Study On Repetitive Control System For Cold Strip Roll Eccentricity Compensation

Plate and strip in the national economic development has an important position. The thickness control accuracy is the main standard for judging the quality of plate and strip. Roll eccentricity is the main reason that results thickness fluctuations of the strip. The roll eccentricity has a serious effect on the best thickness control requirement. In order to improve the precision of thickness control, AGC is studied to know how to compensate roll eccentricity in view of the existing in the rolling process of roll eccentricity. The conventional PID control of roll eccentricity compensation exists the phenomenon of serious phase delay and amplitude attenuation, and that phenomenon makes the roll eccentricity compensation cannot reach expected effect, even cause the failure of compensation.In this paper, based on the principle of repetitive control, a compound control system is combined with repetitive control and PI control was designed. A simulation model was established to simulate the composite control system with four rolle r mill in the laboratory.First, based on repetitive control theory, a new repetitive control compensation method, and design conventional repetitive controller was proposed. For input signal of repetitive controller must have strict periodicity, A new algorithm that make the plate thickness feedback signals sequence transform into angle domain signal sequence according to the order ratio analysis principle was proposed. So ensured that the eccentric signal contains in feedback signal have strict periodicity. And the wavelet packet transform to extract the eccentricity signal was used to remove the interference signal.Then set up the model of roller eccentricity, and research the conventional AGC system. After the analysis of the problems existing in the eccentricity compensation, a new compound control system was established, including band-pass filters, the intermittent sampling controller, and the internal mold generator. The band-pass filter was set to isolate thickness feedback signal of roll eccentricity signal added to the repetitive controller. The intermittent sampling was used to overcome the problem of the plate thickness signal delay, and finally the compound control system was established.Finally, the composite control system was put into Simulink environment to simulate, the plate thickness fluctuation curve of the simulation are compared with conventional PID eccentricity compensation board thickness fluctuation curve, and the result of simulation verify that the compound control system can limit the thickness fluctuation curve.