Signal processing method for measurement of sub-period speed fluctuation

Abstract Sub-period speed fluctuations of the measuring unit for a photoelectric scanning measurement network can directly affect the accuracy of the entire system. This study proposes a signal processing method for the measurement of subtle sub-period rotation speed fluctuation that includes two corresponding processing methods for different speed ranges. For the low-speed range, the specific steps included the calibration of the encoder gratings and relative measurement of the rotation speed. For the high-speed range, the corresponding signal processing method utilised the average speed, which represents the instantaneous speed at the middle moment. The sub-period speed fluctuation is very subtle for precise motion control, accounting for only 0.001% of the speed. Conventional methods cannot acquire the actual sub-period speed fluctuation due to the eccentricity error and scale error. However, the proposed method can measure the subtle sub-period speed fluctuation by filtering the interferences of the eccentricity and scale errors. The proposed method does not require any additional hardware and provides high accuracy.