A novel arithmetic based on coordinate transformation for sensorless brushless DC motor drives

This paper presents a novel method for sensorless BLDC motor drives, which is based on coordinate transformation, in order to compensate the rotor position detection error caused by the first-order low-pass filter over wide speed ranges. Two coordinate systems are defined, which are named as `a´ and `b´. For compensating the error, the angle beta, which is between `b´ coordinate system and `a´ coordinate system, is controlled in real time, and the zero-crossing timing of reconstructed position signal, which is the projection on `b´ coordinate system from `a´ coordinate system, is just the phase commutation timing. The rotor position detection error is analyzed and experimental results verify the analysis and demonstrate advantages of the new arithmetic.