Output feedback second-order sliding mode control of the cart on a beam system

We propose an output feedback second-order sliding mode controller to stabilize the cart on a beam system. A second-order sliding mode controller is designed using a Lyapunov function-based switching surface and finite-time controllers, while the state estimator is designed based on the Luenberger-like observer. The proposed observer extends the applicability of Luenberger-like observer to nonlinear systems that are not input-output linearizable, but can be approximately input-output linearized. The approximation is based on the physical property of the system, wherein certain terms in the total energy are neglected. Extensive numerical simulations validate the robustness of the proposed controller to parametric uncertainties using estimated states. © 2009 John Wiley & Sons, Ltd.