Towards A Complete FMEA Method to Assess the Performance of GPS system for GPS based applications

R. Ioannides, D. Walsh, W. Ochieng and S. Feng

Abstract:	Failure mode effect analysis (FMEA) methods attempt to analyse the effects of failures on GPS performance by characterising the GPS failure modes and assess their impact on GPS based applications. There are a number of limitations, arising from the complexity of the system, that have to be overcome for validating GPS-based applications, in the presence of the GPS failure modes. To the best knowledge of the author there is no complete FMEA process that can be followed to assess the performance of the system specifically for GPS based flight operations. The intention of this paper is to present a new complete FMEA process for validating GPS based flight operations that can be used to accurately determine the performance of the system for any GPS based application. Geometry is one of the three factors, the other two being biases and nominal range errors, that are key to the assessment of the performance of a satellite based navigation system, like GPS or Galileo. For overcoming the limitations imposed by the complexity of the GPS on FMEA processes used to assess the performance of the system in the presence of these failures, the effect of the geometry had to be analysed and link its effects with the GPS failure modes which has been a major task of this work. In order to identify the geometry parameters that can be used to accurately predict the impact of geometry on the performance of the system required the investigation of several geometry factors starting from the concept of slope. In this paper we also present two new geometry parameters, PB and BT that can be directly calculated from the equation of the slope. PB is defined as the ratio of the position error over the bias applied to the faulty satellite, while BT is defined as the ratio of the bias applied to the faulty satellite over the test statistic contribution due to that bias. These geometry parameters have been tested for evaluating their consistency in predicting the performance of the system linking the geometry effects of the GPS system to the GPS failure modes but also for assessing the performance of the currently used RAIM algorithms.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	1826 - 1840
Cite this article:	Ioannides, R., Walsh, D., Ochieng, W., Feng, S., "Towards A Complete FMEA Method to Assess the Performance of GPS system for GPS based applications," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 1826-1840.
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