• Korean Journal of Optics and Photonics
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• v.27 no.4
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• pp.133-142
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• 2016

This paper presents the design and simulation of a three-dimensional pixel-by-pixel scanning light detection and ranging (LIDAR) system with a microelectromechanical system (MEMS) scanning mirror and direct sequence optical code division multiple access (DS-OCDMA) techniques. It measures a frame with $848{\times}480$ pixels at a refresh rate of 60 fps. The emitted laser pulse waves of each pixel are coded with DS-OCDMA techniques. The coded laser pulse waves include the pixel's position in the frame, and a checksum. The LIDAR emits the coded laser pulse waves periodically, without idle listening time to receive returning light at the receiver. The MEMS scanning mirror is used to deflect and steer the coded laser pulse waves to a specific target point. When all the pixels in a frame have been processed, the travel time is used by the pixel-by-pixel scanning LIDAR to generate point cloud data as the measured result.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.2
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• pp.124-132
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• 2017

With the growth of interest in the UAVs, the study of the UAV collision avoidance is in progress. Lidar, Video camera, laser sensor, and ultrasonic sensor may be utilized for collision avoidance of UAV. In this paper, the characteristics of MB 1230 ultrasonic sensor is analyzed through the experiment. When concurrently using multitudinous ultrasonic sensors, ultrasonic sensors do not generate correct measurement values. To solve ultrasonic sensor interference, sequentially transmitting ultrasonics signal is suggested by using 'Enable' signal input of ultrasonic sensor, so by activating each ultrasonic sensor gradually. This proposed solution is also verified by experimentation.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1508-1510
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• 2003

비접촉 방식인 광 삼각측량법(optic triangulation method)에 의한 고정도 변위센서를 반도체 레이저 다이오드와 리니어 CCD를 이용하여 구현하였다. 개발한 고유의 알고리듬을 채용하여 측정 분해능 보다 적은 CCD pixel(256 pixel)로 고분해능(2,560분해능, $4{\mu}m$)을 실현함으로써, 결과적으로 저가이며 소형의 고정도 변위센서를 개발하였다. 또 검출물체의 색상이나 재질에 따른 검출특성의 현저한 차이를 보상하기 위하여 LFTC(laser flash time control)과 AGC(auto gain control)을 적용하여 안정된 검출결과를 얻을 수 있었다. 개발된 변위센서의 특성은 다음과 같다. 측정 거리:30mm, 유효측정 범위: -5.09${\sim}$5.10mm, 분해능:4um, 직선성:${\pm}1%$.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.203-204
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• 2008

한의학 진단의 중요 요소인 맥진을 자동화한 맥진기에서뿐만 아니라 비관혈적 심혈관 기능 평가를 위해서 요골동맥 맥파 측정이 널리 활용되고 있다. 요골동맥 맥파는 피험자의 생리적, 병리적 원인을 통제하더라도 가압력이 변함에 따라 형태가 달라지며, 어느 시점 맥파를 피험자의 상태를 대표하는 맥파로 해야 할지에 대한 명확한 기준이 없어 맥압이 최대가 되는 시점의 맥파를 사용하고 있다. 그러나, 맥파가 측정되는 가압력 범위뿐만 아니라 맥압이 최대가 되는 시점이 피험자마다 다르기 때문에 정확한 대표 맥파를 획득하기 위해서는 보다 가압력 단계를 늘려야 하며, 결과적으로 측정시간이 보다 길어지게 될 것이다. 본 논문에서는 최소한의 가압단계로도 보다 정확히 대표 맥파를 획득할 수 있는 방법을 개발할 수 있도록, 정밀 제어가 가능한 가압 로봇 축, 가압에 의해 눌리는 피부이동 거리 측정을 위한 레이저 센서, 가압에 따른 피부 반발력과 맥파를 측정할 수 있는 압력 센서로 구성된 테스트 지그를 개발하였다. 이를 통해 모터 이동 스텝 수에 따른 피부 이동 거리 특성, 피부 이동 거리에 따른 맥파 변화 특성 등을 관찰할 수 있었으며, 향후 효과적인 대표 맥파 획득 방법을 개발할 수 있을 것으로 기대한다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.3
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• pp.263-273
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• 2008

