• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.5
• /
• pp.473-482
• /
• 2015

Recent development in science and technology has enabled vehicles to be equipped with advanced autonomous functions. ADAS (Advanced Driver Assistance Systems) are examples of such advanced autonomous systems added. Advanced systems have several operational modes and it has been observed that drivers could be unaware of the mode they are in during vehicle operation, which can be a contributing factor of traffic accidents. In this study, possible mode confusions in a simulated environment when vehicles are equipped with an adaptive cruise control system were investigated. The mental model of the system was designed and verified using the formal analysis method. Then, the user interface was designed on the basis of those of the current cruise control systems. A set of human-in-loop experiments was conducted to observe possible mode confusions and redesign the user interface to reduce them. In conclusion, the clarity and transparency of the user interface was proved to be as important as the correctness and compactness of the mental model when reducing mode confusions.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.6
• /
• pp.596-604
• /
• 2010

In order to investigate the operating conditions and major design parameters of a dual ramjet propulsion system, an theoretical analysis of ramjet and scramjet propulsion systems was performed. The performance characteristics of each engine are delivered by thermo-dynamical cycle analysis, considering loss effects in a real engine. The performance sensitivity analysis is conducted by investigating various performance parameters, such as an intake efficiency, combustor inlet Mach number, configuration of the combustor, fuel flow rate, and exhaust nozzle efficiency. Based on these analysis results, the processes of application to dual ramjet cycle engines are specified.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2021.05a
• /
• pp.104-107
• /
• 2021

전 세계적으로 건조한 지역이 늘어남에 따라 산불 발생 빈도가 증가하고 있다. 이에 대한 대안으로 센서를 이용한 산불 감지 시스템의 연구가 이루어지고 있다. 기존의 서버가 센서의 작동시간 설정값을 보내는 방식은 산불 발생 빈도가 높은 환경에서는 산불 감지가 늦어지고 산불 발생 빈도가 낮은 환경에서는 불필요한 산불 감지로 센서의 생명주기 낮아지는 비효율적인 면이 있다. 이에 본 논문에서는 센서 기반 산불 감지 시스템을 위한 향상된 센싱 주기 기법을 제안한다. 제안하는 센싱 주기 기법은 환경 요인, 센서의 작동시간 알고리즘을 이용하여 환경에 맞는 센서의 작동시간 설정값을 결정한다. 그 후 센서의 화재 감지 알고리즘을 통해 센서는 서버로부터 설정값을 받아 운용모드로 전환하여 화재상황이 났을 시에 서버로 메세지를 보낸 후 생명주기를 위해 저전력모드로 전환한다. 성능평가를 통해 기존의 방식보다 평균 18.1분 빠르게 화재상황을 감지할 수 있고 소모전력도 2.2mA만큼 낮았다. 향우 실제 화재환경에서의 성능평가가 필요하다.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.6
• /
• pp.1371-1381
• /
• 1995

A novel hybrid control scheme to actively control the endpoint position of a very flexible single-link manipulator is proposed. The control scheme consists of a motor mounted at the beam hub and a piezofilm actuator bonded to the surface of the flexible link. The control torque of the motor to produce a desired motion is firstly determined by employing the sliding mode control theory on the equation of motion of the rigid link having the same mass as that of the proposed flexible link. The torque is then applied to the flexible manipulator in order to activate the commanded motion. During the motion, undesirable oscillation is actively suppressed by applying a feedback control voltage to the piezofilm actuator. Consequently, the imposed desired position is accomplished. In order to demonstrate high control performances accrued from the proposed method, computer simulations are undertaken by treating both regulating and tracking control problems.

• Proceedings of the Korean Reliability Society Conference
• /
• 2002.06a
• /
• pp.113-113
• /
• 2002

차량용 Alternator는 기계적인 에너지인 엔진의 회전력을 이용하여 발전을 하여 차량의 전기장치를 작동시키는 데 필요한 전원을 공급하며, Battery에 전원을 충전하는 장치이다. 따라서 Alternator의 고장이 발생하면 초기에는 Battery 전원에 의해서 차량의 제어 및 동작이 가능하나 Battery가 방전되면 차량의 제어는 물론 장비의 작동 자체가 불가능해진다. 차량용 Alternator는 농기계 및 승용차용으로 사용하는 12V Alternator와 상용차 및 특수차량용으로 사용하는 24V Alternator로 나누어진다. 특히 굴삭기는 험지에서의 굴착작업, Breaker 작업 등 진동, 내열, 먼지 등 환경조건이 기존의 차량과는 대조가 되지 않을 정도로 열악하여 일반차량용에서 보다 부품수명도 짧고, 고장발생 모드도 다양하다. 본 장에서는 굴삭기에 사용되는 24V Alternator의 고장모드를 분석하고 Field에서 발생하는 고장을 개선함으로써 MTTF를 향상시키는 방법에 대하여 고찰하고자 한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.9 no.3
• /
• pp.201-207
• /
• 2009

