• 한국정보통신설비학회:학술대회논문집
• /
• 2007.08a
• /
• pp.55-58
• /
• 2007

An adaptive subcarrier allocation scheme based on comparative superiority of opportunity cost between groups is proposed for the enhancement of system capacity and its simple implementation at the base station of a multiuser OFDM system. The proposed algorithm is similar to the blockwise or the decentralized subcarrier allocation algorithm proposed by Xiaowen et al and Alen et al, respectively. In the proposed algorithm, however, all subcarriers are grouped according to the coherence bandwidth and the comparative superiority concept, which swaps the groups between users if the system capacity is increased, is adopted for the enhancement of system capacity. In addition, the proposed algorithm provides a simple solution for the conflict problem among users by reallocating only the conflicted groups and unassigned groups instead of reallocating entire groups. Simulation results demonstrate that the proposed algorithm increases the system capacity effectively over a static, an adaptive blockwise, and a decentralized subcarrier allocation algorithms.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.1
• /
• pp.102-108
• /
• 2008

This paper presents robust and adaptive control method for complicated three dimensional crane systems with uncertain effect. We consider an overhead crane system in which a trolly located on its top is moved to x- and y-axis independently. We first approximate the complicated crane model through linearization approach to simply construct a PD control and then design an adaptive control system for compensating modeling error and control deviation which is feasibly occurred due to system perturbation in practice. An adaptive control scheme is analytically derived using Lyapunov stability theory for a given bound of system perturbation. We accomplish numerical simulation for evaluation of the proposed control system and demonstrate its superiority comparing with the traditional control strategy.

• Journal of Electrical Engineering and Technology
• /
• v.8 no.5
• /
• pp.1040-1048
• /
• 2013

In this paper, a sensorless pitch angle control method for a wind generation system is suggested. One-step-ahead prediction control law is adopted to control the pitch angle of a wind turbine in order for electric output power to track target values. And it is shown that this control scheme using the inverse dynamics of the controlled system enables us to predict current wind speed without an anemometer, to a considerable precision. The inverse input-output of the controlled system is realized by use of an artificial neural network. The proposed control and wind speed prediction method is applied to a Double-Feed Induction Generation system connected to a simple power system through computer simulation to show its effectiveness. The simulation results demonstrate that the suggested method shows better control performances with less control efforts than a conventional Proportional-Integral controller.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.9
• /
• pp.1245-1254
• /
• 2004

In this paper, we deal with a precise position synchronous control of four-axes system which is working under various load disturbances. Each axis driving system is consisted of a speed controller and an acceleration controller as an inner loop instead of conventional current control scheme. The acceleration control plays an important roll to suppress load disturbances quickly. Also, each axis is coupled by a maximum position synchronous error comparison to minimize position synchronous errors according to integration of speed differency. As a result, the proposed system enables precise synchronous control with good robustness against load disturbances during transient as well as steady state. The stability and robustness of the proposed system are investigated through its frequency characteristic and numerical simulations. Finally, experimental results under load disturbances demonstrate the effectiveness of the proposed control system fur four-axes position synchronous control.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.10a
• /
• pp.565-568
• /
• 1995

This paper presents the position control of a closed-loop cylinder system using ER(electro-rheological)valve actuators. Following the field-dependent pressure analysis of the ER valve actuators on the basis of Bingham model of ER fluids, a 3 d.o.f. close-loop sylinder system having the heave, roll and pitch motions is proposed. The governing equations of motion are derived using Lagrange's equation, and a control model is established by considering system uncertain parameters such as load conditions. A sliding mode controller which has inherent robustness to system uncertainties is adopted to achieve robust tracking control performance. Tracking control results for sinusoidal trajectory were presented in order to demonstrate the effectiveness of the proposed control system.

• International Journal of Automotive Technology
• /
• v.8 no.3
• /
• pp.327-335
• /
• 2007

A new optimization scheme and some key techniques are proposed in the development of a vehicle glass drop design software system. The key issues of the design system are how to regenerate the glass surface and make the vehicle glass drop down along the glass channels. To resolve these issues, a parameterized model was created at first, in which the optimizing method and Knowledge Fusion techniques were adopted the optimized process was then written into the glass drop design system by coding with C language and UGS/Open Application Programme Interface functions etc. Therefore, the designer or engineer can simulate the process of glass dropping along the channels to assess the potential interference between glass and door accessory by using this software system. All of the testing results demonstrate the validity of the optimizing scheme, and the parametric design software effectively solves the key issues on development of the door accessory package.

• IE interfaces
• /
• v.5 no.2
• /
• pp.53-74
• /
• 1992

In order to design an FMS(Flexible Manufacturing System), an effective design tool is necessary for selecting and anlayzing the complex interacting factors of a manufacturing system. Considering most of the previous researches have been focused on evaluating the designed FMS, development of an integrated FMS designing system is needed for performing the design task such as machine selection and layout determination as well as the evaluation task of the designed FMS. In this paper, we developed a prototype of such a system called the intelligent FMS designer based on the techniques of Expert System and Simulation. By using this designing system, possible design alternatives can be analyzed and appropriate manufacturing capacity can be estimated at the designing stage. Various operating characteristics of the designed FMS can be also predicted before it is implemented. Eventually a suitable design alternative can be provided with cost details within relatively short time period. To demonstrate the performance and effectiveness of the designer, a simple example is tested. The results show a great potential for automating design processes of an FMS.

• Journal of Computing Science and Engineering
• /
• v.7 no.3
• /
• pp.204-210
• /
• 2013

We present the motivation, design and implementation of a smart home system in Korea. Our system is open, extensible, integrated, intelligent, and usage-centric. We detail the challenges and key design requirements for the smart home system based on our past experiences, and show how convergence system design is a capable methodology for enabling an integrated and multi-faceted home management system that encompasses energy management, home appliance control, environment management, u-health, and living support functionalities under a single unified design. Using energy management as a specific case study, we demonstrate how convergence system design can encapsulate technology heterogeneity and hardware-software disparity without compromising simple yet powerful user interfaces.

• Proceedings of the KIEE Conference
• /
• 1999.11c
• /
• pp.482-484
• /
• 1999

In this paper, we propose a voting method for capacitance measurement. Nowadays the measurement system is changing from analog system to digital system. However, capacitance measurement system has a data error because of the noise. The data of general digital measurement system include an internal and external measurement noises that highly affect to the results. Therefore, this paper proposes data compensation method using voting method. Finally, simulation results are used to demonstrate the efficiency of the proposed method.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2001.04a
• /
• pp.598-601
• /
• 2001

As many sensors and actuators are used in many automated system, various industrial networks are adopted for digital control system. In order to take advantages of the networking, however, the network implementation should be carefully designed to satisfy real-time requirements considering network delays. This paper presents the implementation scheme of a networked control system via Profibus-DP network. More specifically, the effect of the network delay on the control performance was evaluated on a Profibus-DP testbed, and a GA based PID tuning algorithm is proposed to demonstrate the fesibility of the networked control system.