Research On Three-Dimension Trajectory Tracking Control Of Underactuated Autonomous Underwater Vehicles

In recent years,autonomous underwater vehicles(AUVs)have been widely used in the fields of deep-sea mineral resources exploration,submarine cable inspection and underwater construction maintenance.AUVs need to navigate according to the desired three-dimension trajectories when they conduct submarine pipeline inspection operations,since the speed and the load of AUVs as well as the ocean environment are constantly changing,there are obvious uncertainties in the dynamics of AUVs and the environmental disturbances.In addition,in practical applications,most AUVs are underactuated due to the lack of direct propulsions in the transverse and vertical directions.When the AUVs are working in restricted sea areas,the actual trajectories of AUVs need to be limited in order to ensure safe operation.Therefore,carrying out the research on trajectory tracking control of AUVs and designing the robust and feasible trajectory tracking control law are conducive to the development of autonomous navigation systems for AUVs and localized equipment.It is of great theoretical significance and practical application value for realizing China's strategic goal of building a maritime power.In this paper,the mathematical model of the underactuated autonomous underwater vehicle(AUV)is established using Newton-Euler method.Then,considering the unknown time-varying disturbances problem of the underactuated AUV,a nonlinear disturbance observer is designed to estimate the environmental disturbances.The output redefinition method is used to deal with the underactuated problem of the AUV,and the backstepping method is used to design the three-dimension trajectory tracking control law to realize the three-dimension trajectory tracking control of the underactuated AUV.Next,in consideration of the dynamic uncertainties and unknown time-varying disturbances of the underactuated AUV,the output redefinition method is used to deal with the underactuated problem.The finite-time super twisting extended state observer(FSTESO)is designed to estimate the total disturbance combined by dynamic uncertainties and unknown environment disturbances,and then a finite-time robust control law is proposed combining with the super twisting sliding mode control to realize the three-dimension trajectory tracking control of the underactuated AUV.Further,in consideration of the output constraints,dynamic uncertainties,and unknown time-varying disturbances of the underactuated AUV,the output redefinition method is used to deal with the underactuated problem.An error mapping function is proposed to solve the problem of output constraints.Then a finite-time robust control law is proposed combining the super twisting sliding mode control with the FSTESO to realize the three-dimension trajectory tracking control of the underactuated AUV such that the trajectory tracking errors converge in a finite time and the actual trajectories remain within the desired constraints.The simulations of the three-dimension trajectory tracking control laws of an underactuated AUV are carried out using MATLAB/Simulink.The simulation results show the effectiveness of the proposed control laws.