As the existing backdoor worked at user mode, which is application mode, it was possible to check the existence of backdoor by the integrity check of system file. However, for the backdoor using kernel module, it is impossible to check its existence by the integrity check of system file. Even various programs were presented to protect this LKM Kernel backdoor, there is limitation in protection as they examine the changes on the system Call Table. This study, recognizing the danger of invasion through such LKM Kernel backdoor, will provide alternative for the limitation which the existing integrity check couldn't prevent intrusion through Kernel backdoor.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.49 no.7
• /
• pp.6-11
• /
• 2012

A mobile station(MS) in an 802.16e network manages its limited energy using the sleep mode operation. An MS can power down its physical operation components during the unavailability interval of the sleep mode. To reduce energy consumption by increasing the unavailability interval, this paper proposes an enhanced power saving mechanism(ePSM) when both activated Type I and Type II power saving classes(PSCs) exist in an MS. A performance evaluation confirms that ePSM results in the improved performance in terms of the unavailability interval as well as the energy consumption than conventional schemes.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.17 no.7 s.124
• /
• pp.617-623
• /
• 2007

This paper presents an active vibration control of a dynamic system using hybrid mount which consists of elastic rubber-piezostack actuator and elastic rubber-electromagnetic actuator, respectively. After identifying stiffness, damping properties of the elastic rubber, PZT actuator and electromagnetic element, a mathematical model of the hybrid mount is established. The mount model is then incorporated into the dynamic system and the governing equation of motion is obtained in a state space. A sliding mode controller is designed in order to actively attenuate the vibration of the system. Control responses such as acceleration and transmitted force of the dynamic system are experimentally evaluated and presented in time and frequency domains.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.1131-1136
• /
• 2007

This paper presents an active vibration control of a 1-DOF system using hybrid mount which consists of elastic rubber and PZT(piezostack) actuator and elastic rubber and electromagnetic actuator, respectively After identifying stiffness, damping properties of the elastic rubber, PZT actuator and electromagnetic element, a mathematical model of the hybrid mount is established. The mount model is then incorporated into the 1-DOF system and the governing equation of motion is obtained in a state space. A sliding mode controller is designed in order to actively attenuate the vibration of the system. Control responses such as acceleration and transmitted force of the 1-DOF system are experimentally evaluated and presented in time and frequency domains.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2002.04a
• /
• pp.4-5
• /
• 2002

로켓 엔진의 개발에 있어 성능과 수명(life time)에 가장 문제가 되는 것은 연소 안정성에 있다. 일반적으로 연소 불안정을 야기시키는 것은 3가지로서 축방향(longitudinal), 반경방향(radial)과 접선방향(longitudinal) 모드(mode)가 있다. 이와 같은 모드를 제어하는 방법에는 수동적 제어방법으로 음향공(acoustic cavity)과 배플(baffle)이 있으며, 음향공은 모드에 관계없이 특정한 주파수에 맞추어 체적을 조절하여 음향파(acoustic wave)를 감쇄시키는 것이고 배플은 주파수에 관계없이 접선방향 모드를 제어하는 것이 기본 목적이나 허브(hub)를 설치하여 반경방향 모드까지 제어할 수 있다. 음향공은 엔진의 성능 또는 연소장에는 영향을 주지 않고 작동하는 반면, 배플은 초기 엔진설계를 할 때 고려하지 않으면 후에 배플을 장착하였을 때는 초기 설계의 제한 때문에 장착의 어려움과 성능 및 연소장에 영향을 미쳐 원하지 않는 엔진의 시험 결과를 야기할 수 있다. 본 연구에서는 KSR-III와 동일한 조건의 연소기에서 다양한 배플을 장착하였을 경우에 대하여 성능과 연소장에 대하여 예측하였다.