Study on Stability of Steel Strip under the Electromagnetic Shape Controller

In a steel process line, shape controllers of steel strip using electromagnets are important devices for improving strip quality and line speed. It is confirmed that the devices are beneficial when these are applied to Continuous Galvanizing Line (CGL). However, it is necessary to avoid a static instability phenomenon by negative spring of the electromagnet, and a spill-over phenomenon by the high gain of the control system in this device. We proposed an analysis model combining the control system with the steel strip. The model was applied to a real machine to confirm the availabilities. Moreover, this paper discusses the static instability phenomenon and the spill-over phenomenon.