Position control method of a non-contacting conveyance system for steel strip

Electromagnetic application system to improve the surface quality of steel strip is getting popular because customers demand better surface quality of steel strip. To realize such a requirement, non-contact conveyance methods by means of air floater and electromagnetic levitation and propulsion were considered. However, air floating method is not easy to control of the position of steel strip since the system is highly nonlinear. And thus, the application of a magnetic levitation and propulsion to steel strip conveyance is suitable. Sensors measuring positions of steel strip also need to be non-contact in order to maintain noncontact and simple characteristics of the system. This paper proposes the method of the spatial position estimation of steel plate without using sensors. This method simplifies non-contact conveyance system and cuts down expenses of the system. Spatial positions of steel strip can be estimated by currents supplied for electromagnet to maintain a fixed air gap. Estimated positions are then fed back into the control system to do position control. Computer simulation and experimental results are provided to verify the suitability of the proposed system performance and concept.