Research On The Control Strategy Of Networked System With The Communication Constraints

With the development of computer network communication technology,intelligent sensor technology,the structure of the control system tends to be complicated,so the communication network and the control system are combined to form a networked control system(NCS)which integrates control,communication and management.Compared with the traditional wiring control system,utilizing the network as the transmission medium makes the control system no longer affected by geographical distribution,reduces the cost,improves the intelligence and reliability,is easy to install and maintain,and can be operated remotely.However,all nodes in the system share and use the communication network which also brings some new problems that don't exist in the traditional control system.The main problems are as follows:packet transmission delay due to network channel congestion,packet loss due to packet collision or node access network failure,because the limitation of the network itself,only some nodes can access the transmission medium at any time.These constraints seriously affect the performance of the control system.Therefore,in order to ensure the stability of the control system,it is necessary to take into account the controller design and the network channel scheduling strategy.To sum up,based on the network scheduling strategy,this subject studies and analyzes the control methods of the networked system with limited communication under different scheduling strategies.The main results of this thesis are as follows:(1)Firstly,for networked control systems with limited medium access and network delay,Markov scheduling strategy is utilized as the rule to determine the nodes in the system to access the network channel,the nodes at both ends of the sensor-controller and controller-actuator that obtain the right to use the network channel are described by two independent Markov processes,the time-varying uncertain delay is transformed into uncertain system parameter s according to the processing method of norm bounded uncertain system,the augmented state method is utilized to model the system as a discrete time Markov jump system with uncertain parameters.Based on the Lyapunov stability theory,the sufficient conditions for the asymptotic stability of the system are given,and the feedback gain of the controller is obtained by solving the generalized inverse matrix.Finally,the effectiveness of the proposed method is verified by a simulation example.(2)Secondly,in engineering practice,the control performance of the system can't reach the expected effect because of the uncertain factors such as complex environment and equipment aging,so it is necessary to study the robust control problem in the networked control system.These negative factors are regarded as external interference,and robust H_?controller is designed to make the system have the ability to resist interference.Considers the periodic scheduling strategies,the networked control systems with uncertain network delay and external interference,the system is described as a discrete time periodic system with uncertain parameters,through the Lyapunov stability theory and LMI method to obtain sufficient conditions to make the system asymptotic stable,the robust H_?controller is designed,the proposed controller can make the analyzed networked control system asymptotically stable and with H_?performance index through a simulation example.(3)Thirdly,for the networked control system with induced delay,limited medium access and packet loss,the independent and identically distributed scheduling strategy is utilized to determine the network usage of the system nodes at each time,through two independent Bernoulli random process to describe the packet dropout phenomenon,the closed loop system is modeled as an asynchronous dynamic switching system.Combined with the theory of Lyapunov stability and the processing method of switching system,both the conditions for the system's exponential stability and the design method of state feedback controller to ensure system exponential stability are given.The feasibility and effectiveness of the proposed method are verified by a simulation example.