• International Journal of Control, Automation, and Systems
• /
• v.4 no.4
• /
• pp.428-437
• /
• 2006

Many physical systems are hybrid in the sense that they have continuous behaviors and discrete phenomena. In control system with multiple models, switching strategy and stability of the closed-loop system under switching are very important issues. In this paper, a novel adaptive control scheme based on multiple parameter models is proposed to cope with a change in Parameters. Switching strategy guarantees the non-increase in the global control Lyapunov function if the estimation of Lyapunov function value converges. Least-square estimation is used to find the estimated value of the Lyapunov function. Switching and adaptation law guarantees the stability of closed-loop system in the sense of Lyapunov. Simulation results on anti-lock brake system are shown to verify the effectiveness of the proposed controller in view of a large change in system parameters.

• Journal of Korean Institute of Industrial Engineers
• /
• v.26 no.2
• /
• pp.117-127
• /
• 2000

In this paper, we propose a new convex combination weight rule for the cross decomposition method which is known to be one of the most reliable and promising strategies for the large scale optimization problems. It is called generalized cross decomposition, a modification of linear mean value cross decomposition for specially structured linear programming problems. This scheme puts more weights on the recent subproblem solutions other than the average. With this strategy, we are having more room for selecting convex combination weights depending on the problem structure and the convergence behavior, and then, we may choose a rule for either faster convergence for getting quick bounds or more accurate solution. Also, we can improve the slow end-tail behavior by using some combined rules. Also, we provide some computational test results that show the superiority of this strategy to the mean value cross decomposition in computational time and the quality of bounds.

• Proceedings of the KIPE Conference
• /
• 2005.07a
• /
• pp.538-541
• /
• 2005

Most realistic control systems contain nonlinearities of some form. One nonlinearity commonly found in control systems is a saturating element. If integral control is applied to such a system to eliminate steady state error, an undesired side effect known as integrator windup may occur when lage setpoint changes are made. This effect leads to a characteristic step response with a large overshoot and a very high settling time. To avoid this situation, many different anti-windup strategies have been suggested. But existing strategies remain over shoot and high settling time. This paper proposes a new anti-windup strategy for PI speed controllers. When the speed control system is changed P controller to PI controller. Integrator has an appropriate initial value. This value results over shoot and high settling time. The SIMULINK/MATLAB-based comparative simulation results and experiment results of speed controller have shown its superior control performance to that of a proposed anti-windup speed controller.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2014.07a
• /
• pp.99-100
• /
• 2014

Even though many projects of new development and redevelopment for information systems are invested, they are not taken care of from the perspective of administration and evaluation. Also, decision makers fall short of not only support the process to check alternatives and select an alternative for investment and but also provide necessary information so as to maximize the effects of investments. That is to say, the suggestion of general direction toward IT investment is debatable. Against this backdrop, we propose a value measurement model to manage information systems.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2014.07a
• /
• pp.101-102
• /
• 2014

Results of Investment mean not results of procedure but the final goal of an organization. That is to say, results focus on success or failure of investment. So, cost effectiveness means financial cost that is affected in order to attain the output of organizational goal. Many enterprises are investing in developing and redeveloping various projects of information systems. But, it is not generally considered to check values with monitoring and evaluating their projects. We propose a new value model for information systems investment.

• Journal of Electrical Engineering and Technology
• /
• v.4 no.1
• /
• pp.66-78
• /
• 2009

This paper introduces the design of a fuzzy logic controller in conjunction with direct torque control strategy for a Permanent Magnet synchronous machine. A stator flux angle mapping technique is proposed to reduce significantly the size of the rule base to a great extent so that the fuzzy reasoning speed increases. Also, a fuzzy resistance estimator is developed to estimate the change in the stator resistance. The change in the steady state value of stator current for a constant torque and flux reference is used to change the value of stator resistance used by the controller to match the machine resistance.

• Transactions of Materials Processing
• /
• v.12 no.5
• /
• pp.421-432
• /
• 2003

The dies & molds are a very economical production tool and a high value-added product because of its mass production capability compared to other production methods. Due to the very stiff international competitiveness, the industries meet many obstacles. For the promotion of the industry, the status and the international trends of the industry are measured. The vision and strategy are driven. In Korea, large portion of dies and molds are still low value-added and make large number of tools. In order to advance this industry to the high-tech area and gain competitiveness in the global marketplaces, effective means of resource investment and strategy should be properly provided.

• Journal of Ocean Engineering and Technology
• /
• v.37 no.3
• /
• pp.122-128
• /
• 2023

Autonomous berthing is a crucial technology for autonomous ships, requiring optimal trajectory planning to prevent collisions and minimize time and control efforts. This paper presents a two-phase, two-point boundary value problem (TPBVP) strategy for creating an optimal berthing trajectory for a twin-propeller, twin-rudder ship with autonomous berthing capabilities. The process is divided into two phases: the approach and the terminal. Tunnel thruster use is limited during the approach but fully employed during the terminal phase. This strategy permits concurrent optimization of the total trajectory duration, individual phase trajectories, and phase transition time. The efficacy of the proposed method is validated through two simulations. The first explores a scenario with phase transition, and the second generates a trajectory relying solely on the approach phase. The results affirm our algorithm's effectiveness in deciding transition necessity, identifying optimal transition timing, and optimizing the trajectory accordingly. The proposed two-phase TPBVP approach holds significant implications for advancements in autonomous ship navigation, enhancing safety and efficiency in berthing operations.

• International conference on construction engineering and project management
• /
• 2015.10a
• /
• pp.746-747
• /
• 2015

Recently, Korea has achieved accumulated total value of orders of six hundred billion dollars in international construction market, and it is facing a new turning point by entering the overseas construction market. However, according to the statistics on the current internal construction market, the accumulated value of orders has been mainly obtained by plant projects in the Middle-East area. To improve international competitiveness of Korean construction industry, it is required to expand and diversify the target areas and construction business sectors. To expand markets, each construction firm should establish the expansion strategy and assess the capability which includes the strength and weakness of their firm. Therefore, this research aims to evaluate the capability of the Korean construction firms for overseas expansion. Through the research, Korean construction industry is expected to strengthen competitiveness toward the overseas markets. Furthermore, this research contributes to expanding and diversifying markets for domestic construction firms.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.31 no.4
• /
• pp.28-44
• /
• 2023

This study investigates aircraft lessor business models by studying cases and interviewing experts to analyze investors and business strategies of aircraft lessor. The results confirm that there is a wide range of investors including institutional investors, financial institutions, insurance companies, corporations, and wealthy individuals for aircraft lessor. Aircraft lessors can be categorized based on its required rate of return (cost of capital) into bank-investing core, institutional investor-investing value-added, and hedge fund-investing opportunistic. Aircraft lessor decides leasing rate by aircraft purchasing price and lessee's credit rating. Core aircraft lessors invest in new aircrafts for new placement or sale-and-leaseback strategy requiring little technical risk in aircraft, value-added lessors invest in middle-aged aircrafts for re-leasing, opportunistic lessors invest in old aircrafts for freighter conversion or part-out strategy requiring high level of expertise. This study provides insights for future Korean aircraft lessor establishment and investment.