Research On Stability And Control Strategy Of Networked Control System With Quantized Feedback

Networked Control Systems(NCSs)is a kind of closed-loop,real time and distributed control system,which transmits and changes the information via network.In comparison with traditional control systems,the NCSs bring many advantages along with many problems,such as network-induced delays,packet dropouts and reordering,bandwidth constraints,coupled with modeling uncertainty and external disturbance,etc.,which make the analysis and synthesis of such composite systems extremely difficult.In addition,since some signals are not easy to be coded,the introduction of quantizer is necessary,which inevitably introduces the influence of quantization error.These problems will lead to the decline of system control performance,so it is of great significance to study the theory of networked control systems with quantization.This thesis mainly analyzes and studies the stability and control strategy of the quantized feedback control system.The system model is established by considering the problems of network-induced delays,quantization,disturbance and bandwidth constraints,and then based on the Lyapunov stability theory and linear matrix inequality(LMI)technique to analyze the system performance,stability and controller design.The specific research contents are as follows:Firstiy,considering the network time delays and the uncertainty of the system to establish appropriate system modeling,logarithm quantizer is applied to the status and input of the system respectively,and convert the quantization error into sector bounded form.Then,the Markov chain with known transition probability is used to describe the random variation law of network delays,and the control system is modeled as networked Markov jump system.By constructing the lyapunov-krasovskii functional,the LMI method is applied to obtain sufficient conditions for the system to be stochastic stability with H_?performance index?,and the design method of the quantitative feedback controller is given.Secondly,then further aiming at the influence of external interference and network delay on the control system,the problem of quantized output feedback control based on observer is studied.The new network system model is constructed for the influence of the system without disturbance and disturbance.The Lyapunov stability principle and the LMI inequality method are applied to give the sufficient conditions for the asymptotic stability of the network system and the design method of the quantitative feedback controller.And through numerical simulation,the influence of disturbance on the convergence rate of the system is obtained.Thirdly,then considering the influence of network bandwidth constraint,the state feedback control problem of hybrid trigger NCSs with network delays and disturbance is studied.Hybrid-trigger transmission scheme and logarithmic quantization are used to improve the transmission efficiency of data in the control system.Due to the influence of hybrid-trigger transmission scheme and quantization,the original control system model is reformulated as a new hybrid-triggered NCSs with communication delay,using Lyapunov-Krasovskii functional method and LMI technique,given the sufficient conditions for the system to be stochastic stability with H_?performance index,and the design of controller and trigger parameters can be obtained.Finally,the effectiveness of the proposed method is verified by simulation results.