An Adaptive Filtering Method Applied to Constant/Variable Speed ​​Grating Signals

Abstract

The invention provides an adaptive filtering method applied to a constant-speed / variable-speed grating signal. A grating reading head makes constant-speed / variable-speed motion at a grating ruler to generate a frequency-variable grating signal when the frequency of the grating signal of the entire period is assumed to be constant; a high-speed A / D data acquisition device collects two paths of sine and cosine original grating signals in real time, the two paths of original grating signals pass through a zero-crossing comparator, and thus the signals are converted into two paths of orthogonal square wave signals with constant frequencies; with known high-speed pulses, interpolation counting is carried out between a rising edge and a falling edge of each orthogonal square wave signal, and then calculation is performed to obtain a corresponding grating signal fundamental frequency; and then according to the grating signal fundamental frequency, extraction is performed on the two paths of original grating signals by using an adaptive Vold-Kalman order filtering method to obtain a first-order low-frequency signal based on the fundamental frequency, and a high-frequency signal whose frequency is an integer multiple of the fundamental frequency is filtered. According to the invention, while the high-quality grating signal is restored, on-line real-time correction of the grating signal is performed, so that the dynamic measurement accuracy of the grating measurement system is improved.

Description

technical field [0001] The invention relates to the technical field of grating precision measurement, in particular to an adaptive filtering method applied to constant / variable speed grating signals. Background technique [0002] The grating measurement system takes the grating pitch of the scale grating as the measurement reference, and uses the principle of photoelectric scanning to convert the relative movement of the grating reading head and the scale grating into fringes of light and dark changes, that is, Moiré fringes; the photoelectric conversion device sensitive to light intensity converts the light and dark changes Moiré fringes are converted into periodic approximate sine-cosine electrical signals, denoted as S 0 (t), C 0 (t). Ideally, the grating signal obtained by the grating reading head should be two perfect orthogonal sinusoidal grating signals with no higher harmonics, zero DC drift, equal amplitude, and a phase difference of 90 degrees. However, there ar...

AI Technical Summary

Problems solved by technology

At present, the multi-reading head uniform filtering method is mainly used to suppress the high-order harmonics of the grating through the hardware system. The most extensive method, typical methods include neural network adaptive filtering method, Lissajous circular waveform reconstruction method, etc. Software suppression and elimination of high-order harmonics has the advantages of low cost and easy implementation, but its method is relatively complicated and real-time poor sex

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