Research On Network Delay For WiNCS Based On Fuzzy Deadband Scheduling Methods

The Wireless Networked Control System(WiNCS) is a complex distributed control system which combines the wireless control theory and modern wireless communication technology. Wireless Network has been widely used in the field of large-scale control system for the sharing of wireless communication channel resource. Compared with traditional control system which is connected by point-to-point cables, the WiNCS is more adaptively to the environment for the advantages of the less wiring, low cost, easy to maintain and broaden.However, with the using of wireless communication network, the problems such as the Network-Induced delay, node competition, packet dropout and power control appear. It is well known that Network-Induced delay and packet dropout are the source of instability, and which can degrade the control performance, especially the WiNCS transmission delay of data packet is uncertainty. So it is significant to develop the research of network delay for the application and design of WiNCS. Following the analysis of the influencing factors for Quality of network Service(QoS), a new data scheduling algorithm for reduceing the NetworkInduced delay is proposed in this dissertation.Firstly, the selected topic background and research significance of this project is introduced, and the main research idea of the experts and scholars home and abroad in recent years are compiled, and the current research status of Network-Induced delay is introduced, then the main research work in this dissertation is summarized.Secondly, the structure and network topology and the data transmission of WiNCS are analyzed deeply, and the mathematical model of WiNCS with delay is proposed. Then the measurement methods and composition of Network-Induced delay are analyzed. Based on the design of mathematical model of WiNCS with Network-Induced delay, the simulation of WiNCS is completed. The simulation results show that Network-Induced delay have a serious impact on the system specifications, such as overshoot and adjustment time. the Deadband method action principle of WiNCS and Network-Induced delay affected by deadband in data transmission are analyzed. The mathematical analysis results show that Network-Induced delay can be reduced by the Deadband method.Thirdly, Deadband method of WiNCS reduced control accuracy, so the Fuzzy Deadband Scheduling Method is proposed for this deficiency. According to the output difference of system and Network Congestion, deadband threshold is setted up. Fuzzy Deadband Scheduling Method adjusts network load variation amount timely, and in order to capture the network traffic variation and Network Quality of Service, the Fuzzy Deadband Scheduling Method automatically reduces the amount of data packet transmission within the permissible error. Experiments show that the method can reduces the packet transmission amount, and effectively guarantees system control accuracy. Fuzzy Deadband Scheduling Method is simple and easy to implement. The method has been achieved a high level of technology requirements and good effectiveness.Finally, in order to verify the effectiveness of this algorithm, the multi loop Wheeled Mobile Robot(WMR) simulation connection diagram of WiNCS has been setted up by TrueTime 1.5 Toolbox. The simulation results show that Fuzzy Deadband Scheduling Method can reduce delays and improve Performance of Control System, and WMR trajectory tracking has good effect.