Encoder-less field-oriented control of permanent magnet synchronous motor by using a full order adaptive state observer

摘要

This paper proposes a full order adaptive state observer, for the field-oriented control of a permanent magnet synchronous motor (PMSM), without using a speed sensor. The observer is designed in the estimated field-synchronous coordinate system. The rotor speed is treated as an unknown parameter. The adaptive law for speed is derived by using Lyapunov's stability theorem. Since control algorithms and models are processed in micro computers, the proposed observer has been discretised by Euler's method. To make the observer dynamically faster than the motor dynamics, observer poles are fixed proportionally to those of the motor by using pole placement technique. The simplifying assumptions used to discretise the observer, along with the stator current harmonics, introduce ripples in the estimated rotor speed. To mitigate this effect, various counter-measures are explored. The validity of proposed scheme is verified through MATLAB Simulink.