Path Following Control of Unmanned Surface Vessel Based on Fixed Time Control Strategy

This paper studies the path following problem of the underactuated unmanned surface vessel (USV) based on the fixed-time control strategy. First, based on the traditional extended state observer (ESO) line-of-sight (ELOS) guidance method, a new guidance law named improved ELOS (IELOS) is proposed with a variable look ahead distance, and IELOS includes surge velocity guidance law, which can make the system converge faster than ELOS guidance law; In addition, a fixed-time observer is designed for the lumped unknowns including model uncertainties and unknown environmental disturbances. Compared with the finite-time observer, the convergence time of the fixed time observer does not depend on the initial states of the system, and the convergence speed is faster; Finally, in order to achieve accurate tracking of the preset path, a controller based on fixed-time convergence is also designed to make the heading and surge velocity of the USV converge to the expected value calculated by the guidance law in a fixed time. The simulation experiment proves the effectiveness of the path following controller of the USV under the fixed time control strategy proposed in this paper.