A DSC - Based field oriented control of SPMSM to mitigate practical difficulties with low resolution sxIncremental encoder

Practical considerations for implementing Field Oriented Control (FOC) of Surface mounted Permanent Magnet Synchronous Motor (SPMSM) with a low resolution incremental encoder are discussed. The performance of FOC heavily depends on the accuracy of rotor position measurement. To minimize the development cost, high resolution incremental encoders or absolute encoders are avoided. The error in rotor position measurement is reflected as ripples in dq-axis stator current components. Absolute rotor position at startup is not known resulting in wrong interpretation of rotor d-axis and q-axis orientation. This paper describes the implementation of FOC using STMicroelectronics make Digital Signal Controller (DSC), STM32F407 with 168MHz core speed. Initial rotor alignment and accurate rotor position measurement along with step by step debugging process is discussed. Hardware results are presented for the verification of the same.