Study On Time-delay Analysis And PID Controller Design Of Networked Control System

Networked Control System (NCS) which transmits data from controller to actuator and sensor to controller by network has been widely used in industry since it implements resource sharing and co-operation for equipments and users in different areas. It increases the modularity and reliability of system while decreasing costs of installation and maintanance. Meanwhile, the introduction of network to control system makes it quite important to analize NCS because it results in several questions, such as network induced time-delay, data loss, scheduling of resources and so on.Without considering other factors of network, the impact of time-delay on NCS performance is analized which indicates that both dynamic performance and stability of system decreases with increasing time-delay, so that time-delay can't be ignored while designing a NCS. Then, the method to determine the stability region of PID controllers in NCS with PID control has been studied. Based on this method, the stability region of Kp is firstly found, then the stability region in K(?)-Kλplane can be determined under a fixed Kp, all stability region of (Kp, Ki, Kd) will be obtained by sweeping over Kp.The obtained stability region provides parameter regulating range for intelligent controller design of NCS.The performance of NCS using PID control decreases for PID controller doesn't have self-adaptive ability to adjust control parameters with variable time-delay and system parameters. A Fuzzy-PID controller has been designed which can adjust PID parameters according to system error so that the impact of time-delay on NCS gets mostly compensated, improving system ability to adapt parameter variation and resist disturbance.Finally, a NCS simulation platform is established by TrueTime toolbox which provides a simulated network environment to verify the validity of signed controllor. The simulation results evidence that Fuzzy-PID controller makes a good compensation to the impact of time-delay on NCS and output can quickly track input signal of system. In addition, the impact of data loss probability and network rate on NCS is also analized to demonstrate the importance of design NCS combining network and control.