Research On Control Problems Of Networked Control Systems

Networked control systems have attracted much attention because they adapt to the distributed, networked and intelligentized development direction of control systems. This thesis is concerned with state estimation, LQG optimal control, generalized predictive control and delay-dependent stabilization of networked control systems, which takes network-induced time delay and packet loss in both the feedback channel and control channel into account. The main contents are given as follow:Firstly, a prediction-based networked state estimation algorithm is proposed to compensate for the influence of network-induced time delay and packet loss. The performance of the algorithm is theoretically analyzed, and it is pointed that although it achieves a good effectiveness on compensation, its estimation error appreciably increases with the increment of network-induced time delay and packet loss. The stability condition of this algorithm is also discussed. And simulation and experiment results are given to illustrate the effectiveness of algorithm and correctness of theoretical analysis.Secondly, using the prediction-based networked state estimate- ion algorithm, a networked LQG optimal control algorithm is proposed to compensate for the influence of network-induced time delay and packet loss on control performance. The design method of networked LQ optimal controller, which can compensate for the network-induced time delay and packet loss, is given using dynamical programming. With the analysis of the influence of control signal transported through network, the prediction-based networked state estimation is further developed under the condition that network-induced time delay and packet loss simultaneously exist in both the feedback channel and control channel. The separation theorem is proved to hold. Simulation and experimental results are given to demonstrate the effectiveness of algorithm and correctness of theoretical analysis.Thirdly, a polynomial-model-based networked generalized predictive control algorithm is proposed which compensates for the influence of network-induced time delay and packet loss using minimal predictive step and control increment vector, respectively. The relations between network-induced time delay and minimal predictive step, and between packet loss and control increment vector are discussed. With the iterative optimization approach, the design method of polynomial-model-based networked generalized predictive controllers is given. Furthermore, a networked generalized predictive self-tuning controller is discussed, based on the networked iterative least square identification algorithm which reduces the influence of network-induced time delay and packet loss with output prediction. Simulation and experiment results are given to show the effectiveness of algorithm and correctness of theoretical analysis.Fourthly, a state-space-model-based networked generalized predictive control algorithm is proposed in the similar way to the polynomial-model-based case. The design method of the controller is also given. Simulation and experiment results are given to show the effectiveness of algorithm and correctness of theoretical analysis.Fifthly, an improved method of networked delay-dependent stabilization, which can counteract the influence of network-induced time delay and packet loss, is proposed. With a linear nominal system as a controlled plant, the improved method overcomes the conservativeness of the derived condition by considering an integral item which was ignored in the past research of networked control systems. For an uncertain linear system, the design method of networked guaranteed cost controller is discussed with delay-dependent approach. Numerical and experiment results are given to illustrate the effectiveness of the algorithm and correctness of theoretical analysis.