Failure detection and isolation structure for global positioning system autonomous integrity monitoring

In this paper, a new failure detection and isolation (FDI) structure is investigated for global positioning system (GPS) integrity monitoring in an integrated inertial navigation system (INS)/GPS navigation system. In the structure, a bank of auxiliary integrated INS/GPS Kalman filters, each of them processing a subset of the GPS measurements, are applied to provide high-accuracy detection references. The failure detection is then undertaken by checking the consistency between the state estimate of the main integrated INS/GPS Kalman filter and the auxiliaries. Two state propagators are also included in the FDI structure to reliably isolate the failed GPS measurement. The two propagators are alternatively reset with the data of the Kalman filter to increase their accuracy and thereby the failure isolation performance. The failure isolation is realized by testing the consistency between the state estimates of the auxiliary Kalman filters and the state propagator. The simulation results show that the FDI structure is capable of not only detecting the presence of a malfunctioning satellite that results in a large range error, but also identifying which satellite is malfunctioning.