The intelligent message estimator for wireless network control systems

The data dropout and the time delay in networked control systems (NCS) degrade their performance greatly, especially under the wireless applications. In this study, both the message estimator and the traffic monitor designed for the wireless network control system (WiNCS) are proposed. Instead of the event-trigger NCS, the output feedback signal is sent by the timing trigger and the received node implemented with a message estimator for effectively compensating those lost data. Different estimators applied to the WiNCS have been discussed and results indicate that the Taylor estimator is preferred with easy implementation on a light-traffic network. Moreover, with the heavy-load network, the intelligent message estimator (IME) is suitable to cope with the unstable problem occurred in the Taylor estimator. Experimental results show that the Taylor estimator reduced the output error 30.1 % within a light-traffic network, and the IME reduced the output error 74.7% even with a heavy network load. Finally, when the network traffic is heavy enough, the sampling time of the WiNCS must be adjusted according to the data dropout rate based on the network traffic monitor to further decrease the dropout rate.