Research On Coaxiality Detection Method Of Continuous Liquid Steel Temperature Sensors Of The Black Body Cavity Type And DSP Implementation

The new continuous liquid steel temperature sensor of the black body cavity type solves the problem that the traditional continuous liquid steel temperature sensors of the black body cavity type has a slower temperature response speed,and can hardly meet the requirements of rapid temperature response in the occasions such as continuous casting,pouring,tundish changing and refining.However,in actual use,it has been found that some new continuous liquid steel temperature sensors of the black body cavity type still have a problem of response speed lag.Experiments and tests show that the primary cause of the response lag for the new continuous liquid steel temperature sensor of the black body cavity type is that the ceramic metal tube of the sensor and the sensor body do not have shaft alignment.Therefore,the position detected by the infrared sensor moves up along the cavity wall,and the area with lower heat transfer rate is also included,resulting in a lower response speed than the speed when the detector is aligned with the bottom of the cavity.For the problem of shaft misalignment between the new continuous liquid steel temperature sensor of the black body cavity type and ceramic metal tube,this thesis proposes a coaxiality detection method for the continuous liquid steel temperature sensor of the black body cavity type with error compensation on a basis of a large number of experiments.The following researches are carried out:(1)The coaxiality detection model of the new continuous liquid steel temperature sensor of the black body cavity type is established and the coaxiality detection method is improved from the layer of measurement principles.By analyzing the features of the maximum radiance brightness point on the inner surface of the hemisphere,three characteristics of the inner surface radiance brightness of the ideal diffuse reflection hemisphere are obtained;by analyzing the relationship between the measured deflection angle and the maximum radiance brightness point on the inner surface of the hemisphere,the derived formula for the deflection angle and the maximum radiance brightness point on the inner surface of the hemisphere is reached;improve the coaxiality detection method of the new continuous liquid steel temperature sensor of the black body cavity type to make the improved method suitable for running on the DSP.(2)The design of the coaxiality detection device for the new continuous liquid steel temperature sensor of the black body cavity type is completed.The thesis analyzes the characteristics of built-in machine vision detection technology and puts forwards that the high-performance digital signal processing chip TMS320DM642 produced by Texas Instruments is used as the core processor.The peripheral circuit for TMS320DM642 is engineered,and the design of the coaxiality detection device for the new continuous liquid steel temperature sensor of the black body cavity type based on DSP is realized.(3)The coaxiality detection method for the new continuous liquid steel temperature sensor of the black body cavity type based on DSP digital image processing is realized.The revision-based image differential denoising method is adopted to achieve the image background noise filtering and target area positioning.Common denoising methods are studied,and the image discrete point noise is compared with and then removed.The gray scale centroid method is improved to achieve the accurate positioning of the light spot center;the error compensation method is proposed to solve the problem that the ceramic metal tube target is not a standard hemispherical surface and to improve the detection accuracy of the detection device.(4)The influence factors and error causes for the coaxiality detection of new continuous liquid steel temperature sensors of the black body cavity type are analyzed here.The correctness of the detection principles and the accuracy of the detection methods in this thesis are verified by experiments.The coaxiality measurement phenomena or results of new continuous liquid steel temperature sensors of the black body cavity type with different lengths,materials and radii are compared and analyzed in these experiments.The conclusion:new continuous liquid steel temperature sensors of the black body cavity type with different lengths,materials and radii have different influences on the measurement accuracy.The common error causes for the coaxiality detection accuracy of new continuous liquid steel temperature sensors of the black body cavity type are analyzed and the effects of external illumination,target defect and spot on the detection accuracy are explored.The coaxiality detection method proposed in this thesis realizes that the accuracy of the maximum error in the 80 deflection angle is less than 0.5°,and has achieved good detection results.