Study Of Networked Control System And Platform

Feedback control systems wherein the control loops are closed through a real-time network are called networked control systems (NCS). NCS which integrates computer, network, communication and automatic control, provides several advantages. As a consequence, NCS has became more and more common used, such as manufacturing plants, HVAC systems and many other fields. But NCS also has many problems , including time delay, packet losses and the like. The thesis is devoted to schedule problem, packet losses and the pilot platform E-NCS. The main research works are as follows:First, NCS' background, basic concept, merits and shortcomings are introduced. A survey of NCS research work from control theory and network devices is given.Second, A new strategy of schedule based on sample period is suggested when NCS becomes not schedulable for its dynamic. The strategy improves the performance especially the low priority loops in the control systems. Next, one simplified PID controller is used to compensate the performance degradation when sample period increases in the strategy. Here, TrueTime which is Matlab/Simulink program shows its feasibility.Follow this, on the packet losses problem, the thesis proposed a model considering the time delay. In the process, we take packet losses problem in control system as variant sample period process. Then feedback control law and state estimation are given. The designs are assemble to the time invariant system for the uniform model, although there are some differences. Meanwhile, time synchronization is implemented with ICMP protocol. The uniform model is suitable to many problems in the NCS, such as sample jitter, clock drift and sample period increasing when schedule strategy is applied.Except the theory study, An Ethernet based pilot platform E-NCS is developed. The software and hardware structures are introduced. The E-NCS consists of control module, bandwidth management module, network analysis module and so on. The concepts and critical implements of all modules are given. Some results have been got.The thesis concludes with a summary and perspectives of future research of networked control system.