Design of Current and Back Electromotive Force Observers for Ironless-stator Permanent Magnet Brushless DC Motor Dual-Stage Drive

Precise information on the current and back electromotive force is required to improve a brushless DC motor’s operational performance. For the dual-stage drive, a back electromotive force observer and a current observer corrected by the commutation signal based on the extended state observer were created. The properties of the classic nonlinear error gain function were theoretically investigated using mathematical analysis. By thoroughly researching the observer’s structure, a methodology for confirming optimal parameters through parameter traversal in experiments based on a digital control platform was developed. The ideal observer gain parameters were then found under various operating situations, such that the observer parameters match the constantly changing system at any moment. The experimental findings demonstrate that the output of the current observer and the back electromotive force observer may converge within the motor’s primary operating conditions of 2000 rpm to 3000 rpm, allowing the current, disturbance, and back electromotive force to be tracked efficiently. This work introduces an observation technique for the physical quantities of an ironless-stator permanent magnet brushless DC motor powered by a two-stage drive, as well as the optimization of extended state observer parameters for this architecture.