The Study On Trajectory Tracking Control Of Underactuated Autonomous Underwater Vehicle

With the rapid development of economy and science technology,the ocean,which contains huge energy resources,especially the deep sea,has attracted more and more attention of all countries,and is also a hot spot of political and military attention of all countries.In the marine environment,the ocean current is complex and there are many uncertain factors.Autonomous underwater vehicle(AUV)has become an important tool to explore the ocean.It plays an important role in the research of marine environment detection and modeling,seabed search and underwater pipeline maintenance.The purpose of this paper is to study the horizontal trajectory tracking control of an underactuated autonomous underwater vehicle.First,based on the defined coordinate and the motion parameters of AUV,the kinematic model and dynamic model of AUV can be obtained.Considering the ocean current,the AUV model in the ocean current environment is further established.Second,aiming at the influence of constant ocean current on the tracking accuracy of AUV in deep-sea environment,based on Backstepping technology,a current observer is designed.The stability of the current observer can be guaranteed by adjusting the control parameters.The simulation results show that the designed current observer can effectively predict the current velocity and has stability.Third,backstepping technology is used to design the trajectory tracking controller.On the one hand,the sea current estimation is added into the virtual control law to improve the trajectory tracking accuracy;On the other hand,unlike the constant vertical virtual velocity control rate designed in previous literature,the vertical virtual control quantity designed in this paper changes with time,which can track the track with timevarying speed more effectively.The simulation results show that the designed controller is stable and has excellent tracking performance.Finally,aiming at the problem that the proposed backstepping trajectory tracking controller cannot solve the uncertainty of hydrodynamic coefficients and time-varying disturbances,this paper combines the adaptive control method and sliding mode control method,introduces the adaptive rate in the design of sliding mode function,and designs the adaptive backstepping sliding mode controller for AUV horizontal trajectory tracking.The adaptive backstepping sliding mode controller don’t need the accurate modeling and disturbance information and avoids the complex form of high-order derivatives in the control rate.The simulation results show that the tracking performance of adaptive backstepping sliding mode controller based on ocean current observer is better than the backstepping trajectory tracking controller based on ocean current observer.