Multivariable LQ control of an irrigation channel: Experimental results and robustness analysis

In this paper we consider LQ control of an irrigation channel where the water levels are controlled using overshot gates located along the channel. It is shown that a quadratic criterion as minimised in LQ control makes sense for the physical control problem at hand. Auxiliary states are included in the state space model in order to achieve zero steady state error and to avoid inducing large waves. The designed controller showed very good performance in a field test on a fully operation channel. The water levels recovered smoothly from disturbances without excessive oscillations, and the deviations from setpoints were small. The multivariable LQ controller attenuated disturbances as they travelled upstream and had better error propagation characteristics than decentralised controllers. Moreover, a robustness analysis showed that the controller is robust against input uncertainties and unmodelled high frequency dynamics