Actuator and sensor fault isolation of nonlinear systems

This work considers the problem of isolating actuator and sensor faults in nonlinear systems. The key idea is to exploit the analytical redundancy in the system through state observer design. To this end, out of possible actuator and sensor faults, we consider subsets of faults, and design state observers and an associated residual that is only sensitive to faults in each subset. With the ability of detecting faults in a subset, they can be isolated by checking whether the corresponding residuals breach their thresholds. The proposed method enables differentiating between actuator and sensor faults while explicitly accounting for system nonlinearity. The effectiveness of the fault isolation design is illustrated using a chemical reactor example.