Research On The Trajectory Tracking And Cooperative Control Of Unmanned Surface Vessels With Unknown Disturbances

As an intelligent tool for marine development,unmanned surface vessels(USVs)play an increasingly important role in many fields such as marine environmental monitoring,marine resource exploration,and offshore construction,and have become a hot spot in domestic and foreign research.As the marine operation tasks of USVs become more and more complex and larger in scale,higher requirements are put forward for the trajectory tracking control and formation tracking control performance of USVs.However,the dynamic model of the USV is extremely complex and difficult to accurately modeling.In the complex and changeable ocean environment,the USV will inevitably be affected by unknown disturbances such as ocean currents and wind and waves during the navigation process,which will seriously threaten the control performance of USVs,and the existing control strategy is difficult to take into account the influence of various factors that actually exist.It will face many challenges to realize advanced motion control.Therefore,in-depth research on the trajectory tracking and cooperative control strategy of USVs has important theoretical significance and application value.This paper mainly uses the BLF method,adaptive control,backstepping method and the neural network(NN)to study the trajectory tracking and cooperative control of USV under unknown disturbances.The main research contents are as follows:(1)For a class of USV system subject to unknown disturbance,a robust performance preset trajectory tracking control strategy based on BLF method is proposed.Firstly,a finite-time disturbance observer(FTDO)is designed based on the finite time control theory to estimate the external disturbance of the USV.Secondly,based on the BLF method,a constraint error virtual controller is designed at the kinematics level,which can limit the tracking error norm to a time-varying boundary range.Finally,combined with the designed FTDO,the corresponding robust trajectory tracking controller is constructed by using the backstepping method.The closed-loop system is proved to be stable by Lyapunov stability theory,and the effectiveness of the proposed robust trajectory tracking controller is verified by numerical simulation,and the tracking error is maintained within the preset time-varying boundary.(2)For a class of the USV system with uncertain external disturbance and unknown dynamic model,an asymmetric error limiting robust trajectory tracking control strategy based on adaptive NN is proposed.Firstly,in the kinematics layer,an asymmetric error-limiting virtual controller is designed by using an asymmetric BLF.Secondly,an adaptive NN estimation law is designed to approximate unknown nonlinear dynamics by using NN and the adaptive control method.Then,considering the robust control method,a robust compensator is designed to compensate the approximation error of the NN.Finally,the adaptive trajectory tracking controller is constructed by using the backstepping method combined with the designed asymmetrical limited error virtual controller,the adaptive NN and the compensator.The stability of the closed-loop control system is proved by Lyapunov stability theory,and the effectiveness of the proposed adaptive NN trajectory tracking control strategy is verified by numerical simulation.(3)For a class of the multi-USVs system suffering from complex uncertain dynamics,a cooperative control strategy of limited formation error based on BLF and self-organizing NN is proposed.Firstly,in the kinematics layer,the multi-agent consistency method is used to deal with the problem of the state information interaction transmission of each USV under the communication topology of the directed spanning tree.Then,the BLF method is used to restrict the consistency error within the specified time-varying boundary range,and a collaborative virtual controller is designed to limit the consistency error.Secondly,an adaptive and self-organizing NN is designed to estimate the composite uncertain dynamics of each USV by using a three-layer feedforward NN combined with an adaptive method and considering a self-organizing mechanism.Finally,a robust compensator is designed to compensate the NN approximation error and external disturbance.Based on the backstepping method and considering the design of the collaborative virtual controller,self-organizing NN and compensator,a multi-USVs cooperative formation controller is proposed.The stability of the system is proved by Lyapunov stability theory,and the effectiveness of the formation controller is verified by numerical simulation.