An automatic reading method of pointer instruments
Yifan Ma, Qi Jiang, Wang Junjie, Tian Guohui · 2017
Aiming at the problem that the reading speed of pointer instruments is slow and the precision is low, this paper proposes a new automatic reading algorithm. The paper improves the algorithm in instrument center recognition, pointer recognition and 0 scale line recognition. First, round-degree is used to recognize the instrument center. Then the algorithm removes the interferential images outside the pointer area through the polar angle frequency distribution histogram and uses the improved least square method to fit the pointer line. It overcomes the problem that the fitted line is off the instrument center. Next, the proposed method removes the interferential images around the 0 scale line by the polar radius frequency distribution histogram and uses the improved least square method to recognize the 0 scale line. It solves the problem that Hough line transform recognizes the short line under the influence of interferential images difficultly. Finally, the method calculates the reading according to the relationship between instrument scales and pointer angles. Experimental results prove that the algorithm is fast and accurate.