Cross-layer Design Of Wireless Networked Control Systems

With the rapid development of wireless networks, wireless networked control systems are becoming a hot research direction in the control field. Wireless network has been widely used in the field of control for its characteristics of convenience, easy to maintain and broaden. Compared with wire networks, wireless networks are more susceptible to the environment. The transmission delay of data packets is longer, the probability of packet loss is bigger and the strictly hierarchical division of the network makes the limited network resources can’t be fully utilized. All these result in that the methods of designing wire networked control systems are hard to be applied in wireless networked control systems. In this case, an innovative theory--the cross-layer design of wireless networked control systems has been proposed.In this paper, focusing on the non-optimal and inflexible in the hierarchical design of traditional wireless networks, we design the controller and the wireless networks jointly and make the systems reach optimal performance. The main works are as follows:Firstly, the basic characteristics of wireless networks and some exist problems have been described in the introduction. The research progress of WNCSs are also introduced from the perspectives of control theory, communication theory and both control and communication theory, separately.Secondly, the basic concepts and applications of cross-layer design have been introduced. By analyzing the parameters that will affect control performance, the link layer, the MAC layer and the application layer are chosen to be the relevant layers of cross-layer design.Finally, the control systems are modeled as a Markov model. By using the principle of separation, the optimal state feedback controller with random delay and packet loss can be combined with the state estimator. The optimal output feedback controller with network parameters can be obtained at last. By adjusting the parameters in the given performance, we get that the optimal link design is QPSK and (15,11) BCH codes in32-bit frames, the optimal channel access probability is0.28and the optimal sampling period is6ms. Then the control systems reach optimal performance. The joint design of controller and network will be realized.