Stability and feedback control of wireless networked systems

This study analyzes data losses and their effect on wireless networked system stability/performance using a simple communication scheme and a stochastic 2-state Markov network model. An architecture utilizing event-driven control and clock-driven, co-located sensing and actuation serves as the base framework. Data losses are treated in a switched system scheme where two discrete dynamics are available. When the network transmits data successfully, the closed loop dynamics are active; when packets are dropped, zero control is applied and open loop dynamics exist. Using analysis tools for stochastic stability of Markov jump linear systems, operating conditions in a probability space can be identified for given plant dynamics that ensure second moment stability (SMS). Additionally, switched system H_∞ norms can be used to identify regions of network operation in the probability space with expected levels of performance. Results from these tools and experiments involving wireless hardware suggest a scheme for decentralized controller variation that rebalances network loading for the control loops when communication disturbances occur in the network. This scheme varies the sampling period of the individual loops based on network condition measurements, system stability/performance requirements, and computation/bandwidth limits of the hardware.