Failure prognosis

Root-cause detection Incipient fault detection Problem diagnosis Failure prognosis Post mortem... 

Finally, with regard to condition based maintenance (CBM) of engineering systems it is important to detect the initiation of incipient faults, to assess the current health of a system and to predict the remaining useful life (RUL) of a component that has become faulty. As bond graph modelling enables the systematic generation of ARRs for FDI, it can also support failure prognosis. 

Chapter 9 briefly consideres the use of ARRs derived from a bond graph for the purpose of failure prognosis for hybrid systems. 

Failure Prognosis for Hybrid Systems Based on ARR Residuals... 

Failure prognosis is an essential part of condition-based management (CBM) and numerous papers on CBM have been published [1, 4, 5]. Some research work on failure prognosis recently reported in the literature may be found in [2, 6-9]. 

Failure Prognosis Based on ARR Residuals Derived from a Bond Graph 223... 

In case multiple potential component faults may be the cause for the start of an abnormal behaviour of an ARR residual, then parameter estimation as part of fault isolation identifies the parameters that are going to deviate from their nominal values. For each of them, failure prognosis wUl have to identify a degradation model as a first step. This identification of degradation models can be performed in parallel. As a result, multiple faults may have different degradation profiles. 

ARRs deduced from a bond graph then capture the degradation trend of physical parameters. As a result, their residuals will not stay close to zero. When time progresses they will eventually intersect with a user set failure alarm threshold. Finally, as failure prognosis starts from an initial state provided by the monitoring system, i.e. initial conditions are known, the bond graph may be in integral causality. 

The focus of this book has been on the presentation of a bond graph model-based approach to FDI and failure prognosis for hybrid systems. It turns out that ARRs derived from a bond graph play a key role in all tasks that have been considered, in FDI, in system mode identification and in failure prognosis. Simulation results have been obtained by using the dassl solver as part of the open source software Scilab [5]. 

Prognosis Failure prognosis means the ability of an early detection and isolation of incipient faults that may lead to a component failure, to determine the progression of the fault and to predict the remaining useful life (RUL), i.e. the time to failure given the current state of a system. 

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