System Identification and Control of an Irrigation Channel with a Tunnel

The demand on water is high but the supply of water is low due to the dry and warm climate in Australia. This is especially difficult for farmers that do not get enough water delivered in the irrigation channels which has dramatic consequences. A high percentage of the water lost in the channels can be saved if the systems are managed better. Using system identification techniques to develop a mathematical model which describes the dynamics in the irrigation system is a helpful tool for control system design. The model needs to be able to describe the downstream water level of a pool, containing a tunnel, in a satisfying way. The model was built using data from experiments to estimate unknown parameters in a chosen model structure. A feedforward PI controller with a low pass filter was designed using frequency response techniques and the results were simulated with varying parameters and disturbances. The result of the modeling was a first order OE grey box model. The model performed well on validation data and was therefore used in the controller design. The controller using both feedback and feedforward could in a satisfying way reduce offtake disturbance, track water level set points and limit the excitation of waves in the channel, and therefore also reduce the water wastage