RAIM algorithm considering simultaneous multiple ramp failures

Yun, Ho,Han, Deokhwa,Kee, Changdon,Lee, Jiyun,Heo, Moon Beom Emerald Group Publishing Limited 2015 Aircraft engineering and aerospace technology Vol.87 No.4

<P><B>Purpose</B></P> <P> – The purpose of this paper is to develop and analyze a new multiple hypothesis receiver autonomous integrity monitoring (RAIM) algorithm, which can handle simultaneous multiple ramp failures. </P> <P><B>Design/methodology/approach</B></P> <P> – The proposed algorithm uses measurement residuals and satellite observation matrices of several consecutive epochs for failure detection and exclusion. It detects failures by monitoring the error vector rather than a projection of the error vector. The algorithm assumes that magnitude of range errors can vary with time, while the conventional sequential multiple hypothesis RAIM algorithm assumes that range errors are constant biases. </P> <P><B>Findings</B></P> <P> – The algorithm can detect any instance of multiple failures, including failures that cannot be detected by the conventional RAIM algorithm. It can detect multiple failures with magnitudes of several tens of meters, even though the algorithm must solve an ill-conditioned problem. And it can also deal with ramp failures which cannot be detected by conventional sequential multiple hypothesis RAIM algorithm. The detection capability of the proposed algorithm is not dependent on satellite geometry or types of errors. </P> <P><B>Practical implications</B></P> <P> – Implications for the development of the RAIM algorithm for aviation users are included. In particular, it can be a candidate for a future standard architecture in multiple constellations, multiple frequency and satellite-based augmentation system users. </P> <P><B>Originality/value</B></P> <P> – A new multiple hypothesis RAIM algorithm with a relative RAIM concept is proposed. Also presented is a detailed explanation of the algorithms, including rigorous mathematical expressions, and an analysis of differences in detection capability between the conventional multiple hypothesis RAIM algorithm and proposed algorithm.</P>

Multiple-hypothesis RAIM algorithm with an RRAIM concept

Yun, Ho,Kee, Changdon Emerald Group Publishing Limited 2013 Aircraft engineering and aerospace technology Vol.86 No.1

<B>Purpose</B> - This paper aims to develop and analyse a new multiple-hypothesis receiver autonomous integrity monitoring (RAIM) algorithm. The proposed algorithm can handle simultaneous multiple failures as well as a single failure. <B>Design/methodology/approach</B> - The proposed algorithm uses measurement residuals and satellite observation matrices of several consecutive epochs for failure detection and exclusion. It detects failures by monitoring the error vector itself instead of monitoring the projection of the error vector. The algorithm reduces the minimum detectable bias via the relative receiver autonomous integrity monitoring (RRAIM) scheme. <B>Findings</B> - The algorithm is able to detect any instance of multiple failures, including failures that are not detected by the conventional RAIM algorithm. It is able to detect multiple failures with magnitudes of several tens of meters, although the algorithm has to solve an ill-conditioning problem. The detection capability of the proposed algorithm is not dependent on satellite geometry. <B>Research limitations/implications</B> - The algorithm assumes that the error vectors in three consecutive epochs have biases of similar magnitude. As a result, although the algorithm detects occurrences of drifting error, it cannot identify which measurement(s) has the critical error. <B>Practical implications</B> - The paper includes implications for the development of the RAIM algorithm for aviation users. Especially, it can be a candidate for future standard architecture in multiple constellations, multiple frequency satellite-based augmentation system (SBAS) users. <B>Originality/value</B> - The paper proposes a new multiple-hypothesis RAIM algorithm with an RRAIM concept. A detailed explanation of the algorithms, including rigorous mathematical expressions, is presented. The paper also includes an analysis of differences in detection capability between conventional algorithm and the proposed algorithm depending on satellite geometry.

