Steady state Kalman filtering for sensorless control of hybrid stepper motors

Extended Kalman filtering techniques have been successfully used as sensorless control schemes on many different types of synchronous motors. One big disadvantage of the extended Kalman filtering technique is the large computational cost. Even with today´s powerful DSPs, it is difficult to achieve effective real-time implementations. It is especially problematic for high speed motors or motors with many pole pairs such as hybrid stepper motors. In this article, it is shown how a steady-state version of the Kalman filter can be used to calculate the rotor position and speed for a hybrid stepper motor. By using a steady-state Kalman filter the computational effort can be drastically reduced. The proposed method is verified by a closed loop simulation of a hybrid stepper motor with additional current and speed regulators.