Controller Design And Stability Analysis For Networked Control Systems With Time Delay

The networked control system is paid more attention to by scholars with the rapid development of computer technology and network communication technology. It has many advantages such as sharing information resources, reducing wire and extending and maintaining easily. On the other hand, the two main problems, the network induced time delay and data packet dropout, are brought into the control system. Therefore, it is impossible that traditional control theories are applied to networked control systems. The problems of modeling and controlling for the nonlinear networked control system, the model-based networked control system and the variable-sampling networked control system are studied in the paper.In the paper, the problems of modeling, controller designing and stability analyzing for the nonlinear networked control system are settled by combining the fuzzy control theory with the linear networked stochastic control theory. A nonlinear system is exactly described as several local linear fuzzy models by using T-S fuzzy theory. When designing controller for the linear subsystem, firstly, the state transition matrix is derived on condition that distributing probability of the network-induced delay is known; Afterwards, the stochastic optimal controller for the linear subsystem is designed and stability is analyzed adopting dynamic programming and linear stochastic optimal theory. The simulation results show that the control scheme for the nonlinear networked control system presented in the paper is feasible and effective.The affine nonlinear network control system is further studied using the Delta domain discrete theory. Firstly, the nonlinear plant is described as several local linear fuzzy models by using the method of Taylor series expansion. Afterwards, Delta operator is introduced into the networked control system, the stochastic optimal controller and the tractor for the linear subsystem are designed in Delta domain, and stability is analyzed by using dynamic programming and linear stochastic optimal theory. The simulation results show that infinite-time stochastic optimal controller in Delta domain designed in the paper is effective.In order to lessen the influence of network on control systems, the structure for the NCSs is network connecting only between the sensor and the controller. The certain controller for the model-based networked control systems is designed and stability is analyzed. Two innovations for the structure of model-based networked control systems are done in the paper. Firstly, the observer is laid on the side of controller node, and digital observer instead of traditional observer can save the cost effectively. Secondly, the signal processing unit is added before the signal from the sensor reaches the controller, thus the tolerance value of the maximal sample period of the system is greatly increased. The model-based networked control system design is designed as follows. Firstly, the gain matrix of continuous controller is obtained according to continuous model of the plant and the expected pole values without considering the influence of the network. Then, by using the controller to control the system, considering the influence of network, the tolerated maximal sampling period is obtained. The necessary and sufficient conditions for ensuring the system's stability and sufficient conditions for ensuring Lyapunov stability are both put forward for the model-based networked control system based on new structure with time delay and without time delay, and the change zone of the sampling period for ensuring the system's stability is given.By adopting event-time drive method, the controller design and stability analysis for the networked control system based on variable-sampling theory is explored in the paper. Above of all, the selecting principle for the continuous system's tolerance maximum sampling period is studyed. According to variable-sampling discrete model, the necessary and sufficient condition for ensuring the system's stability is putted forward, and the steps for control gain is given. Then, the variable-sampling discrete model with observer is studied, and design method for the controller and the observer are given. Finally, the controller for the time delay networked control system is designed based on variable-sampling theory, and the experiment is conducted on the networked platform based on the Lon technology. The results of the experiment prove that the designed controller can ensure the networked control system's stability.