Event-Triggered Networked Control Systems

Many of the results for event-triggered control of embedded systems can be extended to networked control systems. A networked control system or NCS is a set of controllers that coordinate their actions over a communication network. For NCS, event-triggering is used to decide when to transmit or broadcast the system state to a local controller’s neighbors. Using events to trigger communication actually provides a much stronger motivation for event-triggered control. The reason for this is that in many cases, the energy or cost associated with the transmission of a bit of information is much more than the energy associated with using that bit to compute the control law. Event-triggering, therefore, provides a realistic way of reducing traffic congestion in communication networks used by NCS. The objective of this section is to show how the earlier results from event-triggered control of embedded systems can be extended to networked control systems. The NCS architecture under study is first discussed and then we derive event-triggered triggers that assure input-to-state stability of the NCS. As in the case of embedded systems, the NCS implementation introduces a number of so-called network artifacts that complicate the analysis of the idealized model. These network models include delays in the transmission of information as well as dropped information packets. An important issue that should be addressed in the study of such systems is the impact that such network artifacts have on the overall performance of the NCS.