A fixed-time distributed formation control of marine surface vehicles with actuator input saturation and time-varying ocean currents

Abstract

This paper designs an anti-saturated fixed-time distributed formation control law for marine surface vehicles (MSVs) with unmeasured velocities, model parametric uncertainties, actuator input saturation and environment disturbances caused by wind, waves and ocean currents. Initially, model parametric uncertainties and environment disturbances are considered as compound disturbances, and a fixed-time extended state observer (FxESO) is proposed to provide the simultaneous estimation of the unmeasured velocities of MSVs and compound disturbances in fixed time. Furthermore, in order to reducing the influence of time-varying ocean currents on the navigation of MSVs, a novel fixed-time ocean currents estimator (FxOCE) is presented to precisely identify it at the kinematic level in fixed time. Additionally, under the circumstance that only one MSV can receive the desired position information, based on the estimation values, an anti-saturated fixed-time distributed formation controller is designed to track the desired formation. Subsequently, a saturation function is integrated with the formation control law to resolve the actuator input saturation problem. Then, by using homogeneous theory and fixed-time stability theory, it can be proved that the closed loop formation control system is fixed-time stable. Finally, comparative simulation results show the effectiveness and superiority of the proposed anti-saturated fixed-time distributed formation control scheme.