Study of prognostic algorithms for electrohydraulic actuators applied to aerospace systems

The purpose of this dissertation is to conduct prognostic analysis on a numerical model of an electrohydraulic actuator - used in aerospace environments - to permit early proactive maintenance on the physical system, beneficial for its lifespan extension. The detailed model of a flapper-nozzle servo valve is used to help identify and analyze possible alterations on the dynamical response by applying several types of commands and faults (single or multiple). The main types of commands used in this study are: a basic ramp command, a chirp command with decrescent amplitude, and a mixed time-history command for prognostic purposes. The faults I examined are backlash and increasing dynamic friction on the actuation jack. A comparation between the responses of the detailed model and of a simpler monitoring model is presented to evaluate appreciable differences. Then, the parameters of the monitoring model are modified through appropriate optimisation algorithms to minimize errors between the dynamic responses of the two models. Fault identification is achieved through the correlation of their scale with the variation of aforementioned parameters.