Sensorless control of permanent magnet synchronous motor — a survey

Vector control has been widely used in control of permanent magnet synchronous motors (PMSM) where the rotor position information is required. The cost of mechanical sensors and the difficulty to incorporate them make it necessary to avoid their uses and to study the mechanical Sensorless control. The idea behind such methods is to extract the motor position and speed information in functions of the terminal quantities from the motor equations. There are many methods which vary in principle and observer structure. In this paper some most promising methods are classified for different application conditions.