Experiments on actuator fault diagnosis: The case of a nonlinearly controlled AC motor

At the present days, the AC motors is an industrial standard, not only in high power constant speed applications, but also in the medium and low power range. With the diffusion of induction motors some crucial problems emerged: (i) to control the AC drive in order to achieve high dynamic performances; (ii) to monitor the induction motor, with the aim to detect the most common faults. Several types of nonlinear controllers/observers were developed, to solve the control problem. In this paper we introduce a novel approach to fault diagnosis of an AC drive, controlled by a feedback linearizing controller together with a proper nonlinear observer. We propose to investigate the tracking errors, that are generated by this control scheme, with the aim to monitor the integrity of the motor itself. Simulation results on a model of a real AC motor are reported showing that the tracking errors can be used as fault symptoms.