Extended state observer-based fixed-time trajectory tracking control of autonomous surface vessels with uncertainties and output constraints

Abstract

A fixed-time trajectory tracking control of autonomous surface vessels (ASVs) subject to unmeasured speed is studied in this work. By using the homogeneity-based Lyapunov method, the unknown system states, including the unmeasured speed and lumped disturbances, are estimated by using a novel extended state observer (ESO) within fixed time. Subsequently, using the estimated states, the task of fixed-time tracking is completed with the aid of a newly proposed output-constrained power integrator method, which makes the vessel position and heading strictly within the predefined output constraints, and the tracking errors can be reduced to a range of zero under the continuous control action. The practical fixed-time stability (FTS) of the closed-loop system is analyzed in the sense of Lyapunov, while the output constraints can be well maintained during maneuvering. Finally, the ascendancy of the designed scheme is exhibited by simulation comparisons.

Keywords: Autonomous surface vessels; Fixed-time convergence; Output constraints; Output feedback.