Automatic Control of a Hydraulic Canal

Let us now turn our attention to the problem of the automation of water transportation processes, which are often implemented by means of open hydraulic canals. We will show how simple fractional-order PI controllers like those described in Chapter 5 can substantially improve the robustness of standard PI or PID controllers. Hydraulic canals are a typical example of dynamical systems with important delays and whose parameters may vary over a large range. Fractional-order controllers are designed that improve phase and/or gain margins — which are classical indices that measure closed-loop process robustness — while keeping the desired closed-loop behavior of the canal with the nominal dynamics. Moreover, it is shown that, for canals with significant and variable time delays, fractional-order controllers behave better than standard controllers when all of them are combined with the Smith predictor.