Research On Near-surface Motion Control Of Underactuated Underactuated Autonomous Underwater Vehicle

As the widest water body on the earth,the ocean is rich in oil,gas and mineral resources,attracting many countries and research institutions to carry out exploration activities.As the key equipment of deep-sea research,underwater vehicle has also attracted the attention of researchers,and the emerging autonomous underwater vehicle(AUV)has become the hot spot of current research due to its excellent navigation performance and relatively low price.For cruising AUV,although the reduction of propeller improves the endurance and navigation speed,it turns AUV into underdrive system,which brings a series of problems to the design of control system.At the same time,the strong non-linear characteristics of AUV under the constraint conditions and the problems such as the vulnerability to wave interference in near surface navigation also increase the design difficulty of control system.Therefore,it is of great practical significance to study the motion control of cruising AUV under wave disturbance.The main contents of this dissertation are as follows:Firstly,the six degree of freedom kinematic model and dynamic model of underactuated AUV are established respectively.The inertia force,viscous force,restoring force and control force involved in the dynamic model are analyzed and the calculation method is given.In order to facilitate the controller design,the six degree of freedom mathematical model is decoupled into the three degree of freedom mathematical model of vertical plane.The horizontal plane rotation and submergence of AUV are analyzed And the spiral submergence motion is simulated and its motion characteristics are analyzed to verify the correctness of the established model.Then,the dissertation analyzes the causes of the wave disturbance of AUV near the water surface,divides the wave force into the first-order wave force and the secondorder force,and analyzes the causes and characteristics of its formation;introduces the relevant wave theory,analyzes the factors affecting the effect of the wave force,and gives the specific calculation methods of the first-order and the second-order wave force;gives the control model of the sea wave force so as to The design of the observer,and the simulation analysis of the wave force calculation model and the control model.Then,the influence of the high frequency wave signal entering the control system is analyzed and the mathematical model of the three degrees of freedom vertical plane motion of the AUV in the discrete time domain is established.The Kalman filter theory and the traceless transformation theory are introduced.The design method of the wave filter based on the traceless Kalman filter theory is given,and the wave filter under different conditions of the AUV is established The output effect of the device is simulated.Finally,according to the dynamic characteristics of under actuated AUV,model predictive control is selected as the basic theory of AUV motion control method,and a vertical plane motion control system with wave filter is proposed.Aiming at the problem that the strong nonlinear characteristics of AUV make the calculation of control process too large,the state of AUV at the previous moment is selected as the working point,and the non-linear is treated by Stirling difference formula The system function is approximated linearly,and the linear model is used as the prediction model in the control process;the performance index function is constructed and rewritten into the quadratic programming form with the depth and longitudinal angle as the control objectives;the simulation experiment is carried out to verify the control effect and performance of the controller and the control system.