Fault-tolerant and Diagnostic Methods for Navigation

Precise and reliable navigation is crucial, and for reasons of safety, essential navigation instruments are often duplicated. Hardware redundancy is mostly used to manually switch between instruments should faults occur. In contrast, diagnostic methods are available that can use analytic redundancy to diagnose faults and autonomously provide valid navigation data, disregarding any faulty sensor data and use sensor fusion to obtain a best estimate for users. This paper discusses how diagnostic and fault-tolerant methods are applicable in marine systems. An example chosen is sensor fusion for navigation. Diagnosis design is based on parity relations and statistical hypothesis tests. Sensor fusion on healthy signals is made using a Kalman filter with inverse covariance updating to deal with asynchronous or missing data from instruments. The paper is presented at a tutorial level.