Visual measurement of valve opening area with improved subpixel edge location

Abstract

The opening area error of the gas valve is mainly caused by machining, assembling errors and transmission clearances. Accurate measurement of the opening area is important for the production quality inspection of gas valves. This paper proposes a novel solution with a specific measurement system. Due to the reflective effect of the valve surface, the valve opening’s saliency is enhanced by the combination of top lighting and camera exposure. Then, a partial image is used to extract the single closed edge of the valve opening. To obtain the precise edge position, a subpixel location based on the rotating area effect is applied. Finally, the area computation based on the minimum circumscribed circle and the maximum inner circle of the edge is provided. The experiment results prove the system reliability, and the general significances of the proposed algorithms.