Korean Wide Area Differential Global Positioning System Development Status and Preliminary Test Results

Yun, Ho,Kee, Chang-Don,Kim, Do-Yoon The Korean Society for Aeronautical and Space Scie 2011 International Journal of Aeronautical and Space Sc Vol.12 No.3

This paper is focused on dynamic modeling and control system design as well as vision based collision avoidance for multi-rotor unmanned aerial vehicles (UAVs). Multi-rotor UAVs are defined as rotary-winged UAVs with multiple rotors. These multi-rotor UAVs can be utilized in various military situations such as surveillance and reconnaissance. They can also be used for obtaining visual information from steep terrains or disaster sites. In this paper, a quad-rotor model is introduced as well as its control system, which is designed based on a proportional-integral-derivative controller and vision-based collision avoidance control system. Additionally, in order for a UAV to navigate safely in areas such as buildings and offices with a number of obstacles, there must be a collision avoidance algorithm installed in the UAV's hardware, which should include the detection of obstacles, avoidance maneuvering, etc. In this paper, the optical flow method, one of the vision-based collision avoidance techniques, is introduced, and multi-rotor UAV's collision avoidance simulations are described in various virtual environments in order to demonstrate its avoidance performance.

A Preliminary Study of Korean Dual-Frequency SBAS

Yun, Ho,Han, Deokhwa,Kee, Changdon The Institute of Positioning 2014 Journal of Positioning, Navigation, and Timing Vol.3 No.1

A Satellite Based Augmentation System (SBAS) is a representative differential GNSS system, which is used for the navigation performance improvement of Global Navigation Satellite System (GNSS) users. SBAS has been developed focusing on the securement of user integrity so that it can be used for the navigation in aviation fields. Accordingly, the development of SBAS has been completed, and it has been actively used in the United States, Europe, and Japan. As the new satellite of Global Positioning System (GPS) recently started to broadcast new civil signals (L5 frequency), the methods for improving user navigation performance in SBAS using this signal have also been studied. In Korea, to keep pace with these circumstances, full-scale SBAS development is expected to start in 2014, and studies on dual-frequency SBAS using L1/L5 frequencies will also be performed. In this study, before the full-scale development of dual-frequency SBAS in Korea, a simulation was performed to predict the performance and analyze the expected effects.

Enhanced SBAS Integration Method Using Combination of Multiple SBAS Corrections

Yun, Ho,Kim, Do-Yoon,Jeon, Sang-Hoon,Park, Bynng-Woon,Kee, Chang-Don The Korean Society for Aeronautical and Space Scie 2009 International Journal of Aeronautical and Space Sc Vol.10 No.1

In this parer, we propose a new way of improving DGNSS service using combination of multiple SBAS information. Because SBAS uses Geostationary Earth Orbit (GEO) satellites, it has very large coverage but it can be unavailable in urban canyon because of visibility problem. R. Chen solved this problem by creating Virtual Reference Stations (VRS) using the SBAS signal [1]. VRS converts SBAS signal to RTCM signals corresponding its location, and broadcast the converted RTCM signals over the wireless internet. This method can solve the visibility problem cost effectively. Furthermore it can solve DGNSS coverage problem by creating just a transmitter instead of a reference station. Developing above method, this paper proposes the methods that integrate two or more SEAS signals into one RTCM signal and broadcast it. In Korea, MSAS signal is available even though it is not officially certified for Korean users. As a Korean own SBAS-like system, there is the internet-based KWTB (Korean WADGPS Test Bed) which we developed and released at ION GNSS 2006. As a result, virtually two different SBAS corrections are available in Korea. In this paper, we propose the integration methods for these two independent SBAS corrections and present the test results using the actual measurements from the two systems. We present the detailed algorithm for these two methods and analyze the features and performances of them. To verify the proposed methods, we conduct the experiment using the logged SBAS corrections from the two systems and the RINEX data logged at Dokdo monitoring station in Korea. The preliminary test results showed the improved performance compared to the results from two independent systems, which shows the potential of our proposed methods. In the future, the newly developed SBASs will be available and the places which can access the multiple SBAS signals will increase. At that time, the integration or combination methods of two or more SBASs will become more important. Our proposed methods can be one of the useful solutions for that. As an additional research, we need to extend this research to the system level integration such as the concept of the decentralized W ADGPS.

