Evaluating the quality of WAAS availability control algorithm under geomagnetic storm conditions

Introduction: The Wide Area Augmentation System (WAAS) is vulnerable to false alarms about the violation of the required navigation parameter availability under geomagnetic disturbances. As a consequence, the system operation efficiency might decrease because of a mismatch between the output of the control system and the actual quality of the navigation-time support. Purpose: Comparative analysis of the actual quality of navigation-and-time support for GPS users and the output information of the system for monitoring the availability of the required WAAS navigation parameters under a moderate magnetic storm and with technical failures during the operation of separate segments of GPS and WAAS systems. Results: Location errors were calculated for 82 reference stations in the USA equipped with GPS navigation receivers. The calculations used the geometric ranges of visible navigation satellites and the corresponding real values of the ionospheric range-measurement error determined by the method of two-frequency measurements. Based on the same data and through the use of the conventional standard WAAS availability control algorithm, the user protection levels were calculated in the horizontal and vertical planes. The results of these calculations are presented as a time graph of WAAS operating area coverage percentage, which was compared with the respective graphs presented in the official WAAS work reports. It is established that there are cases of significant discrepancy between the forecasts about the availability of the required navigation parameters according to the WAAS data and the real quality of positioning in the operating area of this system. There are discrepancies in the results of calculations of protection levels in the horizontal and vertical planes obtained from official reports on the operation of the system and in calculations based on the geometric range and real ionospheric range-measurement error. Practical relevance: Recommendations are proposed in order to reconsider the development of a navigation parameter availability control for wide-area augmentation systems, splitting the calculation into “locally dependent” and “globally dependent” components of differential corrections of range-measurement errors. It will reduce the likelihood of false alarms or dangerous inconsistencies in information within the system.

Optimization of potential field parameters using genetic algorithm

This paper addresses a metaheuristics approach to optimize the parameters of the potential fields (PF) method. This method is an important algorithm and is primarily used for local navigation problems. However, estimating the appropriate parameters is essential for safe and smooth navigation. For instance, complex scenarios that include long and thin corridors or cluttered environments having numerous obstacles require reliable parameter estimation. Accordingly, the genetic algorithm is utilized to estimate the appropriate algorithms to overcome conventional navigation problems based on the PF method. The experimental results verify the reliability and efficiency of the proposed approach. Keywords: Path planning, potential fields (PF) method, genetic algorithm (GA), DEAP, robot navigation, parameter optimization.

The Research of SINS Algorithm Based on Screw Compensation

In order to eliminate the non-commutative error which generates in calculating navigation parameter based on quaternion algorithm, the navigation algorithm based on screw theory is studied in this paper to meet the need of high-precision navigation. Navigation solver mathematical model of SINS is established. Based on screw compensation algorithm, the simulation with the trajectory data of the shell had been done. And it had been compared to the quaternion rotation vector method. The simulation results show that compared to the rotation vector algorithm, the accuracy of attitude has little difference, but the accuracy of velocity and the accuracy of position are both relatively higher precision.