Holistic control system design for large mobile irrigation machines

Abstract

Large mobile irrigation machines are self-propelled sprinkler irrigation systems which farmers are rapidly adopting due to the high precision of the irrigation application. Although it is highly desirable that control systems be used with such machines to both optimise the irrigation water volume applied to field crops and optimise water use efficiency, there are difficulties in applying classical control techniques. These are caused principally by the very slow speed of crop growth-response and stress-response dynamics; but in addition characteristics of the plant and infield sensors which are poorly known and provide only sparse, low-quality data for feedback control. This paper outlines the operation of large mobile irrigation machines, analyses the limitations in the application of classical control approaches for their optimal use, and describes the methods that have been used to implement whole-system control via alternative (adaptive) approaches. These involve accommodation of sparse and unreliable input data and the application and evaluation of a range of irrigation volumes on different sub-areas of the field as on-the-go local system identification.