Wireless Event-Triggered Control for Water Irrigation Systems

Abstract

The application of optimal control structures for water irrigation systems (WISs) can be enabled by applying wireless event-triggered control (ETC). The term WIS, is used to describe open-water channels, that are mainly used to supply water to farmers all around the world. The water levels in these channels need to be controlled, but because of the large scale of WISs, it is very expensive to create centralized control structures when using wired connections between individual sensors, actuators and a centralized controller. Previously, WISs were typically controlled using individual decentralized (non-communicating) controllers. Applying wireless technologies enables communication between (smart) sensors, actuators and a centralized controller without the expense of installing and maintaining cables over lengths of kilometers. To create such a wireless infrastructure, a network needs to be designed, consisting of multiple nodes that are able to communicate with each other over wireless. Each sensor and actuator will be connected to (or integrated in) a node, just like the centralized controller needs to be connected to a node. To minimize the costs related to creating such an infrastructure, the nodes should have their own power source in order to prevent that a maintenance worker has to change the batteries of the nodes periodically. The nodes could be powered using a solar panel, or by using energy harvesting, which could be done by using a turbine to extract energy from the flow in a water channel. When using such energy sources, it is important to minimize the power consumption of the nodes. Most of the consumed power is used in communication when transmitting information. By applying ETC, the amount of communication between the individual parts of the control system is minimized, while still retaining good closed-loop system control using a centralized controller. In this research, techniques on wireless control, ETC and WIS control are combined and the application of an event-triggered centralized controller is presented using simulations, as well as the achievable reduction in communication compared to regular periodic control. Furthermore, a cyber-physical lab setup is designed and built which makes it possible to test these techniques in the Delft Center for Systems and Control (DCSC) lab.