PROFILE AND FLATNESS CONTROL SYSTEM IN 1700mm HOT STRIP MILLS OF ANSTEEL

Varying contact-length backup roll and linearly variable crown work roll are provided for improving the mill performance of profile and flatness control. Integrated with theses technologies, relevant profile and flatness control models are developed for hot strip mills on the basis of large amount of finite element calculation. These models include shape setup control model in process control system, bending force feedforward control model, crown feedback control model and flatness feedback control model in basis automation system. Such a profile and flatness control system with full functions is applied in 1 700 mm industrial hot strip mills of Ansteel. Large amount of production data shows that the crown precision with the tolerance of±18 μm is over 90%, the strip percentage which the actual flatness is within ±25 I-unit surpasses 96%, and general roll consume is reduced by 28% by using the profile and fiatness control system. In addition, schedule-free rolling is realized.

Adaptive Coordinated Control for Hot Strip Finishing Mills

To further improve the control accuracy for strip dimension of hot strip mills,an adaptive control scheme is investigated for a hot strip finishing mill based on the decentralization and coordination among the controllers of gauge,tension and looper.Consequently,the adaptive controller designed can regulate simultaneously the strip exit thickness,the strip tension and the looper angle to ensure better performance of the strip quality of finishing mills.Moreover,the control scheme is proposed in consideration of the essential nonlinearity and the unavoidable friction phenomena in the mechanical system,so the controller can be efficient in a wider range of working situations.The simulation results of a model obtained from a real hot strip finishing mill show the effectiveness of the proposed control scheme in comparison with the conventional control method.

Comprehensive Shape Control Technology for CSP Hot Strip Mills

With the increasing demand on higher strip quality, the profile and flatness of hot rolling strips have become subjects of concern, particularly for compact strip product(CSP) hot strip mills. Based on the roll contour, control model, and rolling process, a comprehensive shape control technology is proposed and applied to CSP hot strip mill of Lianyuan steel, which includes optimization and design of the work roll contour and varying contact back-up roll(VCR) plus backup roll contour, analysis of the flatness feedback control model, as well as improvement of the rolling process control system. The application of the technology has significantly improved the shape control performance. The roll wear is improved and the general roll consumption of the finishing mill is reduced by 29.86%.The percentages that satisfy the control target ranges of the average strip flatness and crown are increased by approximately 15.40%and 14.82%, respectively. The rejection rate of grade Q235 due to shape quality problem is reduced monthly by 39.69%, which creates significant economic benefits for the plant.

Guaranteed cost sliding mode control for discrete-time looper systems in hot strip finishing mills

A guaranteed cost sliding mode control(SMC)algorithm is investigated to further improve the control accuracy of looper-tension systems in hot strip finishing mills.First,a global sliding mode surface function is designed by linear matrix inequalities and guaranteed cost technique,which can force the system states into switching region initially,and can guarantee the system robustness with a good performance during the whole control process.Then,a novel reaching law is designed,which can satisfy the sliding mode reaching conditions.Simulation results demonstrate that the proposed control scheme has good stability and robustness comparing with traditional SMC.The designed controller can regulate the strip tension and looper angle to ensure better performance,which is very suitable for complex looper systems.