Research On Control Strategy For The Speed And Tension Multivariable Coupling System Of Reversible Cold Strip Rolling Mill

The speed and tension system of reversible cold strip rolling mill is the basis of safe,efficient work for rolling mill system, and maintaining constant tension is the effectivemeasure to guarantee the strip quality, if the fluctuation of strip tension is very large, thenit not only affect the precision of gauge and shape, even cause strip break. In the actualrolling process, the left coiler tension, the main rolling mill speed and the right coilertension constitute a complex time-varying system of multivariable, nonlinear, stronglycoupled and uncertain. Conventional control strategies mostly use single variable controlprinciple, i.e., the coupling between the speed and tension is ignored artificially, and speedcontrol system and tension control system are designed individually, the control principle,however, restricts the further improvement of control precision and strip product quality.To weaken the coupling among, improve the coordination control performance andtracking control precision, enhance the robust stability, and reduce the control cost of thespeed and tension system, the main contents of this paper are as follows:Firistly, a relatively complete mathematical model for the speed and tension system isbuilt by using the mechanism modeling method; aming at the main rolling mill speedsubsystem with parameter perturbations and load disturbance, an adaptive backsteppingcomtrol strategy is proposed based on integral sliding mode, which improves trackingcontrol precision and anti-interference ability of the system effectively.Secondly, aming at the decoupling and coordination control problem for the speedand tension system, static decoupling and dynamic decoupling are studied respectively. 1)A compound control strategy is proposed based on invariance principle, in whichinvariance principle is used to realize static decoupling; then compound control, which isconstituted by ESO, backstepping and global sliding mode, improves the asymptotictracking performance and robust stability of the system effectively. 2) To realize theinput\output dynamic decoupling and global linearization for the speed and tension system,a differential geometry dynamic sliding mode decoupling control strategy is proposedbased on power exponential reaching law, which weakens the chattering and improve thedynamic and static performance of the system effectively. 3) Considering the influences ofparameter perturbations and load disturbance on the system performance, a nonsingularfast terminal sliding mode control strategy is proposed based on inverse system theory andWNN; in which system model is decoupled into pseudo linear system via inverse systemtheory, and nonsingular fast terminal sliding mode controller for each pseudo linearsubsystem is designed based on backstepping and two-power reaching law; WNN is usedto approximate the uncertain items in pseudo linear system, which improves the trackingcontrol precision of the speed and tension system effectively.Thirdly, the coupling terms in the speed and tension system are taken as externaldisturbances, and then observer design and robust control are studied respectively. 1) Aglobal integral sliding mode adaptive backstepping control strategy is proposed based onESO, which use the decentralized control principle, and the coupling terms and uncertainterm are regarded as total external disturbance, for which ESO is built to conduct dynamicobservation, and the observed value is introduced into the global integral sliding modeadaptive controller for compensation, then realizes dynamic decoupling and coordinatecontrol for the speed and tension system. 2) Considering the influences of parameterperturbations on the system performance, a dissipative Hamilton control strategy isproposed, in which I&I is used to estimate the perturbation parameters, and dissipativeHamilton controllers for the speed and tension outside loops are designed by utilizing theinterconnection and damping assignment, and energy shaping method; the outputs of thespeed and tension outside loops are taken as the inputs of the current inside loops, thencomplete the design of integral sliding mode controllers for the current inside loops.Finally, aming at the tensiometer-free control problem for the speed and tensionsystem, adaptive state observers and Hamilton controllers for the system speed and tensionoutside loops are designed by using feedback dissipative Hamilton theory and “extendedsystem+feedback” method, which realize tensiometer-free control and reduce the controlcost; further, robust controllers for the system current inside loops are designed, whichrealize coordinated control for the speed and tension of reversible cold strip rolling milland2 L interference suppression for the uncertainties.