Research On Nonlinear Modeling And Vibration Suppression Control Strategy Of Vertical And Torsional Vibration Of Rolling Mill

The rapid development of modern industry and science and technology have higher and higher requirements for rolling speed,surface quality and dimensional accuracy of rolling strip.In the process of rolling mill production,rolling mill vibration caused by the change of rolling process,the different quality of strip and plate,the burst of external disturbance,mechanical aging and other problems have always been the bottleneck problem restricting the development of high speed and high precision rolling.In this thesis the vibration control of rolling mill is systematically studied and the vertical torsional vibration model and control measures are proposed.Firstly,the vertical torsional vibration of the main drive system and vertical drive down system are modeled.In the main drive system,the factors that are easy to induce mill vibration in actual working conditions are analyzed,and the system models including nonlinear friction force,nonlinear damping,time-varying stiffness,current harmonics and external disturbance are constructed.The rolling mill torsional vibration model is established by means of the balance relationship between the motor end and the roll end established by Lagrange equation.In the vertical pressing system,the dynamic model of rolling force which is affected by deformation resistance,tension,strip width,stress state and other variables are constructed.The dynamic control process of the hydraulic cylinder is described.The spool displacement model under the influence of flow rate is established,and the vertical vibration model of rolling mill is constructed by combining the above two models.Secondly,to solve the torsional vibration problem,the torsional vibration can be suppressed by realizing the control target of roller speed stable and accurately tracking the specified speed.Based on the established torsional vibration model,a finite time predetermined performance control method is developed to improve the operating performance of the main drive system.The torsional vibration caused by overflow of input torque is suppressed by adaptive estimation method.The designed instruction filter controller realizes the progressive tracking of roll speed,avoids the repeated differentiation of virtual controller,and reduces the complexity of control.Through Lyapunov theory and simulation,it is proved that the designed controller can effectively suppress the rolling mill torsional vibration.Finally,to solve the vertical vibration problem,the vertical vibration of rolling mill is suppressed by reducing the change of roll displacement when vertical vibration occurs.Based on the established vertical vibration model,the predetermined performance function is improved to ensure the rapidity of roll displacement recovery and minimal overshoot when vertical vibration occurs.In the case that some states are not measurable,the output feedback control strategy is developed.The state observer is used to estimate the vibration velocity and acceleration of the roll,and the voltage control rate is derived backwards.The Lyapunov function constructed proves that the designed output feedback controller can effectively suppress the vertical vibration of the rolling mill.Simulation also verifies the effectiveness of this control strategy.