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Research On Multi-model Switching Adaptive Control For Hydraulic Servo System Of Rolling Mill

Posted on:2013-11-08Degree:MasterType:Thesis
Country:ChinaCandidate:P Z ShaoFull Text:PDF
GTID:2231330362462768Subject:Control theory and control engineering
Abstract/Summary:PDF Full Text Request
Hydraulic servo system is the key component of gauge and flatness control system inmodern cold strip rolling mill, and its dynamic and static characteristics has a greatinfluence on the precision of strip. However,the parameters of hydraulic servo system aretime-varying,uncertain and nonlinear,especially some parameters will jump when millpress. For example, elastic stiffness coefficient and the external load force in forceequation of hydraulic servo system will jump to a great value from 0 when the cylinderpiston touches the rigid load, and this will change the model of the system and affects thesystem performance. At the same time, control input of the hydraulic servo system islimited. So the multi-model switching control for hydraulic-servo mill rolling system iscarried out to effectively solve the problem of structure, parameter break and control inputsaturation above-mentioned, which will improve the stability of the hydraulic servosystem, as well as the dynamic static performance in various working conditions, Theaccuracy and quality of rolled strip are also mended. It’s significantly to further extend theapplication of multi-model switching control in practice and put the theory into practice bythis research.Firstly, according to the mechanism equations of major elements, a mathematicalmodel of hydraulic servo system is achieved. Then, to deal with the problem of parametersjump and control input saturation, the corresponding switching multi-model set isestablished.Secondly, adaptive backstepping control of multi- model switching is proposed tohandle the problem of parameters jump in rolling mill hydraulic servo system. The statefeedback controller for each subsystem and the parameter adaptive estimators foruncertain upper bound are designed by backstepping method. To guarantee the system isstable under arbitrary switching, the Lyapunov function disigned by backstepping is usedas a common Lyapunov function. Afterward, a simulation comparison with theconventional adaptive backstepping control is given for verification.Finally, backstepping sliding mode control of multi- model switching is designed in view of control input saturation due to physical limits. To ensure the stability undercontrol input saturation, control saturation is explicitly accounted in controllers of eachsubsystem. And then the stability of the multi-model switching system is proved bycommon Lyapunov function method. Simulation results demonstrate the effectiveness ofthe proposed method.
Keywords/Search Tags:multi-model, switching control, hydraulic servo system, common lyapunovfunction, adaptive backstepping control, control saturation, cold strip rollingmill
PDF Full Text Request
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