The Integrator Dual-Delay model for advanced controller design of the open canal irrigation systems with multiple offtakes

[Display omitted] •The unrealistic offtake assumption of the Integrator Delay model is analyzed for the first time.•The Integrator Dual-Delay model is developed by innovatively considering the offtake flow delay.•Centralized model predictive controllers are designed for cascade canals with multiple offtakes.•The Integrator Dual-Delay model remarkably enhances the water level control stability. The Integrator Delay (ID) model is widely used for advanced controller design in canal automation projects, assuming that all offtakes are aggregated into one at the most downstream end for each canal pool. However, such an unrealistic assumption differs greatly from the actual location distribution of the offtakes in most open canal irrigation systems (OCIS), leading to increased uncertainties and inaccurate canal operations. For this reason, this study introduced the Integrator Dual-Delay (IDD) model, capable of innovatively considering the lag-effect of the offtake flow changes alongside the irrigation canal. To investigate the effectiveness of the modified control-oriented model in upgrading the canal automatic operating systems, two centralized model predictive controllers were designed with the ID model and the IDD model, respectively. Then the simulation tests were carried out on the Third Main Canal of the Zhanghe Irrigation System in Southern China. Two performance indicators of Non-dimensional Integrated Square of Error (NISE) and Non-dimensional Integrated Square of Discharge Change (NISQ) were adopted to measure the water level control stability and flow control stability. The results show that with the IDD model, the NISE is reduced from 3.53 × 10-5 to 1.88 × 10-5 and the NISQ is reduced from 3.23 × 10-6 to 2.88 × 10-6, indicating that the proposed IDD model can help the control stabilities of water level and flow to be improved by 46.7 % and 10.8 %, respectively. The IDD model constructs a more accurate state-space prediction process for advanced controller design and contributes to more efficient canal automatic operations, showing great potential in precision irrigation for various OCIS.