On sensor fault diagnosis problem: Compensator design to non linear system in real time

In this paper, the design and real-time implementation of a compensator (controller-observer) for a nonlinear two-tank liquid level system, linearized at a specific operating point, is presented. The controller uses feedback of this estimated state by means of a Luenberger observer which, in turn, is used to generate a residual signal by comparing the estimated state with the real state. The evaluation of this residual signal allows establishing whether a fault occurred in the system. For the physical (real-time) implementation of the coupled two-tank system compensator, the LabVIEW® software from National Instruments, and its corresponding USB data acquisition, were used. The conducted experiments demonstrate the satisfactory performance of the compensator, and in order to test its effectiveness in fault diagnosis, a real-time simulation with faults in the liquid level sensors of the system was carried out.