Steady-state speed sensor fault detection in induction motors with uncertain parameters: A matter of algebraic equations

This paper moves in the context highlighted in the recent literature, in which full and partial rotor speed sensor faults in induction motors with uncertain parameters can be detected by a single adaptive observer. Certain relevant experimental evidences concerning the use of such single adaptive observer in the aforementioned context, however, are yet to be theoretically motivated. Such evidences go beyond the already presented analyses and refer to the convergence of the resulting observer estimates under generating operations. In this paper, we present an algebraic equations-based analysis that extends any previous one, by providing a definite answer to the above question. It simultaneously clarifies any structural intrinsic limitation that is related to previously proposed approaches. The key point relies on deriving the explicit expressions for two admissible motor model solutions, which are characterized by the same output (rotor speed and stator currents) and input (stator voltages) profiles and whose existence is definitely linked to the adaptive observer behaviour in speed sensor fault detection scenarios.