Hall-sensor signals filtering for improved operation of brushless DC motors

Brushless dc (BLDC) motors controlled by Hall-effect sensors are becoming widely available and used in a wide variety of applications. Such motors have been extensively researched in the literature under a common assumption that the Hall sensors are ideally placed 120 electrical degrees apart. However, sensor positioning may be quite inaccurate in low- to medium-precision motors leading to unsymmetrical operation of the inverter and motor phases, which increases the torque ripple and degrades the drive performance. To mitigate this phenomenon, an approach of filtering the Hall-sensor signals has been proposed. This paper extends the previous work and presents a very efficient digital implementation of several averaging and extrapolating filters that can be easily included into various BLDC motor-drive systems. The implemented prototype and experimental results demonstrate the effectiveness of the proposed approach by completely restoring the motor operation in steady state and transients.