Fourier-Series-Based Phase Delay Compensation of Brushless DC Motor Systems

Abstract

Brushless direct-current (BLDC) motors are being regarded as a standard of actuation methods for precise and heavy-duty applications, such as robots and vehicles. To improve the efficiency and torque performance of the BLDC motors, various design parameters (e.g., the magnetic flux density, core material, etc.) have been investigated. Phase delay compensation (PDC), also often called phase advance angle control, is also an attractive method that improves the actuation efficiency of BLDC motors without any mechanical modification of the motors. Due to the inductance of the BLDC motor windings, the magnetic flux of a rotor and that of a stator are not generated in phase, which causes a phase delay in magnetization of the coil. Due to this phenomenon, the efficiency of the BLDC motor is remarkably decreased, in particular at a high speed, and the PDC can be applied to compensate for this phase delay. In this paper, Fourier-series-based PDC is proposed to improve the efficiency of the motor; the phase delay angle is calculated based on the dynamic model of the motor windings and its Fourier series. The proposed Fourier-series-based PDC is realized by designing an inverter circuit that switches the phase voltages according to the proposed algorithm. The performance of PDC is verified at experiments in terms of not only T-N curve but also control performance. According to the experimental results, PDC improves output torque, efficiency, and control performance.