Design of Motor Shaft Power Meter Based on Phase Detection Using Improved All Phase FFT

This paper presents a measurement scheme of the motor shaft power based on the phase detection using the improved all phase fast Fourier transform (APFFT). This method can measure the phase difference and frequency of the output signals from the torque-speed sensor connected to the motor, which are proportional to the torque and revolving speed, respectively. A signal processing circuit is proposed to stabilize the amplitude of the output signals from the torquespeed sensor which fluctuates with the change of operating states of the motor. In addition, STM32 single-chip computer is applied to sample the output signals, and an improved APFFT method is performed on this microprocessor, which can detect the phase with a high measurement accuracy. It is proved that the improved APFFT method is immune to the interference of the harmonic and direct current noise, and it has a high accuracy when the Gaussian noise is not server. Experiment results are shown to prove the validity of the proposed scheme.