Rigid-Profile Input Scheduling under Constrained Dynamics with a Water Network Application

The motivation for this work stems from the problem of scheduling requests for flow at supply points located throughout an automated network of open-water channels. The off-take flows are rigid-profile inputs to the system dynamics. In particular, the channel operator can only shift orders in time to satisfy constraints on the automatic response to changes in the load. This leads to a nonconvex semi-infinite programming problem, with a sum-separable cost that encodes the collective sensitivity of end-users to scheduling delays. The constraints encode the linear time-invariant continuous-time dynamics and limits on the state across a continuous scheduling horizon. Discretization is used to arrive at a more manageable approximation of the semi-infinite program. A method for parsimoniously refining the discretization is applied to ensure continuous-time feasibility for solutions of the approximate problem. It is then shown how to improve the cost without loss of feasibility. Supporting analysis is provided, along with simulation results for a realistic irrigation channel setup to illustrate the approach.