practical patterns and trends. This paper identified the variables for practical cost control process first. A survey questionnaire was developed and used in order to collect data from Korean general contractors. Survey results analyzing responses from 45 companies show that engineering aspects of cost management has recently been strongly stressed in the construction industry. Applying various types of progress measurement method are getting popular, and the level of details in collecting job site cost data are prevalent. Cost forecasting are performed more frequently. These trends indicates the recent efforts by Korean general contractors to achieve competitive advantages in the globalized market.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.46 no.3
• /
• pp.15-21
• /
• 2009

In this paper, we consider the design problem of robust stabilization and robust guaranteed cost state feedback controller for discrete-time singular systems with parameter uncertainties by LMI(linear matrix inequality) approach without semi-definite condition and decomposition of system matrices. The objective of robust stabilization controller is to construct a state feedback controller such that the closed-loop system is regular, causal, and stable. In the case of robust guaranteed cost control, the optimal value of guaranteed cost and controller design method are presented on the basis of robust stabilization control technique. Finally, a numerical example is provided to show the validity of the design methods.

• Journal of the East Asian Society of Dietary Life
• /
• v.2 no.1
• /
• pp.69-82
• /
• 1992

The purpose of this study is to analyze the cooker's regnition and real attitude abut standard cost system who are engazing in hotel restaurants in Seoul area. The sample was consisted of 307 cookers(male ; 82.7%, female ; 17.3%_ and the used method in analyzing is surveying method and statistical analysis(SPSS PC Package ; Version 3.0). The results of this study are summarized as follows ; 1. Standard cost system, mass purchase and proper recipe were presented in order to economize on real cost and the purchase and preservation of food were presented as important control factor to econimize cost. 2. Most coolers were recognizing the necessity of standard cost system and they relyed the purpose of standard cost calculation on standard cost control. They also thought standard cost accounting information system as good method to economize cost and they were favorable abut the usage of computer in improving working ability. 3. Most of cookers(80%) wanted to be independant restaurant manager and they were favorable Korean restaurant and Western restaurant. 4. The cookers represented the oder of importance by nutrition, preferance of food, economy in composing cooking menu and by taste, odor, variety, decoration in cooking.

• Nuclear Engineering and Technology
• /
• v.21 no.1
• /
• pp.18-31
• /
• 1989

To analyze the impact of air pollution control on electricity generation cost, a computer program was developed. POGEN calculates levelized discounted power generation cost including additional air pollution control cost for coal power plant. Pollution subprogram calculates total capital and variable costs using governing equations for flue gas control. The costs are used as additional input for levelized discounted power generation cost subprogram. Pollution output for Rue Gas Desulphurization direct cost was verified using published cost data of well experienced industrialized countries. The power generation costs for the year 2001 were estimated by POGEN for three different regulatory scenarios imposed on coal power plant, and by levelized discounted power generation cost subprogram for nuclear power. Because of uncertainty expected in input variables for future plants, sensitivity and uncertainty analysis were made to check the importance and uncertainty propagation of the input variables using Latin Hypercube Sampling and Multiple Least Square method. Most sensitive parameter for levelized discounted power generation cost is discount rate for both nuclear and coal. The control cost for flue gas alone reaches additional 9-11 mills/kWh with standard deviation less than 1.3 mills/kWh. This cost will be nearly 20% of power generation cost and 40% of one GW capacity coal power plant investment cost. With 90% confidence, the generation cost of nuclear power plant will be 32.6-51.9 mills/kWh, and for the coal power plant it will be 45.5-50.5 mills/kWh. Nuclear is favorable with 95% confidence under stringent future regulatory requirement in Korea.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.9 no.4
• /
• pp.25-31
• /
• 2009

In this paper, the implementation of a production control system based on RFID has been studied in order to obtain an exact Cost Center data such as the name of workers included a process of work and a time period to finish the process. The cost center of a worker will be correctly obtained by checking the work time using RFID tag data and by transmitting the data to a server of ERP or POP system. And also warming up time, cleaning time, power failure, and out of order sign will be checked and calculated using the data stored in RFID tags attached in workers and machine facilities. Therefore, exact Cost Center data will be obtained by the production control system with touch screens entering the data according to the situation in real time.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.51 no.11
• /
• pp.503-509
• /
• 2002

In this paper, the robust non-fragile guaranteed cost control problem is studied for a class of linear large-scale systems with uncertainties and a given quadratic cost functions. The uncertainty in the system is assumed to be norm-bounded and time-varying. Also, the state-feedback gains for subsystems of the large-scale system are assumed to have norm-bounded controller gain variations. The problem is to design a state feedback control laws such that the closed-loop system is asymptotically stable and the closed-loop cost function value is not more than a specified upper bound for all admissible uncertainties and controller gain variations. Sufficient conditions for the existence of such controllers are derived based on the linear matrix inequality (LMI) approach combined with the Lyapunov method. A parameterized characterization of the robust non-fragile guaranteed cost controllers is given in terms of the feasible solutions to a certain LMI. A numerical example is given to illustrate the proposed method.