Position control based on image processing

In this study, image processing based on-off control of a double-acting pneumatic cylinder was realized. Motions of the cylinder was observed through the medium of a USB webcam and photographed periodically. Digital images initially transferred to a computer were converted into gray scale images. Subsequently, the background and cylinder were separated through the thresholding process. Position information was estimated from pixel numbers due to the fact that the webcam was fixed within the system. The relevant valve is switched on and off in according with the difference between the desired and actual position with on/off control algorithm. An user interface has been developed using Builder C++ programming language and the valve has been driven via the parallel port of computer.