| China, a manufacturing power, the capacity of design and manufacture of high grade heat treatment equipment was poor, nearly depended on imports, and the traditional production model was so extensive that the performance and operating life of mechanical parts was far worse than similar foreign products, meanwhile, for its energy consumption, pollution and low benefit, it hindered the healthy development of our country’s industry.At present, Chinese heat treatment enterprises mainly applied the thermocouple to measure the temperature of heat treating accessory inside the furnace, while the thermocouple was cheap and measurement result was precisely, but thermocouple as a typical contact temperature measurement, its shortcomings were the following five points, firstly, dued to contacting with the measured object or medium directly, put forward higher requirements on the stability of the measuring instrument and the life and property of temperature sensing element in the harsh environment, secondly, the contact itself also had influences on the temperature field distribution of measured object or medium, thus increasing the error of temperature measurement, thirdly, compared with non-contact temperature measurement, the performance of dynamic response was poor and the inertia of temperature measurement was large, fourthly, contact temperature was measuring the temperature of one point temperature field or medium, not to reflect the distribution of temperature field, the induction heating and microwave heating could not get accurate temperature of heating workpiece, fifthly, contact temperature measurement was inconvenient to install and maintain, was bad to the industrial intelligent control.Although the optical pyrometer and infrared temperature measurement instrument could be used to measure the temperature of the heated treatment, but the measurement range of these kinds of instruments were limited and the prices were much higher, at the same time, the relatively harsh environment of industrial production would also affect the measurement accuracy. In recent years, many domestic and abroad scholars researched non contact measurement of high temperature which based on digital image processing techniques, but the system was complex with poorly anti-interference ability, was still at the experimental research stage.As a result, today’s heat treatment industry needed to develop a heat treatment measurement equipment which could work on real-time, with high precision, good dynamic response, low thermal inertia, high grade automation and strong anti-jamming capability, it had important significance to further improve the heating efficiency, optimize the heating process, improve the production quality, reduce energy conservation and emissions, protect environment, improve workers’operating conditions in the enterprises.Non-contact high temperature measurement technology was based on the CCD image sensor, integrated application of the photoelectric image detection technology, digital image processing technology and temperature measuring of thermal radiation theory. The digital image processing technology had many advantages, firstly, its good reproducibility, which could keep the whole image information in order to reproduce the image, secondly, the widely application range, the image signals caould be derived from a variety of channels, for the image information from different sources, as long as chose corresponding image acquisition method and sensor, then the digital image processing technology could be used for processing all images, thirdly, processing of high accuracy, with the development of computer technology and mathematics, the accuracy of digital image processing could be assured by changing relevant parameters of processing procedures or algorithms, fourthly, high flexibility, digital image processing covered a variety of image processing, when the algorithm using mathematical formulas or logical operation relation to express, the digital image processing technology could realize. This method had all the advantages of non-contact measurement, responsed rapidly, which did not destroy the measured temperature field, large range of temperature measurement, and so on.Carbon steel production accounted for about80%of the total steel production, was the mainly metal materials, with applying this technology, this paper researched on non-contact measuring system of carbon steel heat treatment temperature.This paper mainly included the following contents.(1) The overall design of temperature measurement systemBased on a review of relevant literatures and technical datas on temperature measurement techniques based on digital image processing technology at home and abroad.Masteredthe measurement principle, made comparative analysis of temperature measurement methods, found the relevant existing problems in the field, made the technological developments direction clear, combined with the object of study, selected the appropriate temperature measurement methods, and designed a measurement system, including data collection and storage, data processing and feature values extraction to establish temperature measurement model and temperature measurement software platform.(2) Calibration experiment design and temperature calculation algorithm designCalibration experiment was based on deep understanding of the principles of thermal radiation thermometry, designed a set experiment to gain the target images with accurate parameters corresponding to the temperature, according to the relationship between the distribution of the feature values extracted from target images and temperatures, selected the appropriate feature values to calibrate temperature measurement system, the experiment directly determined the measurement precision and accuracy of the temperature measurement system.The design of temperature measurement algorithm was based on currently non-linear fitting method which used widely and combined with the data structure of this paper. Based on the least square method and BP neural network to design algorithm, the method of least squares method adopting automatic search for the best order to obtain the best fitting results, BP neural network by setting appropriate network parameters to ensure accuracy and operation speed of the network, in this paper the calculate results and error analysis has been given in figures to explain in detail.Because of the existence of good monotonic relationship between the distribution of the whole gray target feature values and temperature, so chose the relationship to calibrate the temperature measurement system, used the interpolation algorithm to improve the resolution of the temperature measurement system, so that the algorithm could be applied to real-time measurement.(3) The design and commissioning of temperature measurement software platform based on MATLABBased on MATLAB software platform, applied GUI programming language, designed a temperature measurement software system, the system could achieve the images of the targets, processed on real-time, temperature measurement on real-time, error analysis, and the image was automatically collected in accordance with the saving time shot into the appropriate directory for authentication on the subsequent. The software platform has been tested and met the design requirements fully.Overall, the innovation of this thesis could be summarized as the following three points.Firstly, combined with thermal radiation theory, the principle of photoelectric imaging, digital image processing, scientific computing methods and other aspects of knowledge, to realize the non-contact measurement of the carbon steel heat treatment temperature, and the measurement accuracy met with industrial application. It was a new technical solution for industrial automation and precise control of heat treatment, explored the practical and effective to improve our level of heat treatment technology, energy-saving emission reduction, improve the working environment of the staff.Secondly,based on the principle of radiation temperature measurement, combined with colorimetric method and the three color method, a new temperature measurement system calibration method was put forward, the method was not only simple and high accuracy, but also simplified the method of eigenvalue extraction and image processing.Thirdly, used the GUI graphical interface programming, designed a set of interactive temperature measurement platform, the platform was beautiful and simplicity,meanwhile, powerful function, convenient operation, and the user can secondary develop according to their actual needs. |
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