The Application of the Butterworth Low-Pass Digital Filter on Experimental Data Processing

The piston’s displacement of the pneumatic cylinder is measured through a displacement sensor, and then the speed and acceleration of the piston are obtained by a differential method, due to the differential amplification of the displacement-time curve of the interference signals, resulting in the speed-time curve of the interference signal intensified. Hence we designed the Butterworth low-pass digital filter using MATLAB, and to compare the effect of the speed-time curve smoothing, we adopted the other common data processing method of the moving average as comparison object. The results show that the speed-time curve becomes smoother when adopting the five-point moving average method, but the curve moves forward overall, the error is larger. However, the filtered velocity curve is smooth and without distortion, which shows that the design using the low-pass digital Butterworth filter processing speed curve is valid.