• 한국자동차공학회논문집
• /
• 제19권3호
• /
• pp.113-121
• /
• 2011

Rollover accident is one of the serious traffic accident and rollover accident takes high portion of all accident. The most common type of rollover is a tripped rollover which occupy 95% of all type of single-vehicle rollover. Tripped rollover occurs when a vehicle leaves normal road way and tripped by loose gravel, soil of fixed object such as guard rail, curbs and ditches. And the rest of the type of rollover is un-tripped rollover. An un-tripped rollovers that occurs during high-speed collision avoidance maneuvers. In this paper, presents the explanation of the un-tripped rollover test method and procedure, additionally this paper deals with various occurrence in the un-tripped test such as occurring excessive tire camber in the un-tripped test, tire side-wall contact with road surface and roll oscillation. And this paper analyzes the analysis of the roll rate amplitude in specific frequency through the FFT (Fast Fourier Transform) and the roll angle at the steering reverse timing which is the Fishhook test roll rate feedback time. Finally, this paper analyzes the relations between the estimated steady state roll gain and rollover stability.

• ETRI Journal
• /
• 제44권4호
• /
• pp.543-559
• /
• 2022

To determine a suitable waveform for Internet of Things (IoT) transmission over low-Earth orbit (LEO) satellites, this paper reports the results of a performance comparison between chirp spread spectrum (CSS)-based LoRa and direct sequence spread spectrum (DSSS)-based Ingenu. The performance of both waveforms was measured in terms of the packet error rate, throughput, and packet loss rate, considering the Doppler effect caused by the high speed of LEO satellites and the interference among multiple terminals. Simulation results indicate that the DSSS scheme is more suitable than the CSS scheme for high-traffic IoT services because of its robustness against interference among multiple terminals. However, the CSS scheme is more suitable than the DSSS scheme for high-mobility IoT services because of its robustness against the Doppler effect. We discuss various solutions, such as the preprocessing of Doppler effect and avoidance of packet collision, to enhance the performance of the DSSS and CSS schemes. The simulation results of the proposed solution show that the enhanced DSSS scheme can be a proper waveform in IoT transmission over LEO satellites for both the high-traffic and high-mobility services.

• 전자공학회논문지CI
• /
• 제39권2호
• /
• pp.21-34
• /
• 2002

구조화된 환경에서 사용되어 지는 일반적인 이동 로봇과 달리 시각장애인을 위한 이동 로봇은 다양한 종류의 이동 장애물들을 고려하도록 설계되어야 한다. 그런데, 이동 장애물, 즉 보행자의 대부분은 어떤 의도를 가지고 이동하게 되므로 로봇이 그 의도를 미리 파악하면서 주행한다면 로봇은 지능적인 주행을 할 수가 있다. 본 논문에서는 격자형 맵을 이용하여 장애물의 의도를 추론하는 방법을 제안하다. 먼저 퍼지 논리와 초음파 센서를 이용하여 주위 환경을 격자형 맵으로 표현하고, 격자형 맵의 CLA(Centroid of Largest Area)점을 이용한 장애물 감지 방법 및 장애물 의도 추론 방법을 제안한다. 제안된 방법의 유용성을 확인하기 위해 실험이 수행되었다.

• 수산해양기술연구
• /
• 제51권2호
• /
• pp.245-256
• /
• 2015

This study is intended to provide navigator with specific information necessary to assist the avoidance of collision and the operation of ships to evaluate the maneuverability of dead weight tonnage 8,000 tons Oil/Chemical tanker. The actual maneuvering characteristics of ship can be adequately judged from the results of typical ship trials. Author carried out sea trials based full scale for turning test in ballast condition and full load condition, semi balanced rudder and flap rudder. The turning circle maneuvering were performed on the starboard and port sides with $35^{\circ}$ rudder angle at the normal continuous rating. The results from tests could be compared directly with the standards of maneuverability of IMO and consequently the maneuvering qualities of the ship is full satisfied with its.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• 제14권4호
• /
• pp.288-294
• /
• 2014

Understanding a ship's present position has been one of the most important tasks during a ship's voyage, in both ancient and modern times. Particularly, a ship's dead reckoning (DR) has been used for predicting traffic situations and collision avoidance actions. However, the current system that uses the traditional method of calculating DR employs the received position and speed data only. Therefore, it is not applicable for predicting navigation within the harbor limits, owing to the frequent changes in the ship's course and speed in this region. In this study, planned routes were applied for improving the reliability of the proposed system and predicting the traffic patterns in advance. The proposed method of determining the dead reckoning position (DRP) uses not only the ships' received data but also the navigational patterns and tracking data in harbor limits. The Mercator sailing formulas were used for calculating the ships' DRPs and planned routes. The data on the traffic patterns were collected from the automatic identification system and analyzed using MATLAB. Two randomly chosen ships were analyzed for simulating their tracks and comparing the DR method during the timeframes of the ships' movement. The proposed method of calculating DR, combined with the information on planned routes and DRPs, is expected to contribute towards improving the decision-making abilities of operators.

