Output-feedback second-order sliding-mode control of uncertain linear systems with relative degree 2

A new output-feedback sliding-mode control scheme is proposed to deal with a class of relative-degree-2 uncertain linear systems. The controller is composed of linear filters and a single relay, without any real-time differentiators employed. Based on a specific characteristic of singularly perturbed sliding-mode systems, robust stabilisation, disturbance attenuation and asymptotic output tracking are also realised. Simulations show the simplicity and efficiency of this method.