Sensorless Low Speed PMSM Motor Control with Cogging Torque Compensation

The paper presents sensorless control of a low-speed permanent magnet synchronous machine with use of modified state observer. An overview of the PMSM motor used in the research setup was presented. The problem of drive torque ripple, resulting mainly from the occurrence of a significant cogging torque, was discussed. A solution compensating the torque ripple of the PMSM motor was proposed. A start-up procedure of the speed control system, allowing to run the drive system without speed and position sensors, was prepared. The field-oriented control with PI controllers of stator currents in the dq axes was implemented. The equations of a new, simplified version of the Krzeminski observer were presented. The observer has simpler structure of the gains, thus it is less computationally-intensive and easier to tune. The experimental results confirming the correct operation of the drive system were shown.