The energy benefit of level-crossing sampling including the actuator´s energy consumption

When using level-crossing (also called send-on-delta) sampling in control loops, messages can be saved compared to periodic sampling without degrading control performance. While it is clear that reducing messages improves also the energy efficiency of battery-powered sensor devices, this can be disadvantageous for the energy efficiency the actuator device. This paper addresses the question, under which conditions level-crossing sampling is also for the actuator device more energy-efficient than periodic sampling. It is shown that there is an optimum inter-sample interval. Methods for reaching this optimum by appropriate controller and transmission settings are given. The theory is demonstrated using several known, standardized wireless network protocols.