On Integrity Monitoring of Integrated Navigation Systems

Sammanfattning: In civil aviation a new philosophy for flight safety and traffic management is under development. The goal is to enable an expected increase in air traffic density by reducing aircraft separation. The accuracy of the position estimate determined by the navigation system in each aircraft determines this separation. A necessary component to achieve this goal is a monitor that continuously supervise the navigation solution integrity, i.e., the trust that can be placed on the estimated position. Integrity monitoring is important in military applications as well.In this thesis the problem of monitoring the integrity of navigation systems is studied. Most of the proposed methods for integrity monitoring of navigation systems are formulated in a very problem oriented manner. The problem has close connections to fault detection and isolation and many connections with general methods within this area have been found and are pointed out. The thesis contains surveys on both navigation and fault detection and isolation.When using multiple navigation sensors, they could be integrated to yield better performance as well as integrity. A multi-level monitoring scheme to be used in an integrated navigation system is proposed. The scheme uses different integrity monitoring approaches at different levels to achieve improved total performance.Furthermore, one method, the Generalized Likelihood Ratio GLR test, is evaluated for integrity monitoring of an integrated inertial/satellite navigation system (INS-GNSS). In addition to prove good detection performance of the GLR test special attention is given to two problems related to the navigation application, tuning of the GLR test and fault isolation. Good fault isolation together with the GLR test statistics form the basis for compensation of the position estimate after a detected fault.The proposed methods for tuning, detection and isolation are evaluated on a simulated model of the North pointing channel of an integrated inertial-satellite navigation system.