Pathfollowing And Trajectory Tracking Control For The Underactuated Autonomous Underwater Vehicle Under Current Disturbances

Along with rapid development of technology,economy and military use,more properties of autonomous underwater vehicles(AUVs)are required.The underactuated AUV is an underwater carrier with small size,good control ability,long endurance and strong carrying capacity,whose path following control and trajectory tracking control are important technical guarantee for the tasks of underwater exploration,environmental monitoring and sea area investigation.Therefore,path following control and trajectory tracking control for the underactuated AUV are representative and frontier topics.In this dissertation,we will study path following control and trajectory tracking control under current disturbances and design the robust control system for the underactuated AUV.Firstly,based on the complexity of the forces and the strong coupling of each freedom motion for AUV system,we consider the current disturbances and establish the AUV kinematics model and dynamics model.And the underactuated control system for difficulty and characteristics is analyzed.Then,towards the problem of 3D path following control for the underactuated AUV in the presence of parameter uncertainties and current disturbances,we establish the 3D error model based on virtual guidance method and Serret-Frenet coordinate.The robust controller for path following is designed based on the nonlinear damping backstepping control theory and the stability is proved by Lyapunov stable theory.Moreover,considering the influence of unknown current disturbances,the current observer based on the kinematic model is designed to estimate the unknown current.The sliding mode control that has invariance to the uncertain dynamics and external disturbance is succeeded to 3D path following control and stability is analyzed.Finally,to deal with the 3D trajectory tracking control problem of the underactuated AUV,the reference trajectory is planned and the information of reference trajectory is transformed into the velocity and pose of virtual target,which insure the rationality for the underactuated AUV trajectory tracking target.Moreover,the design form of the backstepping controller is simplified by defining the virtual speed error variable,and the singular problem in the process of solving control law is effectively avoided.In simulation,trajectory tracking control for the underactuated AUV 3D line and curve is achieved.