A Novel Fixed-time Observer-based Sliding Mode Controller for Nonlinear Underactuated Hovercraft

Using information from the state observer to the controller in real-time is an open field for research and fundamental for solving many problems in control theory. Control of underactuated systems is challenging since the degree of freedom (DOF) of these systems is more than their control inputs. In this paper, a fixed-time sliding mode controller for nonlinear underactuated hovercraft systems and a fixed-time sliding mode observer are described. The estimated states of the observer are used in the controller in real-time. The controller and observer work together to track the hovercraft's desired trajectory and estimate the states of the hovercraft. The observer and controller are chattering-free, fast-tracking, and smooth controlling. The Lyapunov theory is used to prove the controller's stability and the observer. The performance of the algorithm is demonstrated in a simulation example.