• Journal of the Korean Society of Safety
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• v.31 no.4
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• pp.35-41
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• 2016

In order to guarantee the process safety and prevent accidents, the deviations from normal operating conditions should be monitored and their root causes have to be identified as soon as possible. The statistical theories-based method among various fault diagnosis methods has been gaining popularity, due to simplicity and quickness. However, according to fault magnitudes, the scalar value generated by statistical methods can be changed and this point can lead to produce wrong information. To solve this difficulty, this work employs PCA (Principal Component Analysis) based method with qualitative information. In the case study of our previous study, the number of assumed faults is much smaller than that of process variables. In the case study of this study, the number of predefined faults is 19, while that of process variables is 6. It means that a fault diagnosis becomes more difficult and it is really hard to isolate a single fault with a small number of variables. The PCA model is constructed under normal operation data in order to get a loading vector and the data set of assumed faulty conditions is applied with PCA model. The significant changes on PC (Principal Components) axes are monitored with CUSUM (Cumulative Sum Control Chart) and recorded to make the information, which can be used to identify the types of fault.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.4
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• pp.285-302
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• 2010

Active aeroelastic control is an emerging technology aimed at providing solutions to structural systems that under the action of aerodynamic loads are prone to instability and catastrophic failures, and to oscillations that can yield structural failure by fatigue. The purpose of the aeroelastic control among others is to alleviate and even suppress the vibrations appearing in the flight vehicle subcritical flight regimes, to expand its flight envelope by increasing the flutter speed, and to enhance the post-flutter behavior usually characterized by the presence of limit cycle oscillations. Recently adaptive and robust control strategies have demonstrated their superiority to classical feedback strategies. This review paper discusses the latest development on the topic by the authors. First, the available control techniques with focus on adaptive control schemes are reviewed, then the attention is focused on the advanced single-input and multi-input multi-output adaptive feedback control strategies developed for lifting surfaces operating at subsonic and supersonic flight speeds. A number of concepts involving various adaptive control methodologies, as well as results obtained with such controls are presented. Emphasis is placed on theoretical and numerical results obtained with the various control strategies.

• Transactions on Control, Automation and Systems Engineering
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• v.3 no.3
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• pp.181-189
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• 2001

The software components of embedded control systems get extremely complex as they are designed into distributed systems get extremely complex as they are designed into distributed systems consisting of a large number of inexpensive microcontrollers interconnected by low-bandwidth real-time networks such as the controller area network (CAN). While recently emerging middleware technologies such as CORBA and DCOM address the complexity of distributed programming, they cannot be directly applied to distributed control system design due to their excessive resource demand and inadequate communication models. In this paper, we propose a CORBA-based middleware design for CAN-based distributed embedded control systems. Our design goal is to minimize its resource need and make it support group communication without losing the IDL (interface definition language) level compliance to the OMG standards. To achieve this, we develop a transport protocol on the CAN and a group communication scheme based on the well-known publisher/subscriber model. The protocol effectively realizes subject-based addressing and supports anonymous publisher/subscriber communication. We also customize the method invocation and message passing protocol, referred to as the general inter-ORB protocol (GIOP), of CORBA so that CORBA method invocations are efficiently serviced on a low-bandwidth network such as the CAN. This customization includes packed data encoding and variable-length integer encoding for compact representation of IDL data types. We have implemented our CORBA-based middleware on the mArx real-time operating system we have developed at Seoul National University. Our experiments clearly demonstrate that it is feasible to use CORBA in developing distributed embedded control systems possessing severe resource limitations. Our design clearly demonstrates that it is feasible to use a CORBA-based middleware in developing distributed embedded systems on real-time networks possessing severe resource limitations.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.573-577
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• 2009

Dynamic behavior simulation of supersonic engine was performed and PI control algorithm was studied for the buzz control in the inlet and the thrust control. Firstly, required thrust was tracked according to the fuel flow control and then inlet pressure was regulated through the nozzle throat area control so that the buzz margin has the positive all the time. The control was performed according to the change of flight Mach number, altitude and angle of attack. The proportional gain and the integral gain for regulating the buzz margin was induced and simulated. In the results, it was confirmed and satisfied that control target in the operating area was changed the angle of attack from $0^{\circ}$ to $10^{\circ}$ at the flight Mach number of 2.1~3.0.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.2
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• pp.27-34
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• 2014

