Approaches for vector control of induction motor without speed sensor

Vector control of induction motor without speed sensor is one of the most up-to-date researching subjects to the engineers in the fields of power electronics and control theory. The fundamental principle for realizing approaches has already been studied in past 15 years. It is rather important to know how did people overcome the issues for implementing a practical product. The basic methods except the adaptive observer will be reviewed here, along with their accompanying techniques for solving individual issues, such as instability due to the variation of stator and rotor resistance, how to avoid integrating calculation, multiple control-loop problems etc. Some newly developed approaches and proposals will also be introduced