Detection and Isolation of Speed-, DC-Link Voltage-, and Current-Sensor Faults Based on an Adaptive Observer in Induction-Motor Drives

A sensor fault detection and isolation unit is considered for induction-motor drives based on an adaptive observer with rotor-resistance estimation. Generally, closed-loop induction-motor drives with voltage-source inverters use a speed or position, a dc-link voltage, and two or three phase-current sensors. In the proposed fault-detection and isolation unit, the estimated phase currents and rotor resistance are sent to a decision-making unit, which identifies the faulty sensor type based on a deterministic rule base. In the case of a current-sensor failure, it also detects the phase with erroneous sensor output. It is shown that, unlike the other proposed model-based fault-tolerant systems, using a bank of observers is not necessary, and only one current observer with rotor-resistance estimation is sufficient for isolation of all sensors´ faults. The accuracy of the proposed approach is analytically proved. Furthermore, extensive simulation and experimental tests verify the effectiveness of the proposed method at different operating conditions.