局域增强系统(LAAS)地面主控站(LGF)广播的差分修正量所包含的非零均值高斯误差和非高斯误差对系统的可用性造成较大的威胁。为此,提出一种均值膨胀和非高斯膨胀相结合的算法以改进传统的sigma膨胀算法。通过恰当地选取各膨胀系数,采用改进算法可在满足各类型误差尾部覆盖的同时,还可有效提高系统的可用性水平。计算机仿真结果表明:与传统的sigma膨胀算法相比,在无卫星故障时,改进算法可将系统可用性水平提高至99.99%;在关键卫星发生故障时,改进算法的可用性增益可提高18.97%,同时可用性水平可提高至95.24%。
The non-zero mean Gaussian error and the non-Gaussian error contained in the differential corrections which are broadcast from the local area augmentation system (LAAS) local ground facility (LGF) pose a strong threat to the integrity monitoring of signal-in-space. This paper advances an algorithm in which the mean inflation and non-Gaussian inflation are combined to improve the traditional sigma inflation. By selecting the appropriate inflation coefficients, the proposed method is not only able to overbound the tails of predefined errors, but also enhance effectively the LAAS availability level. Computer simulation results indicate that compared with the sigma inflation scheme, the availability level can be as high as 99.99% in the case of a fault-free satellite. Even in the case of a critical satellite failure, the availability benefit of the algorithm could be improved 18.97% and the availability level could be raised to 95.24%.
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