Research on Angular Displacement Sensing Method of Linear Frequency-Modulated Eddy Current Time Grating

The sensing signals of electromagnetic displacement sensors, represented by the current angular displacement eddy current time grating, are prone to be interfered by non-ideal factors such as metal chips and oil stains under harsh working conditions such as high-speed cutting and heavy-duty mechanical transmission, resulting in a significant decrease in signal-to-noise ratio. In this paper, a new eddy current time grating displacement sensing method is proposed. This method takes linear frequency modulation as the main feature of sensing signal and matched filtering as the main means to improve signal-to-noise ratio. By modulating the angular displacement information to the parameters of the linear frequency modulation waveform, and demodulating it with matched filtering at the receiving end. The noise interference inconsistent with the frequency modulation law is effectively suppressed, and thereby the signal-to-noise ratio is greatly improved. The simulation results show that when the carrier frequency is 5 MHz and the pulse width is 8 μs, the signal-to-noise ratio of the improved system is 75 dB higher than that of the current eddy current time grating sensor under the same noise environment. The improved system significantly enhances the anti-interference ability of displacement measurement.