Detection of scramjet unstart in a hypersonic vehicle model

An observer-based strategy for the detection of engine unstart in a scramjet-powered hypersonic vehicle model is presented in this paper. The occurrence of engine unstart, which is regarded as an actuator fault, causes a transition from an operational vehicle mode in which the engine is controllable to a mode where the vehicle is effectively unpowered. Since this transition is accompanied by an abrupt change in model parameters, the vehicle dynamics is modeled as a switching system. A simple algorithm is derived that detects the occurrence of the transition from “started” to “unstarted” mode by processing only the flight control system data, without relying on engine data or measurement of the airflow across the isolator, which facilitate integration with existing control architectures. The method is shown to possess a certain degree of robustness with respect to perturbation on model parameters. Simulation results show the effectiveness of the proposed approach.