  Event-triggered control (ETC) holds the potential to significantly improve
the efficiency of wireless networked control systems. Unfortunately, its
real-world impact has hitherto been hampered by the lack of a network stack
able to transfer its benefits from theory to practice specifically by
supporting the latency and reliability requirements of the aperiodic
communication ETC induces. This is precisely the contribution of this paper.
Our Wireless Control Bus (WCB) exploits carefully orchestrated network-wide
floods of concurrent transmissions to minimize overhead during quiescent,
steady-state periods, and ensures timely and reliable collection of sensor
readings and dissemination of actuation commands when an ETC triggering
condition is violated. Using a cyber-physical testbed emulating a water
distribution system controlled over a real-world multi-hop wireless network, we
show that ETC over WCB achieves the same quality of periodic control at a
fraction of the energy costs, therefore unleashing and concretely demonstrating
its full potential for the first time.
