Rejection of unknown periodic load disturbances in continuous steel casting process using learning repetitive control approach

The design and implementation of a discrete time repetitive controller for the continuous steel casting process that is used for rejection of load disturbances with unknown period are described. If the period of the disturbance is known, the internal model principle may be used to design a controller that will effectively cancel the periodic disturbance. When the period of the disturbance is not precisely known, a discrete time recursive scheme is used for identification of the period. Experimental results that compare disturbance rejection properties of the repetitive controller with those of proportional integral control are presented. Results that indicate the ease and effectiveness of manual tuning for the rejection of periodic disturbances are then presented. When the period of the disturbance is not precisely known, experimental results that demonstrate online adaptation of the repetitive controller are presented