An automatic control method for zinc layer thickness in a continuous hot galvanizing zinc line

Abstract

The invention provides an automatic control method for zinc layer thickness in a continuous hot galvanizing zinc line. According to the method, a self-adaptive controller of a BP neural network structure and a delay estimation strategy are adopted to realize closed-loop precise control of a plating layer; a sampling thickness deviation of the plating layer is adopted as inputs of a self-adaptive control model of the BP neural network structure; and finally reasonable outputs are generated through data treatment of two groups of weighting factors [Delta]wij(n) and [Delta]hj(n) in the self-adaptive control model, so that air-knife pressure can be adjusted in time; and finally, the deviation between a preset value of the thickness of the plating layer and an actual sampling value becomes smaller and smaller. A learning algorithm of the weighting factors refreshes the weighting factors continuously by the smallest deviation between the preset value of the thickness of the plating layer and a measured value as a principle, and finally the results of self-adaptive adjustment of the two groups of the weighting factors make deviation between the preset value of the thickness of the plating layer and the actual sampling value tend to zero. The method can greatly reduce excessive consumption of zinc, improves surface quality of the hot galvanizing zinc plating layer, and increases added value of products.

Description

Technical field [0001] The invention belongs to the field of rolling process automation, and is suitable for hot-dip galvanizing line galvanizing process and coating control technology, especially for processing the strong nonlinearity and time-varying hysteresis of the zinc layer thickness control process. Background technique [0002] At present, the major hot-dip galvanizing process manufacturers in the world have formed a set of their own coating control model based on the summary of production experience. The main feature of the control model is to determine the current detected occurrence according to current production conditions and control target requirements. Change the nature of the parameters, and then use the corresponding model to calculate the control parameter setting value. The model structure is almost the same. They are mainly based on adjusting the distance between the air knife and the strip and the pressure parameter of the air knife nozzle. The domestic hot...

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Problems solved by technology

[0004] 1) The relationship between coating thickness, air knife pressure and air knife distance cannot be expressed by a simple dynamic equation, so it is difficult to establish a model;

[0005] 2) Due to the constraints of production conditions, especially the influence of the high temperature of the zinc pot, the installation position of the coating thickness gauge is 140m away from the air knife, which has serious hysteresis characteristics, and ordinary PID control is helpless to this large lag problem. Can consider adopting advanced control implementation;

[0006] 3) In this system, the air knife air pressure adjustment is controlled by the variable frequency drive of the fan, which has strong nonlinearity;

[0007] 4) There are many factors affecting the coating thickness on site, including: strip speed, strip thickness, strip width, air knife angle, air knife height, etc. In addition, there are many interference factors, including: strip shape, strip Jitter, etc., have a great impact on its precise control

[0011] The process of coating thickness is a large pure lag process, and the lag time is uncertain. Factors such as strip speed, width, thickness and other process specifications affect the effect of air knife pressure, and position operations such as air knife gap, height, angle, etc. knife pressure effect

[0012] In the existing technology, the traditional PID control is still used in the zinc layer thickness closed-loop control method, but due to the serious nonlinear, time-varying, and large hysteresis phenomena of the control object, the traditional PID control including the extended PID control cannot meet the requirements Control effect

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