Gi-Wook Nam

GNSS integrity Performance analysis in Korean region

this paper, integrity analysis in Korean region using GPS, modernized GPS, Galileo, SBAS and GBAS is given. The simulation results show that Cat. I requirement can be met using modernized GPS and Galileo alone, however, Cat. II and III are not met even augmenting SBAS because of VPL. A more efficient augmentation such as GBAS reduces VPL to meet Cat. II and III requirements in Korean region. This result will be used to design and implement not only an augmentation system but also regional satellite navigation system.

GBAS Reference Receiver Clock Adjustment Effects on Continuity and Integrity Performance

Ground-based augmentation system (GBAS) reference stations provide pseudo-range corrections (PRCs) and range rate corrections (RRCs) for visible GPS satellites along with the standard deviations of the PRC errors (σpr_gnd) and B-values for the reference receivers. When generating PRCs, a GBAS should adjust the reference receiver clock bias to limit the PRC values within a certain range specified by international standards. Since σpr_gnd should reflect the PRC errors accurately for system integrity, it must consider the effect of the clock adjustment procedure. Nevertheless, this has hardly been researched, since it is well known that the clock adjustment does not impact on the user position solution. This paper notices that σpr_gnd is also used for GBAS integrity monitoring functions which are implemented in range domain, not position domain. Thus, the work presented here investigates continuity and integrity performance risk in range domain in case a GBAS estimates σpr_gnd ignoring the clock adjustment procedure and uses it for integrity monitors. The work presented here analyzes the risk by a simulation and proposes strategies for σpr_gnd establishment considering the clock adjustment effects to prevent system performance risk.

Statistical Test for Performance Evaluation of Code Carrier Divergence Detection at a GBAS Reference Station

In order to provide precision approach service based on GBAS, air navigation service providers should validate the GBAS system performance against international standard requirements and receive approval. The GBAS manufacturer should define integrity threat, analyze the integrity monitors and evaluate performance of the implemented monitors to verify integrity performance which is critical to the aircraft safety. This paper describes a statistical test result to evaluate performance of the code carrier divergence monitors implemented in KARI Integrity Monitor System software. The paper introduces analysis and test procedure which is developed for the performance evaluation and describes the analysis, the test scenario generation and the test results. The results show that the implemented monitors can detect the expected minimum detectable errors with satisfying the probability of missed detection requirements.

Obstacle Avoidance of GNSS Based AGVs Using Avoidance Vector

The Global Navigation Satellite System(GNSS) is being utilized in numerous applications. The research for autonomous guided vehicles(AGVs) using precise positioning of GNSS is in progress. GNSS based AGVs is useful for setting driving path. This AGV system is more efficient than the previous one. Escipecially, the obstacle is positioned the driving path. Previcious AGVs which follow marker or wires laid out on the road have to stop the front of obstacle. But GNSS based AGVS can continuously drive using obstacle avoidance. In this paper, we developed collision avoidance system for GNSS based AGV using laser scanner and collision avoidance path setting algorithm. And we analyzed the developed system.

Steering Performance Test of Autonomous Guided Vehicle(AGV) Based on Global Navigation Satellite System(GNSS)

In this paper, a GNSS-based AGV system was designed, and steering tested on a golf cart using electric wires in order to confirm the control efficiency of the low speed vehicle which used only position information of GNSS. After analyzed the existing AGVs system, we developed controller and steering algorithm using GNSS based position information. To analyze the performance of the developed controller and steering algorithm, straight-type and circle-type trajectory test are executed. The results show that steering performance of GNSS-based AGV system is ± 0.2m for a reference trajectory.