Research On Control Problem Of Networked Control Systems With Uncertain Time Delay And Packet Dropout

In NCS, the sensors, controllers, actuators and other important components are connected by the communication network, signal and data are transmitted through the network, that has changed the point to point connection method of traditional control system, thus avoiding the laying line between the parts and having solved the problem of high cost and difficulty to have an overhaul in traditional control systems. At present, the network control system has been applied into many fields, such as space system, transportation system, electric power system and so on.However, the network control system is connected to the network, and inevitably brought new problems: such as network delay, packet dropout, etc. In this paper, we study the control problem of linear discrete network control systems with external disturbances and parameter uncertainties.The main research contents are as follows(1)For a class of linear time invariant networked control systems with external disturbances,a H? controller is designed in order to make the closed-loop system mean square stable and meet the prescribed H? disturbance attenuation level. It is known that the system has data packet loss and time-varying delay from the sensor to the controller, and time varying delay from the controller to actuator. The total time delay is less than one sampling period. The uncertainty of delay is turned into the unknown parameters of the system equation so that the system is modeled as a norm bounded uncertain system. Data packet dropout is assumed to be satisfied with the Bernoulli distribution sequence with known probability. Sufficient conditions for the existence of the state feedback controller are given by linear matrix inequality and Lyapunov principle. And the controller design problem is transformed into sloving the feasible solution of the linear matrix inequality. A simulation example is given to prove the effectiveness and feasibility of the design method.(2) Considering a class of linear time invariant discrete network control systems with network-induced delay, packet dropout, external disturbance and system parameter uncertainties,a H? state feedback controller is designed to make sure that NCS is stable. There is a potential for packet loss in both the sensor to controller channel and controller to actuator channel. Network with packet dropout is regarded as a switch switching in a certain rate, and the NCS is modeled as an asynchronous dynamic system with four rate constrains on events. Based on the Lyapunov stability theory and linear matrix inequality method, the sufficient conditions for the existence of the controller are given. Finally, the simulation example is given by using the LMI toolbox in Matlab, and the simulation results verify the feasibility of the method.(3) For a class of linear discrete-time networked control systems with time-varying parameters, an observer based H? state feedback controller is designed. The delay between the sensor and actuator is studied, and the time delay between the controller and actuator is also taken into consideration. It is assumed that the data may be have a loss when transmitted from the controller to the actuator and the packet dropout meet the Bernoulli random sequence. Using LMI and Lyapunov stability theory, sufficient conditions for the existence of controller observer based state feedback is given, finally the simulation results verify the feasibility of the design method.