Methods for Fault Diagnosability Analysis of a Class of Affine Nonlinear Systems

The fault diagnosability analysis for a given model, before developing a diagnosis algorithm, can be used to answer questions like “can the fault be detected by observed states?” and “can it separate fault from fault by observed states?” If not, we should redesign the sensor placement. This paper deals with the problem of the evaluation of detectability and separability for the diagnosability analysis of affine nonlinear system. First, we used differential geometry theory to analyze the nonlinear system and proposed new detectability criterion and separability criterion. Second, the related matrix between the faults and outputs of the system and the fault separable matrix are designed for quantitative fault diagnosability calculation and fault separability calculation, respectively. Finally, we illustrate our approach to exemplify how to analyze diagnosability by a certain nonlinear system example, and the experiment results indicate the effectiveness of the fault evaluation methods.