Improved Sliding-Mode Observer for PMSM Sensorless Indirect Field-Oriented Control

In this article, the sensorless fast bidirectional start-up and speed regulation issues of permanent magnet synchronous motors (PMSMs) are addressed in the framework of indirect field-oriented control (IFOC). The proposed sensorless control scheme consists of a reduced-order adaptive speed observer and an alignment controller. As the input of the speed observer and the corrective term of the alignment controller, a hybrid terminal sliding-mode flux observer (HTSMO) is developed. Different from conventional flux observers (CFOs), the proposed one removes the assumptions about flux measurement or pure integration of the stator flux model, and a prior knowledge of load torque is also not required. Under the fast flux estimation and tracking, the alignment error can be corrected, and the rotor speed can synchronize with the electrical one. The stability analysis and the parameter tuning principles are also presented in detail. A set of PMSM control experiments driven by the ST digital signal processor (STM32F429) confirms the quick response and robustness of the proposed scheme.