Model-based Research On Networked Control Systems

Introducing network into NCS (networked control systems) result in distributed time delay. The paper analyzes distribution of time delay in NCS and the factors that have effects on the time delay. Three kinds of strategies, namely ensuring QoP, ensuring QoS and giving attention to both simultaneously, were summarized out. In the three, the first and second can't acquire control purpose, for they either only consider the control performance demand, or unilaterally emphasize the network service quality. Because of simultaneously considering the network implementation at the time the control system was designed, the third benefit setting up the whole performance, for this, the third has become main strategy.The input-output model-based NCS addressed in this paper is the third strategy. A key idea about this class of system is to introduce a plant's input-output model and a buffer to overcome the defect of feedback lag introduced by the network usage. When the feedback is unavailable, the control output is computed based on the plant model output, and when available, based on the plant output, meanwhile, the plant model is updated with the plant output.Some simulations are used to verify our algorithm, and the results show that the algorithm is valid and convenient. At last, under two transfer modes, the necessary and sufficient condition for closed-loop stability of a class of SISO systems with model error is derived.