Research On Backstepping Sliding Mode Control Algorithm For Motion Of Underactuated AUV

As a strategic place for the peaceful development of the ocean,there is rich in marine energy and natural resources and it plays an important role in the national defense construction and economic development.As an advanced marine engineering equipment,autonomous underwater vehicle(AUV)has important signification and application value in marine resource exploration,maritime rescue and hydrological investigation.Underactuated AUV is a modern unmanned underwater vehicle with less control inputs than the number of system freedom.It has become the focus of research flied in the new generation marine control because of its advantages of small equipment weight,energy consumption and low cost.The main research contents of this paper are as follows:(1)The six degree of freedom spatial motion model of underactuated AUV is established,the hydrodynamic coefficient and parameter matrix in the system are analyzed,the highly coupled six degree of freedom spatial motion mathematical model is decoupled and simplified,the vertical and horizontal motion models are established.(2)The integral sliding mode control algorithm and backstepping method are used to design the fixed depth motion controller and horizontal track tracking controller.The stability theory analysis to prove that design is correct.The simulation experiments of different tracks in horizontal plane and depth control are carried out on the MATLAB simulation platform to verify the practicability of the research on the motion control of underactuated AUV based on backstepping sliding mode controller.(3)In view of the defect that the backstepping sliding mode controller designed in Chapter 3 is sensitive to external disturbance.Combined with the adaptive control method,the fixed depth motion based on external time-varying disturbance is studied and simulated,and an adaptive law is designed for the backstepping sliding mode controller.The control effect of the controller is compared under different disturbance.The comparative analysis shows that the controller is robust under external disturbance.(4)Aiming at the phenomenon that the control effect decreases of adaptive backstepping sliding mode controller when the external disturbance increases,a nonlinear disturbance observer is added to estimate the external disturbance,and the disturbance estimation value is feedback to the controller.An adaptive backstepping sliding mode fixed depth motion controller based on nonlinear disturbance observer is proposed.The controller studied in this paper is depth simulated and compared to fully illustrate the effectiveness and robustness of the controller.Finally,the field sea trial results are added to verify the practicability of the underactuated AUV depth motion controller in the actual sea area.