Parameter sensitivity analysis of an improved open-loop speed estimate for induction motor drives

In the last decades, several schemes have been proposed for speed-sensorless control of induction motor drives. Promising approaches are closed-loop observers, as model reference adaptive systems (MRAS) and Kalman filters, and open-loop estimators, which have recently aroused lively interest because of their simplicity and low-cost profile. As known, open-loop algorithms use only motor equations to derive the speed estimation, whose accuracy turns out to be strictly related to the motor model and its parameters. This paper presents an improved open-loop speed estimation algorithm, which uses reference voltages and measured currents, after that a state-of-the-art dead time compensation has been performed. The often undervalued topic of parameter sensitivity is handled by an accurate mathematical investigation, confirmed by a complete set of both simulated and experimental results. The estimated speed is then used as feedback signal in a closed loop speed control, and a performance evaluation is accomplished as well.