Research On Underactuated AUV Trajectory Tracking And Formation Control

The motion model of an underactuated AUV is a typical nonlinear system with strong coupling and non-integrity and is vulnerable to the unknown marine environment.It is difficult to design a controller with strong robustness and high tracking accuracy by using a conventional single nonlinear control theory.Therefore,the study of nonlinear theory in under-actuated AUV motion control has naturally become a representative frontier topic.In recent years,with the development of the marine economic strategy,the working mode of AUV has gradually evolved from a single operation mode to a cooperative formation operation mode.The AUV formation control operation can complete tasks that cannot be completed by a single AUV,such as coordinated operations,search and rescue,formation patrols.Etc.Therefore,AUV formation control has a strong application prospect.To this end,this paper takes under-actuated AUV as the research object.The main research is as follows:Firstly,the forces and moments acting on the AUV in the kinetic model are briefly analyzed,and the 6-DOF dynamics and kinematics model of the under-actuated AUV are established.Decoupling the model into two-dimensional horizontal plane and vertical planes from the aspect of strong coupling degree of each degree of freedom,and giving some basic concepts and theorems,paving the way for the subsequent research of trajectory tracking control method.Secondly,in the design of the conventional backstepping method,the design repeatedly controls the virtual control quantity,and there will be a "differential explosion",which leads to the complicated structure of the controller.In response to this problem,this paper designs an adaptive dynamic surface method.Firstly,the error equation is established in the Serret-Frenet coordinate system by using the desired trajectory and the current actual trajectory,and the trajectory tracking problem is transformed into the problem of calming surge velocity,yaw angular velocity and pitch angular velocity.Then the corresponding virtual control amount is designed and introduced.A first order filter is used to estimate the amount of virtual control.The"differential explosion problem" in the conventional backstep method is avoided,simplifying the design of the controller.Simulation experiments show that the designed controller can accurately realize the trajectory tracking of 2D horizontal plane and 3D curve.Then,based on the under-actuated AUV trajectory tracking problem with model uncertainty,an adaptive dynamic surface controller based on RBF neural network and fuzzy theory is designed.The approximation of RBF neural network and fuzzy theory is used to approximate the uncertainty existing in the model,and the adaptive dynamic surface method is used to solve the "differential explosion" in the derivation process.Furthermore,the accuracy and anti-interference ability of the controller are improved and the uniform chattering problem can be avoided better.The Lyapunov stability analysis proves that the closed-loop system is semi-global stable,and the simulation results show the effectiveness and feasibility of the controller.Finally,the formation control problem of underactuated AUV is studied.First,the adaptive dynamic surface controller is designed to enable the leader to track and track a time-dependent trajectory.Secondly,the concept of virtual leader is adopted for the follower AUV in the leader-follower model that cannot use the speed and angular velocity of the leader.Finally,based on the leader-follower formation control method,the underactuated AUV formation controller is designed to keep the followers in line with the follower.The Lyapunov stability analysis proves that the tracking error can converge to a small area near zero.The simulation results show the effectiveness and feasibility of the controller.