Modeling And Control For Wireless Networked Control Systems Based On Communication Features Of Ieee 802.11

As an extension and development of the network control system, the wirelessnetwork control system inherits the advantages of structure networked, node intelligent,control scene, function distribution, open system and product integration. And it embracesincreasing applications in complicated industrial control fields, for its lower cost, morefree mobility, better extension and installation and maintenance convenience. But inwireless network control system the network resources are very limited and there existmore uncertainties. Therefore, communication delay, packet dropout and wrong packetsand some others problems are more stand out in wireless network control system. Theseproblems raise many new challenges in analysis and designs for a complex control system.Considering all these, we study the causes and characteristic of wireless networkdelay, packet dropout .etc of 802.11 protocol are studied in this paper. And then byintegrating the ideas of system control and network communication design, thecorresponding mathematic models、controller design and collaborative strategy ofscheduling-control design are also researched. The specific are as follows:First, the system modeling and control problem based on the wireless network controlsystem with both network-induced delay and packet dropout are considered. Consideringrandom of the system time-delays may be more than one sampling period and it isassociated with continuous packet dropout, so we introduce the event-based control theory,and present a linear system model. A sufficient condition is derived for the exponentialstability of the closed-loop system.Second, we propose a new dynamic control strategy with variable sampling periodfor wireless network control system with multiple control loops operating in 802.11．Thenew method can adjust the frequency of every sensor of each control loop according to theintegrated functions which comprise the status of delay and the error of state varietydynamically. The sampling periods are controlled to be based on the real-time availablebandwidth. Therefore, the overall control performance is improved significantly. Thestability analysis is provided by considering the characteristic of adaptive packet dropout method, and then control gain is obtained.Finally, according to the characteristics of the 802.11 protocol, we address anintegrated feedback scheduling scheme which is based on feedback control and networkscheduling co-design of Wireless Networked Control Systems with multiple control loops.The proposed method dynamically adjusts sampling the period and priority of the sensorof each control loop based on the integrated functions which comprise the status ofnetworked and the error of state variety and the consequence proves the performance ofoverall control.