Real-time Analysis And Simulation Of Networked Control Systems

Since the beginning of the 21 st century,with the rapid development and integration of computer network,communication technology and control system,the network has gradually been used in control systems forming a new architecture.The advantage of this system is that the network channel is used to share information resources,which makes the system wiring relatively simple,so that it is easy to maintain and expand,and also improves the overall performance of the system.Networked control systems not only have great potential in complex industrial control fields,but also are widely used in medical,military,environmental monitoring,aerospace and other fields.However,the performance of networked control system is affected by its own control strategy.The interference of uncertain network factors will greatly affect the performance of the system.It can be seen that the theoretical study of networked control system is very important to improve the performance of system control in practical applications.The emergence of networked control system has revolutionized the traditional control field,and inevitably brought some defects and problems that cannot be ignored.The study of time delay problems is a key core in real-time research.This is because real-time problems in networked control systems are all caused by delay problems in some ways.For example,due to the wide physical space of the network nodes,the waiting time for packing is too long,and the distributed data is transmitted by multiple packets;the packet loss problem can be regarded as experiencing an infinite delay in the transmission process;the time series disorder of the data packet is also caused by the data packet experiencing different delays,so the delay problem is the focus of current network control system researchers.This thesis introduces the basic problems existing in NCS,and gives a brief overview of the network control system network simulation technology,focusing on the OPNET simulation tool and the simulation principles.This thesis analyzes the real-time strategies of common networked control systems—fieldbus and industrial Ethernet,and introduces the results of current NCS research based on control theory.At the same time,the composition and modeling of network delay are analyzed in detail.In order to study the real-time problem,for the wired networked control system-CAN,the OPNET simulation tool is used to realize the CAN network software simulation and performance analysis based on the non-destructive arbitration mechanism through the three-layer modeling mechanism;For wireless network control system,this thesis improves the wireless network based on IEEE 802.11 protocol,and proposes a real-time scheduling strategy of industrial wireless network based on priority backoff to meet the real-time requirements of the industrial site.And the feasibility of the method is verified by using OPNET simulation.