A Zero-Crossing Detection System Based on FPGA to Measure the Angular Vibrations of Rotating Shafts

In this paper, the efficient implementation of a reliable measurement device to measure the angular velocity vibrations of rotating shafts is discussed. The solution is particularly suitable to be fit in measurement embedded systems equipped with field-programmable gate arrays (FPGAs). The proposed measurement method is analyzed from a theoretical point of view, focusing the study on the frequency response of the technique. On the basis of the theoretical results, a reliable and low-complexity design of the measurement device has been proposed. In the adopted solution, the high clock rates of FPGAs are exploited to increase the accuracy of the zero-crossing times estimation, for a given A/D acquisition frequency, using an upsampling approach. The experimental results confirm the validity of the technique. The upsampling method allows an increase of the measurement accuracy and an improvement of about 10 dB for the output signal-to-noise ratio over a wide range of vibration frequencies.