Path-Following Control Of Underactuated Autonomous Underwater Vehicle

In recent years,the motion control of autonomous underwater vehicle(AUV)has been widely 'used in various fields,especially in geological monitoring,energy exploration and pipeline inspection.Path-following control,as the basis of AUV's control,has received extensive attention from many scholars.However,in the real ocean environment,the application scenarios of underactuated AUVs are the most extensive.This thesis mainly studies the path-following control of underactuated AUV in.horizontal plane and three-dimensional space.The design method of the control law mainly adopts the backstepping method.The main research contents are as follows:1.For the path-following control problem of underactuated AUV in the horizontal plane,considering its external unknown disturbances,a finite-time path-following control law based on the "line-of-sight"(LOS)method is designed to realize underactuated AUV's curve path-following control.A finite-time disturbance observer is used to accurately observe external unknown disturbances,combined with the finite-time filter technology not only deals with the expansion problem of the.traditional backstepping method,but also solves the singularity problems in the control law design process.Considering the error caused by filtering,a filtering tracking error compensation mechanism is introduced to improve the control accuracy of path-following.2.For the path-following control problem of underactuated AUV in the horizontal plane,considering its external unknown disturbances,model uncertainties and the controller's input saturation,a finite-time path-following control law based on "line-of-sight" method is designed to realize underactuated AUV's curve path-following control.The control law is designed by combining backstepping integral sliding mode control with improved input saturation auxiliary design system,and using the second-order low-pass filter to obtain the first and second derivative of the desired heading angle to deal with the expansion problem of the traditional backstepping method.3.For the path-following control problem of underactuated AUV in three-dimensional space,considering its external unknown disturbances,model uncertainties and the controller's input saturation,a path-following control law based on "line-of-sight" method is designed.The radial basis function neural network is used to approximate the disturbances and model uncertainties.The control law is designed by combining the backstepping method and the input saturation auxiliary design system.Meanwhile,the dynamic surface technology is used to obtain the first derivative of the virtual control.In order to achieve more accurate path-following control,Super-twisting algorithm is used to accurately calculate the first derivative of the angle of sideslip and attack in a finite time.Finally,MATLAB simulation software is used to verify the effectiveness and robustness of the underactuated AUV's path-following control law designed above.The simulation results show the feasibility of the designed control law.