Sliding-mode control of uncertain systems in the presence of unmatched disturbances with applications

This article considers the development of constructive sliding-mode control strategies based on measured output information only for linear, time-delay systems with bounded disturbances that are not necessarily matched. The novel feature of the method is that linear matrix inequalities are derived to compute solutions to both the existence problem and the finite time reachability problem that minimise the ultimate bound of the reduced-order sliding-mode dynamics in the presence of state time-varying delay and unmatched disturbances. The methodology provides guarantees on the level of closed-loop performance that will be achieved by uncertain systems which experience delay. The methodology is also shown to facilitate sliding-mode controller design for systems with polytopic uncertainties, where the uncertainty may appear in all blocks of the system matrices. A time-delay model with polytopic uncertainties from the literature provides a tutorial example of the proposed method. A case study involving the practical application of the design methodology in the area of autonomous vehicle control is also presented.