Anja Grosch

Approach service type D evaluation of the DLR GBAS testbed

Ground-based augmentation systems (GBAS) for satellite navigation are intended to replace the instrument landing system for precision approach of aircraft into an airport in the near future. Here, we show an evaluation of data collected during flight trials with the GBAS testbed of the German aerospace center with respect to requirements for the GBAS approach service type D. This service will permit approach and landing down to the zero visibility conditions of category IIIc approaches. We show output of all airborne monitors and the results of an integrity analysis. During all flight trials, the system performed within the required criteria for integrity, continuity, and availability.

Parametric study of loosely coupled INS/GNSS integrity performance

Low-cost inertial sensors have been in the focus of ongoing research since they enable a low priced and low complex way to increase the robustness and reliability of navigation systems, especially GNSS. In this paper, we analyze a loosely coupled INS/GNSS including evaluation of the inertial error propagation and robustness of the corresponding navigation integrity concept with respect to the inertial system parameters. Moreover, we analyze the system integrity performance in terms of overall system protection level dependent on the inertial sensor error model. We discuss and compare the expected performance of using either typical high-end, middle-grad, low-cost or a network of redundant low-cost IMUs in terms of integrity and GNSS coasting time. We show that a network of four independent and identical distributed and orthogonally mounted low-cost sensors boosts the integrity performance significantly and even outperforms the one of a higher grade sensor. Additionally we discuss the trade-off between inertial networks and increased system complexity with respect to integrity performance in this paper.

Redundant inertial-aided GBAS for civil aviation

In this article, we investigate the impact of redundant MEMS-IMU on a loosely coupled INS/GBAS system. Therefore, we considered and analyze the combined performance of three identically and orthogonally mounted low-cost IMUs. It is shown that due to the redundancy, the INS based position error is reduced by an average factor of two. In conventional GBAS, no position solution can be obtain while GPS outages which lead to a full system failure. It is demonstrated that our redundant INS/GBAS integration sufficiently bridges GPS outages up to 10 seconds. Hence, the system availability is significantly improved. Additionally, an integrity concept is introduced providing integrity information even in the case where no GPS solution is available. This is essential for all safety-of-life applications such as civil aviation. We analyze our concept both, analytically and by Monte-Carlo Simulations. Our investigations clearly show that the robustness of the GBAS can be dramatically increased while maintaining low-costs and low-complexity.

Snapshot residual and Kalman Filter based fault detection and exclusion schemes for robust railway navigation

Integrating satellite based navigation into the railway standard can enable reliable and cost-efficient railway navigation everywhere. This makes is very attractive for railway. Thus its integration is strongly supported within the European railway evolution program. However, railway environments exhibit many challenges. Local threats are major issues for robust GNSS based railway navigation. They cannot be observed by any augmentation methods and can cause hazardous misleading information. Hence, they form an integrity risk, which needs to be detected and mitigated by the onboard system. We analyze three different approaches suitable for railway: two snapshot approaches exploiting track constraints during or after the GNSS position determination, and a sequential approach using an Extended Kalman Filter. We derive global fault detection and exclusion (FDE) schemes for all three positioning methods. We measure their performance in terms of along track position accuracy and position uncertainty. Additionally, we investigate each schemes FDE quality in detail and clearly show that the innovation based FDE of the extended Kalman filter has the best performance in terms of along track position, fault detection capability and exclusion gain. All investigations are done via Monte-Carlo simulations. The considered scenario was extracted from data collected during a measurement campaign in Brunswick, Germany.

Integrated Inertial Navigation System with multiple APNT ranges: Expected performance and considerations

Inertial sensors constitute an essential part in civil avionics systems. It has also been identified as a required system to meet the foreseen availability requirements in the context of Alternative Position Navigation and Timing (APNT). For example, DME/DME/Inertial (DDI) is currently considered for RNAV 1.0 operations. In this work, we look beyond DDI and investigate the possibility of an integrated inertial system with multiple APNT ranges. Thanks to our simulation framework, we evaluate in different scenarios the integration of inertial system with ranging sources using real DME locations. Based on the results, we finally analyze and comment on the limitations, implications and issues of using tactical grade instead of navigation grade inertial sensors.

Detection of DME ranging faults with INS coupling

In order to guarantee availability and continuity in Alternative Position Navigation and Timing (APNT), inertial systems are considered to coast the navigation position in case of navaids coverage gaps. For instance, DME/DME/Inertial (DDI) is currently considered for RNAV 1.0 operations. However, in order to support future RNP operations, the accuracy is not the only requirement to be fulfilled and other safety checks and integrity measures must be provided. This work analyses different fault detection mechanism for a multi-DME/Inertial system based on the innovation sequence of a Kalman filter. We aim to detect both single bias and ramp type fault profiles using snapshot and sequential test statistics. We evaluate the algorithms using our simulation framework based on real DME locations and realistic sensor error models.