Zinc coating thickness control method and system based on time-varying delay deviation correction technology

Abstract

The invention provides a zinc coating thickness control method and system based on a time-varying delay deviation correction technology. Firstly, a data modeling method is adopted to model the coating thickness, the influences of production line speed, air knife pressure, knife distances, height and other factors on the coating thickness are predicted, and feedback control is conducted on controlled quantity according to a model predicted value to eliminate the influence of external disturbance on the coating thickness. Meanwhile, according to the characteristics of the galvanization production process, the delay time of measurement of a thickness gauge is accurately calculated, and based on the delay time, the current model predicted value is corrected by adopting a thickness gauge measured value and model predicted value information which are matched with each other to effectively solve the problem that feedback of measurement information is delayed due to large system time variation. In addition, the difference value between discrete inspection test analytical data and an online thickness gauge thickness measured value is introduced to correct a set value of a control objective of the coating thickness, and steady state residual errors of closed-loop control are reduced. The objectives that fluctuation of coating thickness is reduced, the control precision and the pass percent are improved, and excessive zinc consumption is reduced are achieved.

Description

technical field [0001] The invention relates to the field of automatic control of cold-rolled galvanizing process, in particular to a zinc layer thickness control method and system based on variable time-delay deviation correction technology. Background technique [0002] Galvanized products are widely used in construction, home appliances, automobiles and other industries because of their good corrosion resistance. They are widely used steel products in the production and consumption fields of our country. An important technical index to measure the quality of galvanized products is the thickness of the coating, which must meet the product specifications to ensure the corrosion resistance of the product; at the same time, due to the large pure lag and low model accuracy when the galvanizing process exists , environmental interference and other characteristics, the coating thickness of galvanized products fluctuates greatly, iron and steel enterprises often adopt the method ...

AI Technical Summary

Problems solved by technology

Due to process design and production line planning, etc., the installation position of the thickness gauge is far away from the air knife, resulting in a large measurement hysteresis from the application of the control amount at the air knife to the change of the coating thickness response detected by the thickness gauge.

At the same time, in the actual galvanizing production, the speed of the production line changes at any time, resulting in a time-varying delay in the measurement

The time-varying and large lag characteristics of galvanizing production increase the difficulty of thickness control in galvanizing production, which will lead to a large overshoot and long adjustment time of the control system

[0005] 2) It is difficult for the galvanizing production process model to accurately reflect the input-output relationship of the real system in real time

First of all, the mechanism of the galvanizing production process involves complex physical processes such as aerodynamics and laminar flow theory. The input variables are coupled with each other, and there is a strong nonlinear relationship between the input and output variables. or black-box modeling methods are difficult to establish a completely accurate production model

At the same time, there are many random disturbance factors in the galvanizing production process, such as production line speed, changes in zinc liquid composition and temperature, annealing furnace temperature changes, plate shape changes, air knife air pressure fluctuations, etc., which will affect the thickness of the coating. The fluctuation of the environment will lead to changes in the characteristics of the production system, which will cause a mismatch between the original model and the real system, and affect the control effect

[0006] 3) There is a deviation between the measured value of the thickness gauge and the test value

However, the system uses the sensitivity method (local linearization model) to calculate the control quantity, and there is a certain deviation between the model and the real system itself, and the model cannot be corrected online. Therefore, the system has poor adaptability to changes in the working conditions of the production system.

In addition, due to the difference between the installation and maintenance environment and the theoretical design conditions, the measurement data of the thickness gauge is not accurate enough, and the above method lacks an effective solution

In summary, although the current closed-loop control system of coating thickness in China has introduced certain mechanisms to overcome the large hysteresis characteristics of the system, these methods are affected by factors such as model accuracy, random disturbances, changes in working conditions, and large measurement deviations of thickness gauges. , the control effect is not ideal

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