Decentralised Hierarchical Multi-rate Control of Large-Scale Drinking Water Networks

We propose a decentralised hierarchical multi-rate control scheme for the control of large-scale systems with state and input constraints. The large-scale system is partitioned into sub-systems each one of which is locally controlled by a stabilizing linear controller which does not account for the prescribed constraints. A higher-level controller commands reference signals at a lower uniform sampling frequency so as to enforce linear constraints on the process variables. Worst-case subsystem interactions are modeled and accounted for in a robust manner. By optimally constraining the magnitude and rate of variation of the reference signals to each lower-level controller we prove that closed-loop stability is preserved and the fulfillment of the prescribed constraints is guaranteed. We apply the proposed methodology for the decentralised control of a quadraple-tank system, known as Johansson’s system and we compare it to a centralised control approach.