• 제어로봇시스템학회논문지
• /
• 제19권5호
• /
• pp.442-449
• /
• 2013

In this paper, a simulation system based on X-Plane and MATLAB/Simulink for multiple UAVs is presented. For the conceptual design of this proposed system, a hierarchical system architecture for multiple UAVs is presented. This architecture has object-oriented data structure which consists of three objects (UAV status, mission and task, and environment) and a hierarchy consisting of four layers (decision making layer, task assignment layer, path and motion planning layer, and collision avoidance layer) is also proposed. In addition, this paper shows a implementation of simulation system based on the proposed system architecture using X-Plane and MATLAB/Simulink. The result of simulation from the developed system in this paper validate capability of application for multiple UAVs in real environment.

• 제어로봇시스템학회논문지
• /
• 제21권9호
• /
• pp.818-826
• /
• 2015

This paper presents a novel methodology for estimating vehicle ego-motion, i.e. tri-axis linear velocities and angular velocities by using stereo vision sensor and 2G1Y sensor (longitudinal acceleration, lateral acceleration, and yaw rate). The estimated ego-motion information can be utilized to predict future ego-path and improve the accuracy of 3D coordinate of obstacle by compensating for disturbance from vehicle movement representatively for collision avoidance system. For the purpose of incorporating vehicle dynamic characteristics into ego-motion estimation, the state evolution model of Kalman filter has been augmented with lateral vehicle dynamics and the vanishing point estimation has been also taken into account because the optical flow radiates from a vanishing point which might be varied due to vehicle pitch motion. Experimental results based on real-world data have shown the effectiveness of the proposed methodology in view of accuracy.

• 한국통신학회논문지
• /
• 제25권1B호
• /
• pp.62-70
• /
• 2000

본 논문에서는 지능형 차량에서 사용되는 레이더 센서 사이의 상호 간섭 억제 방법을 제안한다. 이 연구는 표준화된 펄스형 레이더에서 동기형 간섭 신호의 억제 방안에 관한 것이다. 레이더 펄스의 방사는 ON-OFF 제어되며, OFF 구간에서 수신된 간섭 신호는 각 레이진 별로 분석되어 저장되며 이를 이용하여 ON 구간에서의 거짓 반사파의 위치를 예측하며, 이로써 ON 구간에서의 동기형 간섭 신호를 제거한다. I-Q 변복조 방식의 레이더 시스템에서, Rayleigh 분포와 Rician 분포의 잡음에서의 오경보 확률과 미탐지 확률을 유도하였다. 펄스 신호 유무의 판별 시의 임계값을 적응적으로 조절함으로써 오경보 확률은 감소시키고 미탐지 확률의 저하를 억제하는 방법을 제시하였으며, 시뮬레이션 결과 오경보 확률은 최고 10\sup 4\배 감소하였고 미탐지 확률의 저하는 무시할 정도였다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권5호
• /
• pp.2499-2522
• /
• 2017

Multi-hop networks are a low-setup-cost solution for enlarging an area of network coverage through multi-hop routing. Carrier sense multiple access with collision avoidance (CSMA/CA) is frequently used in multi-hop networks. Multi-hop networks face multiple problems, such as a rise in contention for the medium, and packet loss under heavy-load, saturated conditions, which consumes more bandwidth due to re-transmissions. The number of re-transmissions carried out in a multi-hop network plays a major role in the achievable quality of service (QoS). This paper presents a statistical, analytical model for the end-to-end delay of contention-based medium access control (MAC) strategies. These strategies schedule a packet before performing the back-off contention for both differentiated heterogeneous data and homogeneous data under saturation conditions. The analytical model is an application of Markov chain theory and queuing theory. The M/M/1 model is used to derive access queue waiting times, and an absorbing Markov chain is used to determine the expected number of re-transmissions in a multi-hop scenario. This is then used to calculate the expected end-to-end delay. The prediction by the proposed model is compared to the simulation results, and shows close correlation for the different test cases with different arrival rates.

• 한국지능시스템학회논문지
• /
• 제14권3호
• /
• pp.304-309
• /
• 2004

본 논문에서는 편리한 방식으로 착용할 수 있으며 지능을 지니고 있는 시스템을 구현하고자 한다. 인간을 보조하는 역할을 수행함과 동시에 착용할 수 있는 장점을 지닌 시스템의 구현은 다양한 제어기에 적용될 수 있다. 이동 중인 로봇의 상태를 파악하고 인간을 대신하여 명령을 전달해주는 시스템의 구현이 가능해진 것이다. 본 논문에서는 이동 로봇의 주행 정보를 받아들여 충돌 회피 주행에 필요한 속도와 회전각을 판단하여 명령을 전달하는 시스템을 착용 형태의 장치를 이용하여 구현하였다. 웨어러블 장치의 지능을 구현하기 위해 계층적 퍼지 논리와 신경망의 학습 능력을 결합하였다.