Development and Control of Networked Servo System

Abstract

Control systems where the control loops are closed through a communication network are called Networked Control System (NCS). Research on NCS has received increased attention in recent years due to the advancement of control,computation and communication technologies. NCS makes the design and implementation of control systems with reduced complexity due to simpler installation and easy maintenance. But the insertion of the communication network in the feedback control loop introduces delay from sensor to controller and controller to actuator, that degrades the control system performance and also causes system instability.This thesis focuses on development of a networked DC Servo control system using LabVIEW and Peripheral Component Interconnect(PCI) card.The controller design for a NCS can be categorized into indirect and direct approach. An indirect approach controller design considers ¯rst without delay followed by design a suitable delay compensation technique. A PID controller with a Smith predictor as a compensater is implemented in real-time networked control of servo system. The above PID controller is tuned using gain margin and phase margin speci¯cations and Zigler-Nichols method are implemented. A direct NCS design approach in the other hand considers the delay as well as packet loss characteristics with system dynamics at one go.This approach gives more information about each instant of the system.It uses Lyapunov approach to design of asymptomatic stabilization of
the system, the above stabilization uses a switched approach for NCS sta- bilization with packet loss and delay is proposed. The switched approach divides the NCS as di®erent subsystems considering both delay and packet loss, then designing of controllers for each subsystem. According to packet loss, the subsystems and controllers are switched to stabilize the NCS. In this approach the feedback gains are calculated by solving Linear Matrix Inequalities (LMIs).
Both direct and indirect controller design approach are simulated using MATLAB and SIMULINK. Some Hardware in Loop simulations are also performed on a Servo System.A realtime networked servo control system has been developed using LabVIEW. Only indirect controller approach is implemented in this environment to remotely control the servo system. The results obtained by using PID controller and Smith predictor have been analyzed and it is conrmed that these controller provide good performances.