The precision of sensors' position is particularly important in the application of road extraction or digital map generation. In general, the various ranging solution systems such as GPS, Total Station, and Laser Ranger have been employed for the position of the sensor. Basically, the ranging solution system has problems that the signal may be blocked or degraded by various environmental circumstances and has low temporal resolution. To overcome those limitations a IMU/range integrated system could be introduced. In this paper, after pointing out the limitation of extended Kalman filter which has been used for workhorse in navigation and geodetic community, the two sampling based nonlinear filters which are sigma point Kalman filter using nonlinear transformation and carefully chosen sigma points and particle filter using the non-gaussian assumption are implemented and compared with extended Kalman filter in a simulation test. For the ranging solution system, the GPS and Total station was selected and the three levels of IMUs(IMU400C, HG1700, LN100) are chosen for the simulation. For all ranging solution system and IMUs the sampling based nonlinear filter yield improved position result and it is more noticeable that the superiority of nonlinear filter in low temporal resolution such as 5 sec. Therefore, it is recommended to apply non-linear filter to determine the sensor's position with low degree position sensors.

• Journal of Advanced Navigation Technology
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• v.24 no.3
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• pp.192-197
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• 2020

Recently, the technologies related to autonomous drive has studying the goal for safe operation and prevent accidents of vehicles. There is radar and camera technologies has used to detect obstacles in these autonomous vehicle research. Now a day, the method for using LiDAR sensor has considering to detect nearby objects and accurately measure the separation distance in the autonomous navigation. It is calculates the distance by recognizing the time differences between the reflected beams and it allows precise distance measurements. But it also has the disadvantage that the recognition rate of object in the atmospheric environment can be reduced. In this paper, point cloud data by triangular functions and Line Regression model are used to implement measurement algorithm, that has improved detecting objects in real time and reduce the error of measuring separation distances based on improved reliability of raw data from LiDAR sensor. It has verified that the range of object detection errors can be improved by using the Python imaging library.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.34 no.2
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• pp.217-228
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• 2024

LiDAR(Light Detection And Ranging) sensors, which play a pivotal role among cameras, RADAR(RAdio Detection And Ranging), and ultrasonic sensors for the safe operation of autonomous vehicles, can recognize and detect objects in 360 degrees. However, since LiDAR sensors use lasers to measure distance, they are vulnerable to attackers and face various security threats. In this paper, we examine several security threats against LiDAR sensors: relay, spoofing, and replay attacks, analyze the possibility and impact of physical jamming attacks, and analyze the risk these attacks pose to the reliability of autonomous driving systems. Through experiments, we show that jamming attacks can cause errors in the ranging ability of LiDAR sensors. With vehicle-to-vehicle (V2V) communication, multi-sensor fusion under development and LiDAR anomaly data detection, this work aims to provide a basic direction for countermeasures against these threats enhancing the security of autonomous vehicles, and verify the practical applicability and effectiveness of the proposed countermeasures in future research.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.27-29
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• 2004

This paper presents a sensor model design based on Monte Carlo Localization method. First, we define the measurement error of each sample using a map matching method by 2-D laser scanners and a pre-constructed grid-map of the environment. Second, samples are assigned probabilities due to matching errors from the gaussian probability density function considered of the sample's convergence. Simulation using real environment data shows good localization results by the designed sensor model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.683-684
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• 2012

• Composites Research
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• v.31 no.4
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• pp.145-150
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• 2018

Various structural health monitoring (SHM) systems have been suggested for aerospace industry in order to increase its life-cycle and economic efficiency. In the case of aircraft structure madden with metal, a major concern was hot spots, such as notches, bolts holes, and where corrosion or stress concentration occurs due to moisture or salinity. However, with the increasing use of composites in the aerospace industry, further advanced SHM systems have been being required to be applied to composite structures, which have much complex damage mechanism. In this paper, a method of acoustic emission localization for composite structures using Q-switched laser and multiple Amplifier-integrated PZTs have been proposed. The presented technique aims at localization of the AE with an error in distance of less than 10 mm. Acoustic emission simulation and the localization attempt were conducted in the composite structure to validate the suggested method. Localization results, which are coordinates of detected regions, grid plots and color intensity map have been presented together to show reliability of the method.