Control And Application For A Class Of Networked Nonlinear Systems

With the high-speed development of information technology, the signals more andmore need to be transmitted between long-distance parts. At the same time, it has higherrequirement of real-time and accuracy. But long-distance transmission inevitablely leadsto time-delay, which has a bad effect on the system performance, even leads to the wholesystem unstable. So how to deal with the time delay attracts more and more attention ofscholars both at home and abroad. The networked delay based on linear system andnonlinear system both has been studied at present. While, because of the unavoidabledisturbance and inaccurate model, the practical systems are mostly nonlinear ones.Therefore, we discussed the nonlinear systems in the paper, aimming at dealing withnetworked delay problem. And then apply the proposed control strategy into the actualrolling mill system.Firstly, give the mathematical model of hydraulic automatic gauge control system incold rolling mill. Due to the fact that the thickness gauge always installed in the distanceto the roller which produce the thickness of the sheet, it inevitably produces networkeddelay problem. According to the practical running mechanism of cold rolling mill, we givethe dynamic equations of the system. Then, based on the equations, two classes ofnonlinear mathematical model for control are presented in view of the different researchemphases.Secondly, in view of the class of networked nonlinear systems with constant inputand feedback delays, design dynamic neural network observer to estimate theunmeasurable state firstly. And then, based on the observer, Smith predictor method isused to design controller to deal with the delay problem.Thirdly, based on the mathematic model of cold rolling mill system which wepresented before, considering the situation that not all states can be measured, design theextended state observer to get the unknown states and nonlinear functions. Then, designthe controller based on Smith predictor to solve the constant measurement delay problem.Finally, in view of the time-varying measurement delay problem in the hydraulic automatic gauge control system, design applicable controller to overcome the delayproblem. And Lyapunov stability theory is used to prove the exponentially stable of thesystem. Besides, simulations for a1700single rolling mill are presented to verify theeffectiveness of the proposed controller.