Synthesis method for the modelling and robust control of coating weight at galvanizing process

Abstract

In this paper, we propose a new practical synthesis model for coating weight control and robust design method of feedback controller in galvanizing process. Firstly, we propose a new model, which combines both long term and short term model. Long term model has a good accuracy to predict the next distance and pressure of air knife for wide range of target coating weight, because it has the functions of classification, averaging and learning based on real measured data. Short term model has variational form based on linear change of inputs and outputs and is used at all controls except preset control. Based on this model, we propose a set of practical controller and a robust design method of feedback controller so that it can attenuate quickly the errors caused by time-delay and modelling error. The proposed model with controller were applied to continuous galvanizing line (CGL) at Kwang Yang Steel Works and we obtained good experimental results on the deviation control of coating weight at top of coil and uniform coating weight on the surface of strip.