Research On Control Method Of Deep-sea AUV For Deep Diving Motion

Autonomous Underwater Vehicle(AUV)is an unmanned underwater platform that integrates artificial intelligence and other advanced computing technologies.Because the deep-sea area accounted for 89% of the total area,while the seabed contains a huge amount of resources,which makes the deep-sea AUV came into being.The motion control of deep-sea AUV deep submergence is an important technical foundation for the exploration of deep-sea area.It is of great significance for deep-sea AUV control theory and engineering practice to study the problems of deep-sea AUV deep submergence.In order to improve the maneuverability and control accuracy of deep-sea AUV,but also save the energy consumption of fixed depth navigation for the purpose of research,this paper focuses on the deep-sea AUV deep dive problem and the influence of the change of residual buoyancy caused by the change of sea water temperature,salinity and pressure on the accuracy of AUV fixed depth navigation.In this paper,under the interference of the residual buoyancy,carrying out related research on the deep-sea AUV deep dive motion control method and the application of the remaining buoyancy identification algorithm,the variable buoyancy system in the AUV fixed depth navigation.The main research contents are as follows:Firstly,the fixed coordinate system and the hull coordinate system are established.Combining the motion characteristics of AUV,the kinematics equation of AUV is established.Then,the force analysis of AUV is carried out,including the hydrodynamic force,the static force and the actuating mechanism,and the motion equation of AUV space six degrees of freedom is given with the knowledge of dynamics.At the same time,the influence of sea water temperature,salinity and pressure on the buoyancy of AUV is analyzed,and the model of deep-sea AUV buoyancy interference is established,which is based on the deep submergence of AUV.Secondly,aiming at the problem of nonlinear control and buoyancy disturbance motion control in deep submergence of deep-sea AUV,a backstepping trajectory tracking control method is proposed.This method adopts variable speed error method to design backstepping controller,ensuring that the deep-sea AUV under the influence of residual buoyancy,safety dive to the designated area in a specified time,while solving the singular value problem in the traditional backstepping method.In the MATLAB environment,the control effect of the control strategy is verified by simulation.Thirdly,for the problem of residual buoyancy when the deep sea AUV reaches thespecified depth,a new algorithm based on the Unscented Kalman Filter is proposed to estimate the residual buoyancy of AUV.This method can avoids the linearization of the nonlinear model,which preserves the high order terms so that it can more accurate model for buoyancy recognition,so as to improve the accuracy of the identification results,and to prepare for the high accuracy buoyancy balance adjustment.The effectiveness of the algorithm is verified in MATLAB environment.Finally,a one-way variable buoyancy system for buoyancy adjustment of AUV in deep sea environment is designed,and an AUV buoyancy equalization adjustment method based on residual buoyancy identification is proposed.Through the high-precision algorithm for residual buoyancy identification identifies the residual buoyancy of AUV fixed depth sailing,and then through balance system to balance the residual buoyancy,to eliminate the effect of residual buoyancy on the deep-sea AUV’s fixed depth sailing,to improve its handling and control accuracy,while saving energy consumption.In the MATLAB environment,the effectiveness of the method is verified.