Unknown input observer scheme for open-flow irrigation channels

Abstract

In agriculture, most of the water is transported by networks of open channel irrigation systems (OCIS). To ensure an optimal operation of this type of systems, it is very important to have accurate monitoring of all the system state variables. In order to perform robust estimation mitigating the effect of unknown user demands, an unknown input observer for one sided Lipschitz (OSL) quadratically inner bounded (QIB) systems is proposed. The proposed UIO scheme is assessed in a case study based on the Corning channel in California that is modelled uisng material and energy balances. The modeling methodology includes inflows and outflows of matter, along with a transition flow which models the effect of potential energy (channel slope) and kinetic energy (velocity in the transport of matter and frictional losses). The objective of this paper is to show that with the UIO for QIB-OSL systems, costs could be reduced in the purchase of sensors, since the observer is capable of reconstructing the upstream heights from the measurements of the downstream heights, which will be subject to noise and unknown inputs (in this case, user demands).