A Study on Fault-Tolerant Integrated Navigation Systems

Abstract

In this chapter, navigation systems that comprise onboard inertial measurements with external aids, such as Global Positioning System (GPS) or Doppler radar, are considered. The objective of such systems is to reliably estimate the navigation states, which include the position and velocity of the vehicle, from the inertial measurements and the external aids despite the possible occurrence of faults in the inertial measurement unit (IMU) or in the external measurements. Approaches are reviewed for detecting and isolating faults in strapdown inertial measurements, for combining the estimates of the navigation states from subsystems that each use only a subset of the available external measurements, and for detecting the presence of a fault in the external measurement data and avoiding its use in constructing a global navigation state estimate. Finally, a fault-tolerant, integrated navigation system (INS) architecture is suggested which produces a global estimate of the navigation states from two aided navigation subsystems, one combining inertial data with GPS data, and the other combining inertial data with Doppler radar data, which can tolerate IMU faults, one GPS fault, and one Doppler radar fault. Simulation results for one particular mission with selected faults included demonstrate that the suggested architecture is tolerant of these faults in the sense that the navigation state estimates are unaffected.