Bond Graph Model-based Quantitative FDI in Hybrid Systems

Bond Graph Model-based Quantitative FDI in Hybrid Systems 

The representation of a hybrid system model by means of a bond graph with system mode independent causalities has the advantage that a unique set of equations can be derived from the bond graph that holds for all system modes. Discrete switch state variables in these equations account for the system modes. In this chapter, this bond graph representation is used to derive analytical redundancy relations (ARRs) from the bond graph. The result of their numerical evaluation called residuals can serve as fault indicator. Analysis of the structure of ARRs reveals which system components, sensors, actuators or controllers contribute to a residual if faults in these devices happen. This information is usually expressed in a so-called structural fault signature matrix (FSM). As ARRs derived from the bond graph of a hybrid system model contain discrete switch state variables, the entries in a FSM are mode dependent. Moreover, the FSM is used to decide if a fault has occurred and whether it can unequivocally be attributed to a component. Finally, the chapter discusses the numerical computation of ARRs. 

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The book concludes with a discussion of the presented bond graph model-based quantitative approach to FDI in hybrid systems and recommends as a possible topic for further research the use of bond graph modelling in fault tolerant control of hybrid systems. 

In this book, a quantitative ARR based approach to FDI for systems described by a hybrid model will be pursued and hybrid models are represented by bond graphs. 

The previous chapters address various aspects of quantitative bond graph-based FDI and system mode identification for systems represented by a hybrid model. This chapter illustrates applications of the presented methods by means of a number of small case studies. The examples chosen are widely used switched power electronic systems. Various kinds of electronic power converters, e.g. buck- or boost converters, or DC to AC converters are used in a variety of applications such as DC power supplies for electronic equipment, battery chargers, motor drives, or high voltage direct current transmission line systems [1]. 

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