PLC implementation of a noise reduction sliding mode filter

Automatic control systems usually require filters to smooth feedback signals that contain various noises. On the other hand, most of industrial automatic control system apply programmable logic controller (PLC), which uses ladder diagram that represents the relationship between control process by using graphical symbols and blocks. This paper presents a method for implementing a parabolic sliding mode filter, of which discrete-time algorithm is described in a mathematical way, on PLC by using ladder diagram. The effectiveness of the presented method was experimentally validated with different types of input signals that were seriously corrupted by noise.