Modeling And Control For Wireless Networked Control Systems Based On IEEE 802.11b

Wireless Networked Control Systems (WNCS) is the production of the cooperation of wireless communication technologies and control theories. Compared with wired networks, wireless networks are gaining increasing applications in industrial control fields with lower cost, more free mobility, better extension and the convenience during installation and maintainance. However, as bandwidth and transmission power are limited and the uncertain paths in wireless networks, delays, packet dropouts and errors are more likely to take place. Fortunately, as wireless networks based on the WLAN criteria IEEE 802.11b are with great transmission distances, credible capacity for data transmission and the excellent function of collision avoidance, it is widely studied and applied in the synthesis and analysis for WNCS. In this paper, the causes and characteristic of network delays, packet dropout, wrong packets or sequence and quantized effects based on protocol 802.11b are studied, and the corresponding mathematic models are constructed, the controllers are also designed to consider the performance of the WNCSs.This paper firstly proposes the idea of modeling WNCS on current popular network protocols IEEE 802.11b. The firstly built WNCS model considers delays, dropouts and quantized effect under various kinds of network conditions. For the uncertainty of network delays and the quantization error, guaranteed cost controllers are designed to stabilize the system and make it achieve certain cost values.Later, for the ignorance of the distinction between network delay and packet dropout in most of the current research on the modeling for WNCS, we design a new network structure based on 802.11b to distinguish them two clearly. The corresponding WNCS model considers not only all the network effects, but also packet error and wrong sequences. The designed controller makes the system globally mean-square asymptotically stabilized (GMSAS). Lastly, as most of the current methods on WNCS either focus on the control system and ignore the effect of networking, or vice versa, we consider both the two effects and design a controller based directly on the networking to stabilize the system. Not only is the proposed network scheduling suitable for controller design, it also shows some advantages compared with current widely using scheduling methods. Simulation results show the merits of the scheduling-based controller.