DESIGN OF A CONFIDENCE INTERVAL OBSERVER -APPLICATION TO VEHICLE POSITIONING

Abstract

State estimation methods allow the vehicle position and velocity to be reconstructed by combining information from sensors and vehicle model. From a security point of view, position and velocity have to be known with a high level of confidence in order, for example, to avoid vehicle collision. In this paper, a confidence interval observer is developed to enclose positioning variables with some confidence degree (or integrity level). Based on a vehicle model and intervals bounding, with some associated probability, the uncertain initial conditions, inputs, model parameters and measurements, a predictor provides intervals for the state estimate trajectory between two measurement times. At each measurement time, confidence intervals from the sensors and the predictor are combined with union and intersection operations so as to satisfy the specified integrity level. Finally, the shortest non-empty intervals are chosen among the safe intervals. This method is illustrated with simulation tests based on an autonomous underwater vehicle described by a nonlinear model.