关键词: 油位计, 指针式仪表, 示数识别, 拍摄角度, 刻度定位

Abstract: In order to solve the problem that the reading recognition of pointer-type oil-level meter is easily affected by the change of shooting angle and illumination conditions，a new method for recognizing the readings based on ac-curate scale location was proposed by considering the characteristics of pointer in the industrial production． It only uses the scale and pointer to calculate the reading of meter． In this method，firstly the images of oil-level meter taken by the patrol robot was preprocessed; then all possible scale areas in the picture were recognized coarsely;and finally the scale was accurately located by fine recognition． In view of the problem that the traditional instru-ment recognition method is hard to solve the relationship between the center of the circle and the center line of the pointer is not certain to be established when the shooting angle is large，this paper adopted an improved method to select the center of the circle． This method is more suitable for the calculation under the influence of the shooting angle change，and can improve the reading accuracy． The experimental results show that the reading accuracy of the instrument obtained by this method is 99. 08% on average，and the algorithm is reliable and stable．

Key words: oil-level meter, pointer-type meter, reading recognition, shooting angle, scale localization