The aim of this work is to present an application of recent methods for solving the l1 design problem, based on the Scaled-Q approach, on a high-order, nonminimum phase system. We start by describing the system which is an open-channel hydraulic system (e.g., an irrigation canal). From the discretization and linearization of the set of two partial-derivative equations, a state-space model of the system is generated. This model is a high-order MIMO system (five external perturbations w, five control inputs u, 10 controlled outputs z, five measured outputs y, 65 states x) and is nonminimum phase. A controller is then designed by minimizing the l1 norm of the impulse response of the transfer matrix between the perturbations w and the outputs z. Time-domain constraints are added into the minimization problem in order to force integrators into the controller. The numerical resolution of the problem proved to be efficient, despite of the characteristics of the system. The obtained results are compared in the time-domain to classical PID and LQG controllers on the nonlinear system. The results are good in terms of performance and robustness, in particular for the rejection of the worst-case perturbation.
Sharp Worst-Case Evaluation Complexity Bounds for Arbitrary-Order Nonconvex Optimization with Inexpensive Constraints
