Path Following Control Of The Underactuated AUV Based On Backstepping Sliding Mode

In recent years,the autonomous underwater vehicle(AUV)is widely used in modern marine development activities.Underactuated AUV model is highly nonlinear,and the movement has strong coupling between various degrees of freedom,Moreover,the model is vulnerable to uncertain interference,while there are input constraints.All of these factors complicate the path following control of underactuated AUV,which is challenging enough.First of all,we analyze the structure characteristic of the underactuated AUV,Meanwhile,we establish the kinematics model and and dynamics model of the underactuated AUV considering the hydrodynamic nonlinearity and coupling among degrees of freedom of underactuated AUV.According to the practical engineering,the model is simplified and decoupled for three degrees of freedom model in horizontal and vertical plane.Then,according to the analysis of the underactuated AUV nonlinear model,we obtain the derivation based on adaptive nonlinear sliding mode control and backstepping control.In the simulation experiments of velocity control,yaw control and depth control,we verify the validity of the model and the feasibility of the control method.Finally,based on the SF coordinate system,we establish path following error equations.In the following smooth curve which generated by virtual reference point,we choose the path parameter as an additional control,and adjust the rate to reduce the following error,meanwhile,we introduce the concept of approaching angle to improve the transient behavior of underactuated AUV when it converges to the expected path.According to the mentioned above,we design the kinematic controller and the dynamic controller to complete the simulation of horizontal,vertical,three-dimensional path following.We built the simulation model in SIMULINK platform,and simulations verify the effectiveness and robustness based on adaptive backstepping sliding mode.