The Ratio Controller for Regulation of Turnout Flow Rate
2015
Stringam, Blair | Wahl, Tony L.
Setting and adjusting flow rates through turnout gates is a common task for canal operators and irrigators. When downstream flow measurement is available, the flow source is a relatively stable canal, and the turnout is controlled by a sluice gate for which flow rate is approximately proportional to gate opening, a simple ratio calculation can be used to estimate the change of gate position needed to reach a desired flow rate. This method can be used to estimate the next necessary manual gate adjustment or it can be incorporated into an automated ratio controller. The control method is analysed to demonstrate its stability and example applications are modelled to compare its performance to that of a typical proportional controller. The method generally performs as well as the proportional controller, with no need for empirical tuning. The one tuning parameter required by the method is the selection of a control cycle time. Cycle time is related to the settling time required for the canal reach between the turnout gate and the measurement device to attain equilibrium following a flow change. A design parameter for estimating a stable control cycle time is proposed.
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