Stability and implementation of model based predictive networked control system

Official URL: http://192.168.1.20/record=b1293644 (Table of Contents)

Digital control systems that have computer nodes which communicate over a data loss and random delay prone common network are called Networked Control System (NCS). In a typical NCS, the sensor, controller and the actuator nodes reside in different computers and communicate with each other over a network. Random delays and data loss of the communication network can endanger the stability of the NCS and retransmission of data is not feasible in control applications since it adds delay to the system. The aim of this thesis is to verify that the distributed NCS method called Model Based Predictive Networked Control System (MBPNCS) can be implemented using an observer and that it can control an open loop unstable plant. MBPNCS compensates for missed and late data by implementing an intelligent predictive control scheme based on a model of the plant. MBPNCS does not use retransmission and does not guarantee timely delivery of data packets to each computer node since this solution is not feasible on every control application and every communication medium. Instead, MBPNCS offers a control solution that can work under random network delay and data loss by the use of a predictive architecture that predicts plant state estimates and respective control signals from actual plant states. In this thesis, MBPNCS is described along with an introduction to a theoretical stability criterion. This is followed by an implementation of MBPNCS with two different plants. First, MBPNCS is implemented with an observer based DC motor plant to demonstrate the system’s efficiency with an observer. Next, MBPNCS is implemented with an inverted pendulum to demonstrate the system’s efficiency with an open loop unstable plant. Finally, two separate MBPNCS’s are implemented over a common network to demonstrate the systems efficiency and feasibility in industrial applications. The results show that considerable improvement over performance is achieved with respect to an event based networked control system.