Dynamic Model Building Of Rolling Mill System For Thickness And Shape Control Of Strip

The shape and thickness qualities of the strip are very important indexes, and the rolling mill system is a complex multivariable nonlinear system, the dynamic characteristics of the rolling mill are complex which have strong influence on the shape and thickness qualities. At present, the studies on the strip thickness system mainly concentrated on the individual items and partial items, and the study on the integral mill system based on thickness control is rare; the studies on the strip shape system mainly concentrated on the static shape preset theory, and the study on the mill dynamic model and simulation based on shape control is rare. So that, based on thickness and shape control, the dynamic model building theory and simulation of mill system was deeply studied.Take the complex relationship of parameters in the rolling process into consideration, the integral dynamic model of 4-h mill based on thickness control was built. The dynamic model includes the rolling process model, the dynamic model of mill stand-rolls and the dynamic model of hydraulic servo system. The three models coupled together and are a organic whole. According to the relationship among the three models, the coupled model was established and linearized. Then, the MIMO transfer function of 4-h mill system was established. This model is different from the individual items and partial items of mill system, but it was built from the global perspective.Based on the linearized dynamic model based on thickness control, the robust controller was designed for the electro-hydraulic system based on the simplified H_∞mixed sensitivity method. The H_∞robust controller is designed for the thickness control system based on the mixed sensitivity robust control theory. Simulation results and comparison with the effect of PID controller show that the robust controller designed has better disturbance attenuation performance for parameter uncertainty and external disturbance, and the effective of the controller was approved.In order to build the dynamic model of mill system based on shape control, the dynamic models which include the rolling direction, the vertical direction and the axial direction of rolls must be built firstly. In this paper, the rolls were taken as elastic continuous bodies, which was different from the theory taking the rolls as lumped masses. The free and forced transverse vibration models of rolls were built based on continuous body dynamic theory. The natural frequency, principal mode and motion equations were determined; the dynamic characteristics of rolls were studied when the rolls were acted by different forces, and the simulation was made. This model is the basic model of the dynamic model based on shape control.The integral dynamic performance of tandem rolling mill is not influenced by the dynamic of rolling mill, but influenced by the moving strip. The two dimensional model and three dimensional model of moving strip in the rolling process was established based on moving beam theory and moving sheet theory respectively. Then, substitution of the tension equation and stress distribution equation into the two dimensional dynamic model and three dimensional dynamic model, based on Galerkin truncation method, the partial differential equation was discrete. The natural frequencies of moving strip are determined. The stability of moving strip was studied and the simulation in time domain was made.The dynamic model of rolling mill system based on the shape and thickness control was established. First, the coupled model of rolling process and transverse vibration model of rolls was built (here simply called coupled dynamic model). Then, the srip-rolls coupled static model was built and used to compensate the dynamic model. Last, considering the characteristics of static model and dynamic model, coupled the dynamic model and static model, based on numerical method, the dynamic model of rolling mill based on shape and thickness control was established and the simulation was made.The theory system of dynamic model building of rolling mill based on shape and thickness control was established in this paper. The static model building theory was broken, and the rolling theory was developed. It is significant for developing the dynamic model building of rolling equipment, developing new rolling technology and equipment.