Research On Application Of New Type Control Strategy In Mill Hydraulic System

This thesis discusses the application of some new control arithmetic in mill hydraulic servo-system.In the steelworks, rolling mill, the hydraulic servo-system of which especially, need high precision and quick response. The characteristic of hydraulic servo-system directly affects the precision and quality of the product. Some advanced application, such as the product line of iron strip used for cars, requires more excellent response characteristic of hydraulic servo-system. Therefore, In order to reach the goal the influence of some nonlinear factors of the system, such as flux-pressure nonlinear relationship of the valve, time-varying parameters, output noise and the load disturbance, are all should be taken into account. Besides these, the non-consistent behavior of system response in different direction should also be paid much attention to.The thesis first give the nonlinear model of rolling mill hydraulic servo-system, proves that the system is equivalent to a linear time-varying system. The classical adaptive control is suitable to solve such problem. Therefore, Adaptive Pole PlacementControl (APPC) is discussed at first. The stability, convergence and robustness of the close loop system are analyzed in detail. The key factor should be emphasized in application is pointed out. In different rolling schedule the parameters of hydraulic screw-down servo-system always change greatly and rapidly, which result in big transient error and long regulating time if only one adaptive model is considered. Therefore Multi-Model Adaptive Control (MMAC) is adopted to solve this problem. Finally, as a simpler solvent before more sophisticated adaptive control arithmetic put into use, the paper introduces Fuzzy Gain Compensation to solve the problem of non-consistent behavior in different direction. In addition of those arithmetic described above, as an example of the popular nonlinear design technology, the paper simply discusses the feasibility of application of backstepping technology in the controller designing of mill hydraulic servo-system. The paper gives the simulation result of the control arithmetic, some of which are embedded into the real-time control program, gives the result of APPC both under circuit simulation and on one mill hydraulic servo-system.