Research On Delay Compensation Of Network Control System

With the development of computer technology, communication technology and network technology, the traditional control structure for its modularity and integration is limited. Network Control System (NCS) has been widely applied in many aspects in industris. Compared with traditional control system, the biggest difference lies in function equipments (sensors, controller and actuator etc), of which distribution in different geographical space, through the network realization between each node of the data and information exchange, and each node has calculation, analysis and processing and communication ability. NCS has many advantages such as lower cost, high reliability, easy installation, realizes remote operation and control, easy to realize system diagnosis and easy maintenance.Although there are many advantages of network control, however, it's time consuming that take to enable the transmission of information into the communication network system, so the network delay is inevitable. There is an increase of network delay to make the difficulty in analysis and design of network control system, reducing the system control performance and may even undermine the entire system stability. Therefore, it has a positive meaning to reduce the delay of the system's network to compensate to improve the performance of the control system.First, this paper analyzed the causes about time delay in network control system, gave the characteristics and the establishment of the system model by using Lyapunov function. After analysis of the data exist in the communication network and the establishment of the mechanism of loss of the equivalent model, along with exponential stability of asynchronous dynamical systems theorems and drawn to ensure control with data packet dropout conditions for exponential stability.Secondly, the paper established the model of a DC motor controlled object and researched the influence of network delay on system stability and dynamic performance in MATLAB/Simulink simulation environment, and compensated for the delay of network control system by using Smith compensator initially. Additionally, taking into account the Smith compensator is based on precise mathematical model, to overcome the impact of changes to the system, combined with incomplete derivative-forward of the control method to compensate the delay.Then, taking into account the discrete characteristics of the network, used discrete-time simulation toolbox SimEvents to establish the network model, and used Smith compensator combined with fuzzy immune PI control algorithm, according to the change of control of the amount of PI controller parameters to adjust, choose appropriate parameters, effectively improved the control performance. At last charged with a DC motor for the simulation. The simulation results showed that the method can effectively improve the dynamic performance and steady state performance.