Key Technology Research Of Point Meter Detection Based On Computer Vision

Precise pointer meter is used largely because it is easy to use and reading intuitively with simple structure and cost effective. For safety and quality of the production the pointer meter must be regular verification, to ensure its practical precision. Because precise pointer meter reading needs special requirements, so its artificial verification is time-consuming and easy to produce error and affecting the calibration accuracy. If the readings automatic identification of pointer meter can be implemented within the allowed error, Pointer Meter Automatic Verification System (PMAVS) will greatly improve the verification efficiency and verification precision of pointer meter at metrology organizations. So Implementation of the pointer meter readings accurate automatic identification has important theoretical significance and application value.The research of pointer meter reading automatic recognition has some definite development for several years, low precision pointer meter readings automatic recognition has been realized; Precise Pointer Meter (not less than0.5) Automatic Recognition System isn’t currently found. Every year tens of thousands of precise pointer meter need verification. Because the big scale area, the many scale lines, high accuracy of reading recognition and the computational complexity of the image processing, it is not implemented that the readings automatic identification of precise pointer meter, so all verification of them must be done by artificial work.This dissertation object of study is milliampere precise pointer meter of0.5accuracy grade. The main studied problems of this dissertation include:lighting imaging system of pointer meter, image preprocessing, scale pointer image segmentation, scale line feature extraction, scale line detection and fitting, reading recognition method and error correction. Those were studied systematically to solve the problem of reading recognition speed and accuracy. The main research results and innovation points of this dissertation can be expressed as follows:1. According to the physical characteristics and error requirements of precise pointer meter, it is builded the side projection imaging system with square shadowless light, to solve the problem of image acquisition in the black box only. This dissertation proposes a fast method to obtain the reading area image of meter, providing a basis for fast identification of reading.2. According to brightness distribution characteristics of the scale line image in the reading area, the denoising experiment of reading area image is filtered by both filtering algorithms. A filtering algorithm is the coupling of shock filtering and complex diffusion filter algorithm. Another filter algorithm is the manifolds filtering algorithm based on heat equation theory. The denoising experiment results of the former are superior to the latter in computing speed and denoising effect. The former can significantly enhance the image of scale line image characteristics, providing a basis for the accurate extraction of scale lines feature image.3. According to the characteristics of the scale lines image, it is proposed the image segmentation algorithm based on Snake model and variational level set for the scale lines image experiment simulation. Both methods have their advantages and disadvantages which can be chosen depending on your needs. The segmentation accuracy of former method is higher, but needs artificial participation. The latter without artificial participation, can rapidly and accurately extract image multiple scale lines characteristics. The latter method is suitable for long and thin kind of multi-objective extraction.4. Analyzed the structure characteristics of Precise Pointer Meter, the method of the monocular imaging model was proposed to correct the viewpoint error, and the simulation experimental results have obtain the desired accuracy requirements. Building the binocular imaging model of precise pointer meter, the viewpoint error correction formula is deduced, providing a theoretical basis foundation in order to realize precise pointer meter automatic reading recognition.5. A new reading recognition methods based on virtual dial was proposed, combining with the scale line fitting method based on the center of scale to eliminate the eccentricity error. The method is given to reduce the nonlinear error of scale line distribution, improving the reading recognition accuracy.Based on the research results, this dissertation gives the requirements of the precise pointer meter reading automatic identification system, and has carried on the simulation experiment, obtaining the good results and providing a theoretical basis foundation to develop precise pointer meter automatic verification system. This dissertation has a certain practical value.