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Research On Multi-model Switching Adaptive Control For Electro-hydraulic Servo System Of Rolling Mill With Input Saturation

Posted on:2015-03-28Degree:MasterType:Thesis
Country:ChinaCandidate:Y Z XuFull Text:PDF
GTID:2181330422470698Subject:Control theory and control engineering
Abstract/Summary:PDF Full Text Request
Electro-hydraulic servo system is the key component of thickness control system incold rolling mill, and its dynamic and static characteristics have a great influence on theprecision and quality of strip. However, electro-hydraulic servo system contains nonlinear,parameter uncertainty and external disturbance, especially elastic stiffness coefficient andthe external load force will jump in actual working condition of electro-hydraulic servosystem of rolling mill, which causes the change of system structure and affects the systemperformance. In addition, the input saturation problem that flow of servo valve is limitedalso exists in the electro-hydraulic servo system of rolling mill, which can not be ignored.These problems increase the difficulty of design for control system. In order to improvethe control performance for the electro-hydraulic servo system of rolling mill, multi-modelswitching adaptive control for system with above-mentioned problems is researched inthis paper. The main contents of this paper are as follows:Firstly, the structure and principle of the electro-hydraulic servo position system isintroduced. And then, the convention mathematical models are established in this paper.Furthermore, to deal with the phenomenon of parameters jump, the switching multi-modelsets are achieved.Secondly, focusing on the input saturation in electro-hydraulic servo system of rollingmill, a robust adaptive control strategy based on backstepping is proposed. This strategyintroduces hyperbolic tangent function to deal with saturation, which achieves goodcontrol effect. However, there exists “terms explode” in backstepping method, andbecause of considering the saturation characteristic, the design of the controller is complex.As an improvement, an adaptive dynamic surface strategy is proposed, which simplifiesthe design process of controller. The effectiveness of the strategy is validated bysimulations.Then, focusing on the parameters jump and input saturation in electro-hydraulicservo system of rolling mill, a multi-model switching anti-saturation control strategybased on the common time-varying sliding mode is proposed. Time-varying sliding mode control is utilized to avoid the reaching phase of conventional sliding mode control, andmake sure that the whole system is robust all the time. Multi-model switching controlmethod is used to solve the problem of parameter jump. Lyapunov stability theory is usedto prove that the closed-loop system is stable.Finally, to deal with the immeasurable state, parameters jump and input saturationproblem in electro-hydraulic servo system of rolling mill, an anti-saturation multi-modelswitching control strategy based on observer is presented. In this strategy, observer isdesigned to observe the immeasurable state, and fuzzy logic is used to deal with systemuncertainties. Then, anti-saturation controllers are obtained from dynamic surface method.The measurable load pressure that changes with working condition is considered as therule of switching control, which can ensure the exact switching among sub-controller andimplement effective control for system.
Keywords/Search Tags:cold strip rolling mill, electro-hydraulic servo system, input saturation, multi-model switching control, adaptive control, dynamic surface control, time-varying sliding mode control
PDF Full Text Request
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