A Novel Fast-Filtering Method for Rotational Speed of the BLDC Motor Drive Applied to Valve Actuator

A novel fast-filtering method for rotational speed measurements, applied to the brushless direct current motor drives, is proposed and tested in the paper. The spatial misalignment of the sensor for rotor position (Hall sensor), as well as its inhomogeneous magnetization, causes the measured rotational speed to jitter around its average value even when the rotor rotates at constant speed. The proposed fast-filtering algorithm is based on the assumption that the speed jitter is periodic, since the measured speed pattern is repeated after each one revolution of the rotor. The algorithm is tested on a valve actuator. The experimental results show that the speed jitter is substantially reduced, whereas fast reaction of the speed control loop is preserved in contrast with the classical filtering methods.