Adaptive fourier series speed controller for permanent magnet synchronous motor and brushless dc motor

Abstract

Permanent magnet motors provide the highest power density and highest efficiency among all types of electric motors. For machine tool components and fast dynamic positioning systems the PMSM motors are commonly used. On the other hand, the BLDC motor delivers a higher torque to size ratio compared to DC motors, making it suitable for applications where weight and space are important factors. The construction of PMSM and BLDC motors is similar. However, they require completely different control approach, (Field Oriented Control for PMSM and Trapezoidal Control for BLDC). In this paper a new adaptive controller for PMSM and BLDC motors is proposed. For this controller a trapezoidal control is implemented and the torque ripple (due to non-trapezoidal back-EMF), is reduced using a Fourier series approach. The proposed controller was implemented experimentally and the results confirm it is effective to reduce the effect of internal torque ripple as well as the speed ripple produced by external periodic torque disturbances applied to the PMSM. Using the Adaptive Fourier Series Controller, the reduction on speed ripple was 2.7% of nominal speed when the first four terms of Fourier series were used, while the standard Field Oriented Control produced a speed ripple of 112% of the nominal angular speed.