Buzz margin scheduling and control technique which are suitable to regulate stable and high pressure air in wide range of Mach number are suggested for fixed geometry of a supersonic intake. From the analysis of preceding study, most effective control variable is induced and scheduling law is newly suggested in a real application point of view. The appropriateness of the control law in wide range of Mach number is addressed by numerical simulation of controlled propulsion system. Also, the simulation for stabilization and tracking performances of the controller are studied to investigate the phenomena under flight maneuver and disturbances.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.6
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• pp.419-429
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• 2020

In conducting a mission to explore and track targets using a number of unmanned aerial vehicles(UAVs), performance for that mission may vary significantly depending on the operating conditions of the UAVs such as the number of operations, the altitude, and what future flight paths each aircraft decides based on its current position. However, studies on the number of operations, operating conditions, and flight patterns of unmanned aircraft in these surveillance missions are insufficient. In this study, several types of flight simulations were conducted to detect and determine targets while multiple UAVs were involved in the avoidance of collisions according to various autonomous flight algorithms based by flocking theory, and the results were presented to suggest a more efficient/effective way to control a number of UAVs in target detection missions.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.5
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• pp.92-99
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• 2008

This paper describes an signal processing method for the hall sensorless position control of ETC control system using a BLDC motor. The proposed ETC control system, which is mainly consisted of a BLDC motor, a throttle plate, a return spring and reduction gear, has a position sensor with an analog voltage output on the throttle valve instead of BLDC motor for detecting rotor position of motor. So the additional commutation information is necessarily needed to control the mentioned ETC module. In order to estimate and determine the commutation state, it is proposed to properly manipulate the resolution of A/D converter considering the mechanical parameter, that is, the number of motor slot and the ratio of reduction gear. Through this method, the estimation of commutation state for operating the system is possible and the discrete signal for commutation is stably obtained. The validity of the method is examined through the experimental results.

• Korean Journal of Adult Nursing
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• v.20 no.2
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• pp.353-363
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• 2008

Purpose: This study was conducted to develop a timeout protocol as the process of patients verification in the operating room, and to evaluate its effects. Methods: The timeout protocol was developed based on the experience of practices and the universal protocol of JCAHO 2004. The subjects of this study were 192 surgical members working in the operating room at an university hospital in Daegu, Korea. Results: The timeout protocol was developed in six steps; participants verification, encouragement of compliance, verification of right 3 PSP, agreement of surgical team members, verification of the parties to a patient, patient agreement. The data which have been resulted from the experimental group show significantly higher than those of control group as follows; cognition(t = -6.580, p = .000), contents of performance; progress of anesthesiologist as leader(${\chi}^2$ = 29.029, p = .000), verification of right patient, right site and right procedure(${\chi}^2$ = 40.663, p = .000), participation of surgical team(${\chi}^2$ = 68.412, p = .000), and the number of cases of performance(${\chi}^2$ = 242.900, p = .000). Conclusion: It suggests that medical accidents caused by failures in a preoperative verification process can be prevented if a timeout is conducted active involvement and effective communication among surgical team members for a final verification of the correct patient, procedure, and site.

• Journal of the Semiconductor & Display Technology
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• v.21 no.1
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• pp.50-55
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• 2022

Due to the wavelength shift problem of micro LED caused by the change of current density, the active matrix driving pixel circuit that is used in OLED cannot be applied to micro LED displays. Therefore, we need a gray scale method based on modulation of duration time of light emission. In this study, we propose the PWM-controlled micro LED pixel circuit based on CMOS thin film transistors (TFTs). By adopting CMOS inverter structure, we can reduce the number of storage capacitors from the circuit and make the operating speed of the circuit faster. Most of all, our circuit is designed to make operating speed of PWM circuit faster by adopting feedback effect through double gate TFT structure. As a result, it takes about 4.7ns to turn on the LED and about 5.6ns to turn it off. This operating time is short enough to avoid the color distortion and help the precise control of the gray scale.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.5
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• pp.429-433
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• 2007

A number of techniques have been developed for estimation of speed or position in motor drives. The accuracy of these techniques is affected by the variation of motor parameters such as the stator resistance, stator inductance or torque constant. This paper is proposed a neural network based estimator for torque and ststor resistance in IPMSM Drives. The neural weights are initially chosen randomly and a model reference algorithm adjusts those weights to give the optimum estimations. The neural network estimator is able to track the varying parameters quite accurately at different speeds with consistent performance. The neural network parameter estimator has been applied to slot and flux linkage torque ripple minimization of the IPMSM. The validity of the proposed parameter estimator is confirmed by the operating characteristics controlled by neural networks control.