Fault detection in closed-loop systems using a double residual generator

A double residual generator for fault detection in closed-loop systems is presented in this paper. The residual generator gives the standard residual vector and a dual residual vector as outputs. The standard residual vector can be applied directly for fault detection. The dual residual vector depends on known inputs to the system e.g. reference inputs and auxiliary inputs but decoupled from the disturbance in the system. It is also an input vector that can be applied for active fault detection (AFD). The dual residual vector can be considered as a generalized input vector in connection with AFD in closed-loop systems. This gives the possibility to use all known inputs for detection. The dual residual vector gives a link between passive and AFD in closed-loop systems. The double residual generator is given directly as the left Bezout matrix from the Bezout equation.