| The galvanizing on the surface of the steel sheet is an important method for steel anticorrosion. The anticorrosion time is decided by the coating weight on surface of galvanized steel sheet. It is very important to control coating weight precisely according to customer’s demands for improving product quality and reducing cost. Nowadays, the advanced continuous galvanized steel sheet import from foreign. The research on coating weight control is useful to improve proprietary intellectual property and develop proprietary coating weight control system.In this paper, the coating control system in continuous galvanized steel sheet is analyzed deeply, which include coating model preset, longitudinal coating mean control and transverse coating deviation control. In CLECIM coating model, the coating weight is the function of air pressure, distance from air knives to strip and air knives lip gap. The model preset is used for calculating reference values of control variables. In the longitudinal mean control, air pressure and distance are controlled to achieve precise and mean coating weight. And the transverse deviation controls air knives lip gap to improve the coating uniform.The coating weight of the steel is controlled by the coating control system through the traditional PID control. However, there are so strong disturbance in the industry fields that some model parameters are changed, such as air pressure, line speed. In this way, the effort of the coating control system is affected.In this situation, the fuzzy PID controller is introduced into the longitudinal coating mean control system, which adopts the Edward coating weight model. The model is identified using the least square approximation based on the real measured data. The simulation results indicate the fuzzy controller acquires shorter overshoot, shorter adjusting time and greater robustness. Thus, the effort of control system and quality of coating weight on the steel are improved. |
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