Analysis of a simple feed back method in field-oriented control of an induction motor without speed and position sensor

One disadvantage of field-oriented control is the need for a mechanical sensor to detect the rotor speed. Omitting this speed (or position) sensor allows for a more robust drive and saves costs. On the other hand, the control structure then has to obtain the space phasor of the rotor flux from the measured electrical quantities of the terminal voltage and current. This is usually done by a voltage flux model. Especially in the range of low stator frequency, the performance of this model deteriorates due to wrong parameters and measurement errors. Taking the rotor equation into account and using the magnitude of the rotor flux as a stabilising feedback leads to a simple control structure. In this paper, a simplified method of this feedback structure is proposed and its advantages and limits are investigated.