• Journal of Navigation and Port Research
• /
• v.33 no.6
• /
• pp.395-400
• /
• 2009

In order to prepare for the DGNSS recapitalization and implementation of the functions for software based reference station and integrity monitor (RSIM) system, this paper proposes a design of integrity monitor functions of maritime differential GPS RSIM. The most critical functions of the integrity monitor (IM) are to generate and send flags to the reference station (RS) along with system feedback. Firstly, it presents the architecture of software based RSIM, and analyzes the performance standard of integrity monitor for maritime DGPS reference station This paper then designs the functions of integrity monitor for DGPS reference station based on the performance standard. Finally, this paper presents the results of performance analysis for the functionality of integrity monitor using the GNSS simulator. it discusses the study method and its application for the system implementation.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.5 no.2
• /
• pp.13-19
• /
• 2009

As the operating time in nuclear power plants (NPPs) increases, the integrity of nuclear components may be continually degraded due to aging effects of systems, structures and components. Recently, a number of NPPs are being operated beyond their design life to produce more electricity without shutting down. The critical issue in extending a lifetime is to maintain the level of safety during the extended operation period while satisfying the international regulatory standards. Therefore, it is beneficial to build a monitoring system to measure an aging status. In this paper, the Aging Monitor (AM) based on lots of aging database obtained from the operating plants and research results on the aging effects was developed to monitor, manage and evaluate the aging phenomena systematically and effectively in NPPs. The AM for the CANDU is divided into 6 modules: (1) Aging Alarm/Coloring Monitor, (2) Aging Database, (3) Aging Document, (4) Real-time Integrity Monitor, (5) Surveillance and Inspection Management System, and (6) Continued Operation and Periodic Safety Review (PSR) Safety Evaluation. The proposed system is expected to provide the integrity assessment for the major mechanical components of an NPP under concurrent working environments.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.22 no.3
• /
• pp.328-333
• /
• 2012

Current differential GPS (DGPS) system consists of reference station (RS), integrity monitor (IM), and control station (CS). The RS computes the pseudorange corrections (PRC) and generates the RTCM messages for broadcasting. The IM receives the corrections from the RS broadcasting and verifies that the information is within tolerance. The CS performs realtime system status monitoring and control of the functional and performance parameters. The primary function of a DGPS integrity monitor is to verify the correction information and transmit feedback messages to the reference station. However, the current algorithms for integrity monitoring have the limitations of integrity monitor functions for satellite outage or anomalies. Therefore, this paper focuses on the detection and identification methods of satellite anomalies for maritime DGPS RSIM. Based on the function analysis of current DGPS RSIM, it first addresses the limitation of integrity monitoring functions for DGPS RSIM, and then proposes the detection and identification method of satellite anomalies. In addition, it simulates an actual GPS clock anomaly case using a GPS simulator to analyze the limitations of the integrity monitoring function. It presents the brief test results using the proposed methods for detection and identification of satellite anomalies.

• Journal of Advanced Navigation Technology
• /
• v.21 no.1
• /
• pp.12-20
• /
• 2017

A maritime DGPS in Korea offers pseudo-range correction information and monitors integrity of correction data by using multiple GNSS receivers. The maritime DGPS reference station and integrity monitor service sets alarm threshold value about integrity monitoring parameters for preventing service interruption status. However there is no way to avoid system interruption according to malfunction of backup systems and outside factors. Therefore, in this paper, warning threshold values were proposed for maritime DGPS operator can be counteract in advance. And Markov analysis method was carried out for selection of these warning threshold values.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.601-605
• /
• 2007

This paper describes the experimental method to monitor the structural integrity. The crack on structures changes the wave propagation characteristics of structures. To monitor this change, frequency dependent variation of dynamic stiffness of beam structures is obtained by using beam transfer function method, and its trends are compared to undamaged one for identifying the location and size of the crack. Piezoelectric actuators were used to generate flexural vibrations. It eliminated various restrictions of continuously measuring wave propagation characteristics and monitoring structural integrity. The structural integrity was identified with minimal number of measurements and smart structures employing PZT actuations.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.8
• /
• pp.781-789
• /
• 2010

In the GPS/INS integrated system fault detection, algorithm based on a chi-square distribution is commonly used. In this paper, it has been proposed simplified GPS/INS fault detection algorithm that is combined conventional RAIM (Receiver Autonomous Integrity Monitor) and algorithm based on chi-square distribution for UAV using row-grade processor. It use a fault model to verify the proposed algorithm and produced the result.

