| Steel rolling is an important part of the metallurgical industry,and the thickness gauge is the core equipment of thickness control system in steel rolling production line.X-ray thickness gauge with high precision,adjustable power,high signal-noise ratio and fast response gradually become the first choice for steel thickness measurement.There are some shortcomings such as low precision and imperfect function in domestic X-ray thickness gauges.Therefore,the X-ray thickness gauge used in our country most of the equipment imported and the maintenance work brings great inconvenience,and monitoring management interface is not suitable for the Chinese operation habit,adding a lot of trouble to the production site.Therefore,the key technology of online measurement of X-ray thickness gauge of rolling mill is studied deeply,which provides theoretical guidance for the development of X-ray online thickness measurement system with high precision,good stability and system function with independent intellectual property rights.Firstly,the calibration process of X-ray thickness gauge is developed based on the working principle of X-ray thickness gauge and the actual situation of rolling steel production line.The calibration model of attenuation coefficient polynomial curve based on the analysis of the characteristics of the commonly used general polynomial fitting model,the effects of two calibration models are compared with experimental data,the results show that the new model is more accurate and adaptable than the ordinary polynomial fitting model.At the same time,the influence of the source voltage on the measurement accuracy and sensitivity is discussed,furthermore,the basis of setting the optimal source voltage for different thickness steel plates is given.Secondly,the influence of the variation of the source energy,the relative position of the strip and the thickness gauge,and the difference of the alloy composition on the measurement accuracy of the thickness gauge are analyzed,and the corresponding compensation method was proposed,and the compensation effect is verified by experiments.In addition,the comprehensive compensation model is proposed for the polynomial model and the attenuation coefficient polynomial model respectively.It provides an effective solution for the compensation of the thickness error of the actual production line,also lays the foundation for the error compensation strategy.Thirdly,according to the characteristics of steel rolling production line,combined with X-ray thickness measurement system function and technical indicators,the general scheme of distributed thickness measurement system based on industrial computer,PLC and Profibus-DP fieldbus is proposed.And the main hardware of the C frame,PLC master station and slave station were designed in detail.On this basis,STEP7 and LABVIEW are used as the platform to develop PLC control software and server monitoring software,the seamless connection between X ray thickness gauge and steel thickness control system is realized.Finally,According to the national "X ray thickness gauge verification regulation"(JJG480-2007),the repeatability,indication error and drift performance of the X ray thickness measurement system were tested,meeting the national standard.In addition,the resolution and sensitivity are also analyzed and evaluated to meet the design requirements.The X-ray thickness measurement system developed runs well under laboratory conditions.At present,it is ready to be put into trial operation in the steel rolling production line.The results of this study laid a solid foundation for the subsequent research and development of lateral thickness distribution measurement system. |
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