The Control of Sheet Motion in a Hot-Dip Galvanizing Line by Electromagnetic Actuator

Control of steel sheet shape and vibration at the air knives can increase the quality, save zinc and reduce costs. In this paper, an electromagnetic actuator set is designed toevaluate the feasibility of using active magnetic levitation technology to control vibration of the steel sheet at the air knives. Electromagnetic actuators and eddy-current position sensors are used. Because there are welding lines on the steel sheet causing the unsmooth thickness of steel sheet, multi sensor technologyis adopted to make the performance calculation resultreflect the steel sheet’s real status. For the proper sensor placement, the modal analysis of the steel strip is applied. In addition, the location of the electromagnetic actuator is designed according to the principle of “equal rigidity�. So the control parameters used in laboratory can be referenced to that of the workplace. Then PID controller is used to control the sheet motion. In order to get enough forcesto control vibration, cross-section within the magnetic loop is increased, and one kind of new material with more saturation flux is selected. Through experimental verification and galvanizing line test, the set can stabilize the sheet motion greatly, improve the galvanizing quality and save zinc.