Degenerate Motions of Multisensor Fusion-Based Navigation

The system observability analysis is of practical importance, for example, due to its ability to identify the unob- servable directions of the estimated state which can influence estimation accuracy and help develop consistent and robust es- timators. Recent studies focused on analyzing the observability of the state of various multisensor systems with a particular interest in unobservable directions induced by degenerate mo- tions. However, those studies mostly stay in the specific sensor domain without aiding to extend the understanding to other heterogeneous systems. To this end, in this work, we provide degenerate motion analysis on general local and global sensor- paired systems, offering insights applicable to a wide range of existing navigation systems. Our analysis includes 9 degenerate motion identification including 5 already identified in literature and 4 new motions with both synchronous and asynchronous sensor-pair cases. Comprehensive numerical studies are con- ducted to verify those identified motions, show the effect of degenerate motion on state estimation, and demonstrate the generalizability of our analysis on various multisensor systems.