Diagnosability analysis of an ABS system modeled using Petri nets

We consider the braking system of a vehicle equipped with an ABS. In a previous paper we presented a Petri net model of such a device assuming that the sensor that activates the ABS can be affected by a stuck-at-on fault. Here, the case in which the ABS sensor can be affected by both a stuck-at-on and a stuck-at-off fault is considered. Firstly, we consider the case in which the braking subsystems of different wheels cannot exchange information neither between them, nor with a coordinator. We show that in this local setting, where diagnosis is performed independently at each wheel, faults are not diagnosable. Secondly, we show that in a centralized setting, where the diagnoser can monitor each single wheel, the overall system is diagnosable. Finally, we assume that the braking systems of two wheels on the same side of the vehicle can exchange information and propose a communication protocol that makes the overall system diagnosable assuming both wheels are always in the same grip condition.