Hierarchical diagnosis for an overactuated autonomous vehicle

The paper presents a new strategy based on hierarchical diagnosis for an autonomous four-wheel steering four-wheel driving (4WS4WD) electrical vehicle. It is known that the lateral stability of the vehicle may be lost in specific faulty scenarios (due, for instance, to the front wheels steering mechanism faults, wheels blocking or drop of pressure). We propose a hierarchical diagnosis to ensure the stability of the vehicle when isolating precisely the component fault. When the vehicle lateral error exceeds a threshold, a dynamic reference generator for rear wheels steering actuator is activated in order to guarantee the vehicle´s lateral stability. Simultaneously, an active diagnosis based on the rear wheels steering mathematical model is used to identify the tire-road interface, a vital information for detecting and isolating faults when using analytical redundancy based residuals. The strategy proposed is tested and validated on a realistic dynamic vehicle model simulated using CarSim and Matlab-Simulink softwares.