Area Detection Based on Physical Properties of Ultrasound Wave

본 논문은 단일 초음파 센서를 이용하여 직각 주차를 위한 자동차의 주차 보조 시스템에서 주차 공간을 감지하는 방법을 연구의 주제로 삼고 있다. 현재 초음파 센서는 자동차에서 장애물 감지나 평행 주차를 위한 주차 보조 시스템의 공간 감지 시스템에 널리 사용되고 있다. 평행 주차를 위한 공간 감지 시스템에서는 이미 단일 초음파 센서로 공간 감지를 하는 제품이 상용화 되어있으나 직각 주차는 평행주차와는 감지해야 되는 대상의 종류가 더 다양하고 형상의 차이가 더 커진다. 그렇기 때문에 기존에 적용하던 방식을 직각 주차의 공간 감지에 바로 사용하는 것은 무리가 따르게 된다. 본 논문에서는 직각 주차의 공간 감지를 단일 초음파 센서로 감지해내는 방법을 고안해내기 위해, 시뮬레이션과 실제 센서를 이용한 응답으로부터 공간 감지에 적용할 수 있을만한 요소들을 찾아 그에 대해 고찰하였다. 이 과정에서 최종적으로 가장 유용한 방법으로서 초음파 센서가 받아들이는 첫 번째 반사파 근처에서 정해진 역치(threshold)를 넘는 신호가 존재하는 구간의 폭을 측정하고 이 값이 특정 수준 이상으로 유지되는 구간을 장애물의 폭으로서 추정하는 방법을 제안하였고, 다른 종류의 장애물들에 대해 초음파 센서를 이용한 측정 실험을 진행하여 여기서 측정된 결과를 이용하여 이 방법의 성능을 검증하였고, 기존에 사용되던 초음파 센서를 이용한 공간 감지 방법과 성능을 비교하였다. 본 논문에서 제안하는 방법은 사용되는 초음파 센서의 수를 최소화하고 단순한 연산으로 공간을 감지할 수 있기 때문에 실제 주차 보조 시스템을 설계할 때, 적은 비용으로 시스템을 설계하는 데 공헌할 수 있을 것으로 보인다.This paper introduces a parking area detection algorithm for the reverse parking assistant system using a single ultrasonic sensor. An ultrasonic sensor is widely used for the parallel parking assistant system. However, area detection algorithm for parallel parking assistant system cannot be applied to reverse parking assistant system because the errors become much larger due to the presence of a wide range of different types of objects Moreover, some of the front parts of cars have more complex shapes that impede the application of other signal properties for detection. The proposed method determines the parking area based on the measurement of the Signal duration of the first reflected wave including partial multi-path echoes. The results of experiments in a real parking environment show that detection errors are decreased compared to those of the conventional method. In addition, the proposed method does not require large computation power. Because of these features of the proposed method, the parking area detection system can be manufactured at low cost.Docto

열악한 GNSS 신호환경에 대비하는 다중센서 및 협력기반 차량 항법시스템

학위논문(석사) - 한국과학기술원 : 조천식녹색교통대학원, 2016.8 ,[v, 74 p. :]Vehicular application technologies, i.e., autonomous driving cars, have rapidly developed in recent years, as they provide convenience, location-related information, and safety to transportation users. Specially, vehicular navigation technology which provides precise positioning has become a vital component in most transportation systems and, with recent developments, now uses a Global Navigation Satellite System (GNSS). GNSS performance degradations can have various sources, but disconnections of the GNSS signal during signal outages (i.e., tunnels) and non-line-of-sight (NLOS) GNSS signals in urban environments (i.e., urban canyons) lead to significant errors. A number of studies have been conducted with regard to precise positioning methods, but they require a heavy computation cost, show low performance, or have high implementation costs to realize a viable vehicular navigation system. Therefore, in this thesis, two navigation systems which are robust against harsh signal environments and which outperform conventional navigation systems are introduced for vehicles. One of the navigation systems is a sensor-fusion-based navigation system of the type slated for use on Korean next-generation high-speed trains. It is modified to make it feasible for an actual train environment and its outperformance is demonstrated in a comparison to conventional navigation systems with empirical data. Moreover, we develop a non-line-of-sight (NLOS) GNSS signal-detection algorithm and propose cooperative navigation techniques that significantly enhance accuracy and multipath-robustness in urban environments. We discuss the theoretical derivation and realization of the proposed techniques and demonstrate their performance capabilities with numerous Monte Carlo simulations using field measurements with multipath delays. The proposed techniques significantly improve the positioning accuracy of all vehicles and outperform the conventional cooperative positioning technique in urban multipath environments.한국과학기술원 :조천식녹색교통대학원

Feasibility Evaluation for Remediation of Groundwater Contaminated with Heavy Metal using Calcium Polysulfide in Homogeneous media

In this study, column tests using relatively uniform Jumunjin sand media were conducted to evaluate the feasibility ofcalcium polysulfide (CaSx, CPS) in removing high concentration of Zn2+ in groundwater. The injected CPS solutionreacted rapidly with Zn2+ in artificial groundwater and effectively reduced Zn2+ by more than 99% through metal sulfideprecipitation. Since the density (d = 1.27 g/cm3) of CPS solution was greater than that of water, CPS solution settled downrapidly while capturing Zn2+ and formed stable CPS layer similar to dense nonaqueous phase liquid. Mass balance analysison Zn2+ in CPS solution suggested that CPS solution effectively reacted with Zn2+ to form metal sulfide precipitates exceptfor high groundwater seepage velocity of 400 cm/d. With greater groundwater seepage velocity, injected CPS did notcompletely dissolve at the CPS-water interface, but a partially-misible CPS layer continuously moved and reacted withZn2+ in the direction of groundwater flow. Since hydraulic conductivity (Kh) decreased slightly due to the generated metalprecipitates in the inter-pores of media, injection of CPS solution should be optimized to prevent clogging. As evidencedby both XRF and SEM/EDS results, ZnS precipitates were clearly observed through the reaction between the CPSsolution and Zn2+. Further study is warranted to evaluate the feasibility of CPS to remove high-concentration heavy metalcontaminatedgroundwater in complex and heterogeneous media.N