Robust Fault Diagnosis based on Constraint Satisfaction and Interval Continuous-time Parity Equations

Abstract

This paper deals with fault diagnosis for a class of nonlinear continuous-time systems based on an interval extension of continuous-time parity equations. The parity equations are designed based on ordinary differential equations modeling some links between the successive output and input vector derivatives. The noisy inputs and outputs are evaluated through a high-order sliding-mode differentiator. The redundancy relations are formulated as a Constraint Satisfaction Problem (CSP) with faults as unknown variables. In this case, a reliable estimation of the fault magnitude can be performed by solving the CSP using interval techniques. This technique is well suited to deal with actuator faults as well as parametric or sensor faults. However, in this paper, we choose to focus on actuator faults and the performance of the proposed approach is illustrated through simulations on oscillatory failure detection in aircraft surface servo loops. input observer, fault reconstruction, consistency techniques, nonlinear systems.