Multi-hopping induced gain scheduling for wireless networked controlled systems

A multi-hopping induced gain scheduler for Wireless Networked Controlled Systems (WiNCS) is proposed. The control scheme is based on a client-server architecture. The data packets are assumed to be carried over a network composed of wireless sensor nodes running the 802.11b protocol. The number of hops necessary for packets to reach their destinations is variable and depends on current traffic conditions. Changes in the number of hops induces changes in the latency times introduced by the communication network in the feedback loop. To deal with these changes an LQR-output feedback scheme is introduced, whose parameters are adjusted according to the number of the hops. The weights of the LQR controllers are subsequently tuned using LMIs to ensure a prescribed stability margin despite the variable latency times. The overall scheme resembles a gain scheduled controller with the number of hops playing the role of the scheduling parameter. Simulation results on the NS-2 simulator are provided to highlight the efficacy of the proposed scheme.