Independent thesis Advanced level (professional degree), 20 credits / 30 HE credits
A permanent magnet synchronous motor is traditionally controlled from measured
values of the angular velocity and position of the rotor. However, there is a wish
from SAAB Avitronics to investigate the possibility of estimating this angular
velocity and position from the current measurements. The rotating rotor will
affect the currents in the motor’s stator depending on the rotor’s angular velocity,
and the observer estimates the angular velocity and angular position from this
There are several methods proposed in the article database IEEE Xplore to
observe this angular velocity and angular position. The methods of observation
chosen for study in this thesis are the extended Kalman filter and a phase locked
loop algorithm based on the back electro motive force augmented by an injection
method at low velocities.
The extended Kalman filter was also programmed to be run on a digital signal
processor in SAAB Avitronics’ developing hardware. The extended Kalman filter
performs well in simulations and shows promise in hardware implementation. The
algorithm for hardware implementation suffers from poor resolution in calculations
involving the covariance matrices of the Kalman filter due to the use of 16-bit
integers, yielding an observer that only functions in certain conditions.
As simulations with 32-bit integer algorithm performs well it is likely that a 32-
bit implementation of the extended Kalman filter would perform well on a motor,
making sensorless control possible in a wide range of operations.
2009. , 74 p.