Dynamically Optimized BLDCM Commutation Method Based on Rotor Magnetic Potential Real-Time Space-Symmetry Regulation

High-precision commutation is a key factor for ensuring the maximum torque per ampere of brushless DC motor (BLDCM). In order to compensate the commutation error for position sensorless BLDCM, a commutation dynamically optimized strategy is proposed by employing a flux linkage acquisition circuit (FLAC) along with a novel model-free derivative-based compensator (MDC). First, based on the rotor magnetic potential space-symmetry analysis, it is pointed out that the per commutation-cycle integral of the rectified voltage from DC-link midpoint to virtual neutral point reaches the minimum value under the condition of accurate commutation. Then, the FLAC is designed to obtain the voltage integral which is actually a combination of three-phase flux linkage variation. Finally, the real-time commutation optimization algorithm of MDC is introduced to compensate the commutation error with the aim of the voltage integral approaching minimum value. Experiment results from a magnetically suspended control moment gyroscope verify the proposed method.