Performance Study of Fuzzy Based Networked Control System

Abstract

Networked control systems (NCS) are distributed computing and control systems with sensors, actuators and controllers that communicate over a shared medium. The distributed nature of NCS and issues related to the shared communication medium pose significant challenges for control design, as the control system no longer follows the rules of classical control theory. The main problems that are not well covered by the traditional control theory are varying time delays and packet losses. The change of communication architecture introduces different forms of time delay uncertainty in the closed loop system dynamics. These time delays come from the time sharing of the communication medium as well as the computation time required for physical signal coding and communication processing. Moreover, the time delays in a control application can degrade a system’s performance and even cause system instability. Due to availability of powerful microprocessors the complex processes which involves higher order equations can be controlled easily. With increased complexity of the process there have been growing demands of controllers which can outperform the conventional controllers. So the new intelligent techniques such as fuzzy logic control, artificial neural network based control and genetic algorithm, etc have been invented. This thesis proposes controller, which provide robustness against the challenges of NCS, namely varying time-delays. The thesis includes a literature review of recent stability and control design results in NCS. To avoid the system instability due to time delays first conventional PID controller is designed for varying time delays in MATLAB. Further Intelligent control technique like Fuzzy control is implemented. Performance of all these controllers compared on the basis of certain performance indices. In order to verify the results of control design, the results of the thesis indicate that the intelligent controllers well suited for NCS.