Simple sensorless control of induction machine with on-line parameter identification

Various approaches have been proposed in the literature for estimation of speed using only the terminal quantities of the motor, eliminating the speed sensor at the machine shaft. Many earlier proposed methods suffer from the problems of the open loop integration by analogue technique and parameter sensitivity. Nowadays the computing power provided mainly by the digital signal processors, makes it possible to overcome these problems by implementing and improving the previously proposed methods on a sophisticated hardware. In this paper a simple, easily implementable method is presented for the sensorless control of induction motor drive. Using the induction machine equations (state equations), it is based on a combined model, derived from the usual models of the induction machine. The terminal voltage and current of the machine should be measured for speed calculation. By the proposed model not only the speed, but one of the motor parameters can be estimated. A simple method is derived for the rotor resistance on-line identification. The problems of the practical implementation are investigated.