Stability analysis of networked control systems

We introduce a novel control network protocol, tryonce-discard (TOD), for multipIe-input-multiple-output (MIMO) networked control systems (NCSs), and provide, for the first time, an analytic proof of global exponential stability for both the new protocol and the more commonly used (statically scheduled) access methods. Our approach is to first design the controller using established techniques considering the network transparent, and then to analyze the effect of the network on closed-loop system performance. When implemented, an NCS will consist of multiple independent sensors and actuators competing for access to the network, with no universal clock available to synchronize their actions. Because the nodes act asynchronously, we allow access to the network at anytime but we assume each access occurs before a prescribed deadline, known as the maximum allowable transfer interval. Only one node may access the network at a time. This communication constraint imposed by the network is the main focus of the paper. The performance of the new, TOD protocol and the statically scheduled protocols are examined in simulations of an automotive gas turbine and an unstable batch reactor.