Navigation Safety Assurance of a KF-Based GNSS/IMU System: Protection Levels Against IMU Failure

Abstract

This study introduces a navigation integrity and continuity algorithm against an inertial measurement unit (IMU) sensor fault within a Kalman filter (KF) that ensures a high level of safety for IMU-integrated safety-critical navigation applications. A representative example of an IMU integrated navigation system is a global navigation satellite system (GNSS)/IMU system. Most previous stud ies have focused on GNSS faults when evaluating the integrity and continuity of a KF-based GNSS/IMU navigation system, leaving the IMU fault hypothe- sis unaddressed. Unlike GNSS, which is applied in the measurement update step within the KF, IMU measurements are applied in the state prediction step, which results in different fault propagation characteristics in the user state error compared with those in GNSS. This paper analytically derives the sequen- tial IMU fault impacts on user state errors. Based on this investigation, a KF innovation-based fault detector and protection-level equations are developed, which can safely bound user state errors against sequential IMU fault impacts.