Research On The Three-dimensional Trajectory Tracking Of Underactuated Autonomous Underwater Vehicle Under Current Disturbance

Autonomous Underwater Vehicles(AUVs)have been playing an increasingly important role in the area such as search and rescue,military and ocean development etc.Trajectory tracking control of underactuated AUVs is one of the most significant problem in the issue of AUV motion control.This paper addresses the problem of regulating the dynamic model of a nonholonomic underactuated autonomous underwater vehicle(AUV)to a curve with a desired orientation.In the first place,the three parts of marine craft motion control is specified.Meanwhile,this paper also explains the reason why the underactuated AUVs are more attractive than their full actuated counterparts and some typical underactuated AUVs are introduced.After the kinetic model of the underactuated AUV being analyzed,the model is divided into two parts,i.e.the actuated part and the underactuated one.The nonholonomic property of underactuated constraint function is strictly proven,meanwhile,the controllability of that function is discussed in this paper.All those mentioned above lay realistic foundation for realizing the 3 dimension trajectory tracking of the underactuated AUVs under ocean current.On the other hand,a control method-backstepping control method is presented in the next section,not only the history of this method is illustrated but also the mathematics structure is described.Moreover,on the condition of only the linear hydrodynamic coefficients exist,a cascaded system is introduced and a new time-variant stabilization theory is adopted to come up with the control method.What is more,the range of the control factors are chosen according to that theory.Simulation test by Simulink was conducted and the result strongly supports the control method.In order to describe the real situation,the damping matrix should be contained the second order hydrodynamic coefficients,which totally changes the problem.So a new control law based on backstepping method and Lyapunov stabilization theory combined with the Line of Sight(LOS)technique was employed.Simulation shows a satisfying result.Considering both the advantages and disadvantages of the control methods mentioned above,a new method also based on backstepping is put forward,and simulation testify the effectiveness of this controller.At last,this paper pays attention to the ocean current disturbance which is the main influence to the quality of the AUVs’ tracking,and a dynamic structure in which the current influence is regarded as a kind of disturbance,all that mentioned above lay a solid foundation for current oberserver.