Research On Trajectory Tracking Of Underactuated AUV Based On Backstepping Sliding Mode Control

In the field of marine engineering,autonomous underwater vehicle(AUV)is an important tool for marine scientific investigation,marine target monitoring,deep-water exploration and offshore oil and gas exploration.AUV's motion control technology is the basis of its various tasks,and trajectory tracking is a hot topic in the field of motion control.In this paper,the tracking problem of underactuated AUV is studied with nonlinear control theory and method.The research focuses on the following aspects:Firstly,based on the references,the establishment process of motion control simulation model of underactuated AUV is described in detail.At the same time,the AUV motion model is simplified according to the characteristics of the research object.Then,the influence of various disturbances on the motion of underactuated AUV is analyzed,and the expression models of various nonlinear constraints are given.Finally,the motion and control characteristics of underactuated AUV are discussed.Secondly,based on the established motion model,a nonsingular fast terminal sliding mode control method with fixed time convergence is proposed for the two typical two-dimensional motion tracking problems of underactuated AUV,horizontal trajectory tracking control and depth tracking control.First of all,based on the research results of surface ship tracking,the virtual velocity control strategy is used to transform the position error stabilization control into the velocity error stabilization control.Then,the fixed time convergence fast terminal sliding mode is used to design the trajectory tracking and depth tracking controller,and the compensation control law is designed to compensate the parameter perturbation.Finally,the feasibility and stability of the controller are verified by numerical simulation.Thirdly,the research of underactuated AUV's plane trajectory tracking is extended,and the shortcomings are improved.To solve the problem of 3D trajectory tracking of underactuated AUV under the influence of model parameter perturbation and external current,a nonsingular fast terminal sliding mode control method based on nonlinear disturbance observer is proposed.First,the problem of error stabilization is transformed into a virtual velocity control strategy.In order to avoid the jump of virtual control quantity caused by position error in backstepping methods,the derivative of virtual velocity is obtained by dynamic surface technique.Then a tracking controller is designed by using the fast terminal sliding mode control,and the compensation control law is designed to solve the parameter perturbation problem.Next,a nonlinear disturbance observer is designed to observe and compensate the current disturbance.Finally,the effectiveness and robustness of the controller are verified by simulation.Finally,considering the more complex marine environment,an inverse step integral sliding mode control method based on linear extended state observer(LESO)is proposed for the 3D trajectory tracking control of underactuated AUV under the condition of model parameter uncertainty,external current interference and input constraints.At first,the problem of error stabilization is transformed into a virtual velocity control strategy,and the virtual velocity instructions are filtered dynamically.Then,the linear extended state observer is introduced to compensate the model uncertainty of the underactuated AUV system and the compound disturbance term caused by the external disturbance.And the auxiliary dynamic system is designed to solve the input constraint problem of the underactuated AUV.Finally,the effectiveness of the designed controller is verified by simulation.