Delay Compensation And Control Of A Networked DC Motor

Networked Control System (NCS), i.e. Network-based Control System, is a control system architecture in which all control system components are connected together to build feedback control loops by a real-time network.Compared with traditional centralized point-to-point control systems, networked control systems provide several advantages such as reduction of wiring and cost, easy installation and maintenance, high reliability and flexibility. But networks also bring several new problems to control systems, among which network-induced delay and data packets dropout are the most important ones. Without proper consideration, network-induced delay can degrade the performance of control system and even destabilize the system. Data packets dropout also can influence the system performance greatly.In this thesis, the delay characteristic of Ethernet is analyzed. Then a simplified delay model of Ethernet is built under several assumptions. A delay compensation scheme based on Levinson predictor is proposed. The predictor provides p steps ahead prediction of the plant output to controller so that the delay effect on system output can be compensated. The estimation of Levinson predictor's parameters and ordering is also introduced. A networked DC motor is picked as an example to illustrate the efficiency of the delay compensation scheme. The simulation results show that the Levinson predictor based delay compensation scheme reduces the delay effect on system and makes system settling down quicker. Limitation of the Levinson predictor based delay compensation scheme is analyzed. A simulation model of the network with packets dropout is built and the performance of networked DC motor with data packets dropout is given. The thesis concludes with the future works.