Research On Path Following Robust Control For Underactuated Marine Surface Vessel

With the development of social economy and the continuous development and utilization of marine resources,the ship control technology has been greatly developed.In numerous key technology areas of ship,the path following control of underactuated marine surface vessel has become one of the research hot for ship motion control.The path following control system of underactuated marine surface vessel has the characteristics of under-actuation,strong non-linearity,vulnerability to model parameter changes and external environmental disturbances,and it is difficlut to improve the path following accuracy and anti-interference ability.Therefore,the research on difficult problems of the control system is helpful to improve the accuracy of path following operation,and has important practical application value.This paper motivitates to research the underactuated marine surface vessel and takes the model uncertainty,unknown external environment disturbances,time-varying sideslip,time-varying ocean currents,actuator input constraint,tracking error constraint and unknown velocity measurement into account the path following control,the problem of path following robust control for underactuated marine surface vessel is studied.The main research contents and specific research work of this paper are summarized as follows:Aiming at the problem of path following control for the underactuated marine surface vessel with model uncertainties,unknown external environmental disturbances,time-varying sideslip and time-varying currents,an improved line of sight-based(LOS-based)adaptive fuzzy path following control method is proposed.First of all,considering the effect of time-varying sideslip angle on the path following control of underactuated marine surface vessel,an improved adaptive LOS(IALOS)guidance law is proposed,which achieves the compensation of time-varying sideslip angle and improves the accuracy of path following.Secondly,the adaptive fuzzy path following controller is designed via backstepping method.And the tracking differentiator is introduced into the controller to obtain the differential term of virtual control law,which avoids the computational complexity of control law.The fuzzy system and adaptive technique are adopted to approximate the model uncertainties and unknown external environmental disturbances.And the robust path following control for underactuated marine surface vehicle is achieved in the condition of time-varying sideslip.Once again,further considering the effect of time-varying ocean currents on the path following control of the underactuated marine surface vessel,an improved adaptive integral LOS(IAILOS)guidance law is proposed,which can overcome the influence of time-varying sideslip angle and time-varying ocean currents on path following accuracy simultaneously,and then the accuracy of path following is improved.Afterwards,the adaptive fuzzy path following controller is designed based on dynamics estimator.The estimation error of estimator rather than the tracking error is used to update the fuzzy parameters.By adjusting the design parameters of the estimator,the estimation error converges faster,avoiding the limitation that the updating of the fuzzy parameters depends on larger initial tracking error,and improving the transient performance of the fuzzy system.Based on Lyapunov stability theory,it is proved that the path tracking errors of underactuated marine surface vessel can converge to an arbitrarily small neighbourhood around zero.In the end,the simulation results are carried out to demonstrate the effectiveness of the proposed path following adaptive fuzzy control approach of underactuated marine surface vessel.Aiming at the problem of path following control for underactuated marine surface vessel with model uncertainties,unknown external environmental disturbances,time-varying sideslip,actuator input constraint and tracking error constraint,an anti-saturation robust control method for path following is designed.First of all,considering error constraint problem,the Error Constraint Sideslip compensation-LOS(ECS-LOS)guidance law is designed by Barrier Lyapunov Function(BLF).The sideslip estimator is used to estimate the time-varying sideslip angle and the error constraints are not violated,which improves the path following accuracy.Secondly,the robust path following controller is designed via backstepping method and the disturbance observers are used to observe the unknown lumped disturbances of the system.In order to avoid actuator saturation occurence,the saturation compensator is introduced into the robust controller.The robust path following control of underactuated marine surface vessel is realized in the condition of time-varying sideslip,actuator input constraint and tracking error constraints.It is proved that the tracking errors can converge to an arbitrarily small neighbourhood around zero based on Lyapunov stability theory.Once more,in order to improve the path tracking performance and reduce the tracking time,a finite time LOS guidance law is designed based on the tan-Barrier Lyapunov function.The finite time sideslip estimator is adopted to estimate the time-varying sideslip angle in guidance law,which guarantees that the sideslip angle can be fast and accurately compensated.After that,the finite time path following robust controller is designed via backstepping method.The finite time disturbance observers are used to observe the unknown lumped disturbances of the system.To avoid the computational complexity of control law and satisfy the requirement of finite time convergence,the finite time tracking differentiator is designed to calculate the differential term of virtual control law.For the actuator’ s physical constraints and satisfying the requirement of finite time convergence,the proposed finite time saturation compensator is embedded in the finite time robust controller.It is proved that the tracking errors can converge to an arbitrarily small neighbourhood around zero based on Lyapunov stability theory and finite time theory.Eventually,the simulation results are carried out to demonstrate the effectiveness of the proposed robust control approach for path following of underactuated marine surface vessel with the actuator input constraints and tracking error constraints.Aiming at the problem of path following control for the underactuated marine surface vessel with model uncertainty,unknown external environment disturbances,actuator input constraints and unknown velocity measurements,an anti-saturation output feedback control method for path following is designed.To begin with,a third-order extended state observer is designed to simulataneously observe the vessel’s velocities and unknown lumped disturbances including the model uncertain terms and unknown environmental disturbances.In the next place,the velocity observation-based LOS guidance law and anti-saturation output feedback controller for path following are designed,which achieve path following robust control of underactuated marine surface vessel with the actuator saturation and unknown velocity measurements.Once again,in order to further improve the performance of path following control under the complex disturbance environment,a finite time extended state observer is designed,which can obtain the velocity informations and lumped disturbance informations of underactuated marine surface vessel in finite time.It is proved that the observation errors of finite-time extended state observer can converge to zero in finite time by homogeneous theory.Then,the velocity observation-based finite time LOS guidance law and the finite time path following anti-saturation output feedback controller are designed.According to the Lyapunov stability theory and finite time theory,it is proved that the tracking errors of underactuated marine surface vessel can converge to an arbitrarily small neighbourhood around zero in finite time.Lastly,the simulation results are carried out to demonstrate the effectiveness of the proposed anti-saturation output feedback control approach for path following of underactuated marine surface vessel.