Research On Shape Control Target Model Of Cold Strip Rolling

The shape control target model of cold strip rolling is taken as research object in this dissertation, the in-depth theoretical research and industrial validation are done, and that have very important theoretical value and realistic meaning for independent innovation in shape control core technology of large-sized strip tandem mill.First, the new concept of shape control target contains the flatness target and the cross section shape target is proposed, which is more clear and specific, more convenient to applying, compared to the traditional flatness target curve which is certain form of the transverse distribution curve of residual stress in the rolled strip, and characterizes the flatness condition of rolled strip, and be used in the flatness closed-loop control. In the production, the rolled strip requires not only good flatness, but also good cross section shape (strip crown). Therefore, this paper proposes the new concept of shape control target, which consists of two interrelated contents, one is the flatness target used in the flatness closed-loop control, and the other is the cross section shape target used in the cross section shape and flatness pre-set control.Second, the reduced order model for flatness discrimination is proposed, its calculation speed is fast, and its calculation stability is good. The calculation speed and the calculation stability of the traditional strip element method for flatness discrimination are analysed, the improved model of deflection function is established by inducting the conditions of second derivatives continuity on the nodal lines and the force boundary conditions of free sides. The deflection function and its first and second derivatives can be expressed only by the deflections of the nodal lines, not by the deflections of the nodal lines and their first derivatives. So the unknowns are reduced by half. According to the statics minimum potential energy principle, the calculation model for flatness discrimination is established, the orders of characteristic matrix are reduced from 2(n+1) to (n+1), therefore the computing speed is increasing, the calculation stability is good.Third, considering the requirement of annealing technics, the converse stepwise independent optimization method and its fast calculation method with which the shape control targets are established are proposed, its calculation speed is fast, and its calculation stability is good. The flatness discrimination model and the strip deformation model are separately calculated, and the flatness targets and the cross section shape targets of every stand are attained with stepwise optimization, the simultaneous iterative calculation in the traditional positive simultaneous optimization method is avoided, so the speed and stability of the calculation are improved. The calculation speed is improved compared to the traditional method, but the calculation time is about 888 s, it is difficult to meet the real-time performance of the engineering on-line application. Through analysis of this method calculation process, it is found that optimization of the stylebook of the flatness target spend most of the calculation time. Therefore, the fast calculation formula of the stylebook of the flatness target is linear regressed from a large number of the off-line calculation results, and the stylebook of the flatness target is calculated with this fast calculation formula, the converse stepwise independent optimization fast calculation method with which the shape control targets are established is formed, the calculation time is reduced to 0.703 s, which can satisfy the real-time performance of the engineering on-line application.Fourth, the shape set control method based on the cross section shape target is proposed, and achieves the diplex control of the cross section shape and the flatness target, its calculation speed is fast, and its calculation stability is good, which is suitable for the engineering on-line application. The set control calculation is done with only one rolls deformation model, the simultaneous iterative calculation in the traditional shape set control method is avoided, and make the set control calculation more simple, so the speed and stability of calculation are improved, the calculation time is about 1.781 s, industrial validation has perfect effect.Finally, the calculation method of the on-line flatness target is proposed, the speed and precision of calculation can satisfy the real-time performance of the engineering on-line application, which can be used in the flatness closed-loop control. The flatness target on-line compensation model is established, and the perfect on-line flatness target model is formed with the integration of the flatness target on-line compensation model and the converse stepwise independent optimization fast calculation method with which the shape control targets are established, the calculation time is about 0.765 s, industrial validation has perfect effect.In brief, the shape control target model of cold strip rolling and the shape set control method according to the cross section shape target and the calculation method of the on-line flatness target proposed by this dissertation are suitable for the engineering on-line application, and the precision, speed and stability can all satisfy the real-time performance of the engineering on-line application, and the applied value is well.