Analysis Of Time Delay And Control For Networked Control Systems

With the development of the network communication technology and automation control technology, control system based on the network starts widely to apply in the field of industrial control.communication between the various control units of industrial control system from point to point transmission mode into a network-based transmission mode.The networked control system (NCS) not only simplifies the connection of sensors, controllers and actuators and improves the reliability of the system, but also reduces the complexity of the control system structure. However, it gives the control system to introduce the different form time delay that may have the negative influence to control system's stability. The analysis of network time delay to the systems control performance's influence or reducing the network time delay, becomes new problems which the networked control system faces. This paper has studied emphatically the network delay in networked control systems to control system's influence and countermeasure.First of all, the basic concept of network control system is introduced in this paper. The basic problems and characteristic of time delay of the networked control systems is analyzed.The composing and the reason which arouses network-induced time delay in the networked control systems are expatiate.Modeling of networked control systems is given for two type time delay in NCS—short time delay and long time delay. Especially,we relegate the stochastic time delay and time-varying time delay to uncertain portions of the systems,and model the NCS as discrete-time uncertain systems.PID controller in show many advantages in the industry control, but the biggest shortage is no self-adaptive ability. In this paper the fuzzy controller has been designed which can adjust PID control parameters according to system error. It can improve control system ability to adapt parameter change and realize the effective compensation to delay.Finally, a networked control system simulation platform is set up by TrueTime software to verify the designed controller. The simulation results show that controller has carried on a effective compensation to time delay under the simulated network environment and achieves the design goal.At the same time, the influence of data loss probability and network rate on the networked control system is also described.It shows the importance of considering fully each influencing factor to design the networked control system.