Application & evaluation of IFN-r assay as one of the control program for bovine tuberculosis in Korea

Yunho JANG(Yunho JANG),Tae-woon KIM(Tae-woon KIM),Min Kyu Jeong(Min Kyu Jeong),Yu sin Ok(Yu sin Ok),So yoon Ryoo(So yoon Ryoo),Bang-Hun HYUN(Bang-Hun HYUN),Jae Myung KIM(Jae Myung KIM) 한국예방수의학회 2018 한국예방수의학회 학술대회자료집 Vol.2018 No.-

Remedying Racial Profiling under the Fourteenth Amendment by Analogizing Batson v. Kentucky and State v. Soto

Yunho Yeom 한국형사법무정책연구원 2020 International Journal of Criminal Justice Vol.2 No.1

Staged hybrid treatment for giant thrombosed fusiform aneurysm

Yunho Noh,Sung Ho Lee,Seok Mann Yoon,송인학,오재상 대한뇌혈관외과학회 2021 Journal of Cerebrovascular and Endovascular Neuros Vol.23 No.4

Partially thrombosed intracranial aneurysm was difficult to treat because of higher recurrence rate compared to non-thrombosed saccular aneurysm. The author reports a case of partially thrombosed intracranial aneurysm causing transient ischemic symptom. A 40-year-old man presented with transient right hemiparesis. Brain magnetic resonance imaging (MRI) depicted low-signal intensity target-like mass lesion on left sylvian fissure, and magnetic resonance angiography (MRA) showed aneurysm on left middle cerebral artery bifurcation (MCBF), suggested thrombosed aneurysm. On operative finding, aneurysm wall had thick and atherosclerotic change, and it was fusiform aneurysm not saccular type. We initially planned direct clip for the aneurysm, but it was failed due to collapse of parent artery after clipping on aneurysm neck. To prevent ischemia, extracranial-intracranial bypass was performed and then thrombectomy with clip reconstruction. To remodeling the fusiform aneurysm, stent-assisted coiling was performed for remnant portion of aneurysm. With staged hybrid technique, giant thrombosed fusiform aneurysm was completely obliterated and the patient did not suffer any neurologic symptoms no longer.

Selective CO₂ Conversion at a Single Nickel Center by Using Bioorganometallic Methodology

Yunho Lee(이윤호) 한국고분자학회 2023 한국고분자학회 학술대회 연구논문 초록집 Vol.48 No.2

A Moderat ed Mediat ion model of t he Relat ionship between Part icipat ory Decision-making and Team Performance in Hotel Industry

Yunho Ji,Jangheon Han People&Global Business Association 2021 Global Business and Finance Review Vol.26 No.1

Purpose: This study aimed to verify the impact of participatory decision-making (PDM) on team performance (TPF) in the hotel s department/team. In particular, it investigated the role of a mediator for creative self-efficacy (CSE) in the relationship between PDM and TPF. This study determined the optimal decision-making process in a service organization by verifying the controlled mediating effect of collective efficacy (CEF) in the relationship among PDM, CSE, and TPF. Design/methodology/approach: In this study, the 242 samples comprised luxury hotel workers. The analysis verified the hypothesis set by means of causal correlations among four variables using regression analysis and the process macro developed by Hayes (2013). Findings: The study revealed significant effects through the medium of CSE, although PDM did not have a direct impact on TPF. The moderating mediating effect of CEF on the mediating effect of CSE in the relationship between PDM and TPF was statistically significant. Research limitations/implications: This study focused on luxury hotels. The same hierarchy and team culture were assumed without considering the specific characteristics of each hotel team or department. Originality/value: This study proposed a suitable decision-making process model for efficient operation and employee motivation in hotel companies. The findings will contribute to a horizontal and open organizational culture, as well as the spread of PDM.