Decentralized Control Of The Speed And Tension System Of Cold Strip Rolling Mill Based On Prescribed Performance Method

Cold rolled strip steel is a kind of very important rolled products,due to its smooth surface,high dimensional accuracy,excellent mechanical and technological characteristics,so the cold rolled strip steel has a wide range of applications in aerospace and military industry,petrochemical industry,automobile and shipping,food packaging,and so on.The thickness and shape accuracies are important indicators to measure the strip steel quality,and as the exclusive equipment for producing strip steel products,the reversible cold strip rolling mill maintains constant tensions are the key to ensuring the strip steel product quality and the smooth progress of the rolling process.However,in the actual production process of reversible cold strip rolling mill,the left coiler,the main rolling mill and the right coiler are flexibly connected through the strip steel,and they constitute a complex time-varying system with features of being multivariable,being nonlinear,having strong coupling,and being uncertain,which brings certain challenges to the coordinated and stable operation of the speed and tension system of the reversible cold strip rolling mill.In order to improve the control performance between the speed and tension of cold strip rolling mill and enhance the transient-state and steady-state performance of the system,the following aspects of research work are carried out in this paper:Firstly,according to the actual rolling process of reversible cold strip rolling mill,the mechanism modeling method is used to deduce the left and right coiler tension model,rolling moment model,front and back slip model,slow time variable parameter model of steel coil radius and moment of inertia,voltage equation,torque equation and motion equation of DC motor,and then the dynamic model of the speed and tension system of the cold strip rolling mill is obtained comprehensively.Secondly,aiming at the tracking control problem of the speed and tension system for the cold strip rolling mill under parameter perturbations and load disturbance,a prescribed performance control strategy based on the extended state observer is proposed.The extended state observers are constructed to estimate the system uncertainty dynamically,and the perturbation estimates are introduced into virtual controllers to compensate.Based on the prescribed performance functions,and combined with the fixed-time control theory,the prescribed performance controller is designed for each subsystem.The transient and steady-state performance indicators such as the convergence rate,steady-state error and overshoot of the system are satisfied,and the system states converge within fixed time.Thirdly,aiming at the control parameter setting and output constraint problem of the speed and tension system for the cold strip rolling mill,a fixed time prescribed performance optimization control method based on disturbance observer is proposed.The perturbation observer is used to estimate the uncertainty of the system,and the observation error can converge in fixed time.A time-varying logarithmic barrier Lyapunov function is given to complete the design of the fixed time prescribed performance controller,which makes the output states of the system converge to the predefined range within fixed-time.The main parameters of the controller are optimized by Particle Swarm Optimization-Gray Wolf Optimization algorithm,which further improved the convergence speed and steady-state accuracy of the system.Finally,aiming at the predefined time tracking problem of the speed and tension system for the cold strip rolling mill with unmatched uncertainties,a prescribed performance optimization control method based on predefined time disturbance observer is proposed.The predefined time disturbance observers are designed to dynamically observe the uncertainties of the system,and the observation errors can converge within the predefined time.Based on the new performance function and the predefined time control theory,the prescribed performance controllers are designed.The designed controller can effectively take into account the transient and steady-state performance of the system,and the system states can converge within the predefined time.The artificial rabbit algorithm is used to optimize the controller parameters to further improve the control potential of the control method proposed.