Coating deviation control in transverse direction for a continuous galvanizing line

A new air knife system for control of coating thickness was developed for a hot dip galvanizing line. The existing air knife system can manipulate only the mean coating weight. The developed new air knife system has the flexible nozzle structure, by which the transverse coating weight can be controlled. The controller is a multiinput-multioutput (MIMO) system which consists of m control inputs (measured value) and n control outputs (nozzle control). Multinozzle control is based on the optimal control algorithm. The controller calculates the m nozzle references according to the n coating weight deviations using optimal algorithm and the models between the coating weight and nozzle gap. The time delay problem was solved by the Smith predictor