• Journal of Positioning, Navigation, and Timing
• /
• v.12 no.1
• /
• pp.51-58
• /
• 2023

Geofencing supports unmanned aerial vehicle (UAV) operation by defining stay-in and stay-out regions. National Aeronautics and Space Administration (NASA) has developed a prototype of the geofencing function, SAFEGUARD, which prevents stayout region violation by utilizing position estimates. Thus, SAFEGUARD depends on navigation system performance, and the safety risk associated with the navigation system uncertainty should be considered. This study presents a methodology to compute the safety risk assessment-based along-track position error bound under nominal and Global Navigation Satellite Systems (GNSS) failure conditions. A Kalman filter system using pseudorange measurements as well as pseudorange rate measurements is considered for determining the position uncertainty induced by velocity uncertainty. The worst case pseudorange and pseudorange rate fault-based position error bound under the GNSS failure condition are derived by applying a Receiver Autonomous Integrity Monitor (RAIM). Position error bound simulations are also conducted for different GNSS fault hypotheses and constellation conditions with a GNSS/INS integrated navigation system. The results show that the proposed along-track position error bounds depend on satellite geometries caused by UAV attitude change and are reduced to about 40% of those of the single constellation case when using the dual constellation.

• Journal of Positioning, Navigation, and Timing
• /
• v.3 no.1
• /
• pp.17-23
• /
• 2014

Satellite Based Augmentation Systems (SBAS) provide ionospheric corrections at geographically five degree-spaced Ionospheric Grid Points (IGPs) and confidence bounds, called Grid Ionospheric Vertical Errors (GIVEs), on the error of those corrections. Since the ionosphere is one of the largest error sources which may threaten the safety of a single frequency Global Navigation Satellite System (GNSS) user, the ionospheric correction and integrity bound algorithm is essential for the development of SBAS. The current single frequency based SBAS, already deployed or being developed, implement the ionospheric correction and error bounding algorithm of the Wide Area Augmentation System (WAAS) developed for use in the United States. However, the ionospheric condition is different for each region and it could greatly degrade the performance of SBAS if its regional characteristics are not properly treated. Therefore, this paper discusses key factors that should be taken into consideration in the development of the ionospheric correction and integrity bound algorithm optimized for the Korean SBAS. The main elements of the conventional GIVE monitor algorithm are firstly reviewed. Then, this paper suggests several areas which should be investigated to improve the availability of the Korean SBAS by decreasing the GIVE value.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.28 no.6
• /
• pp.1553-1561
• /
• 2018

The source code for Android is open and easy to modify depending on the purpose. Recently, this charateristic has been exploited to bypass the runtime protection technique and extract the original executable code. Unfortunately, Android devices are so fragmented that it is difficult to verify the integrity of the system. To solve this problem, this paper proposes a technique to verify the integrity of the execution environment indirectly using the features of the application permission. Before executing the original executable code, it loads and executes the dummy DEX file to monitor for abnormal events and determine whether the system is intact. The proposed technique shows a performance overhead of about 2 seconds and shows that it can detect the bypassing technique that is currently disclosed.

• Journal of Positioning, Navigation, and Timing
• /
• v.11 no.4
• /
• pp.317-325
• /
• 2022

In this paper, we developed a single frequency-based RRAIM to monitor integrity of the UAM landing vertically in urban area with only low-cost single-frequency GPS receiver. Conventional dual-frequency RRAIM eliminates ionospheric delay through a combination of frequencies. In this study, ionospheric delay was directly modeled. Drift error of residual ionospheric delay is modeled using the previously studied result on ionospheric rates of change. To verify the performance of the proposed RRAIM algorithm, a simulation of vertical landing UAM in urban area was conducted. It was assumed that the protection level at the initial position was calculated through SBAS correction data. During vertical landing, integrity monitored by receiver alone without external correction data. In the 60 sec simulation, the protection level of the proposed RRAIM compared to the conventional RRAIM was calculated to be 140% due to the accumulated ionospheric delay error. Nevertheless, it was confirmed that the final vertical protection level meeting the requirements of LPV-200, which cannot be achieved with single frequency GPS receiver alone.