| As humans attach importance to marine resources,Autonomous Underwater Vehicles(AUV)have gradually shown their importance.AUV recycling is an effective way for AUV to achieve working life and data exchange.Through the connection between the AUV and the underwater recovery mechanism,the AUV can be replenished in time before the energy runs out,and the collected data is uploaded in time for data exchange.The accurate path tracking capability of the underwater robot is one of the technical guarantees of the AUV's underwater operation capability.The marine environment is extremely complex and full of uncertainty.In actual operation,due to its strong non-linearity,uncertainty,and multi-coupling characteristics,when the operating speed and operating environment change,the hydrodynamic and inertial forces experienced by the AUV Coriolis centripetal force will change accordingly,and it is difficult to establish an accurate dynamic model to track its trajectory.In the process of AUV recovery and docking,due to the error of path tracking and the interference of the external ocean current environment,the AUV collides with the docking device.Under this condition,this paper studies the collision between the AUV and the docking device,analyzes the impact force,and studies the factors affecting the collision force through the simulation of virtual prototype,and then studies the AUV precise path tracking control algorithm to avoid collision between AUV and docking device.The specific research contents are as follows:(1)The research status and development trends of AUV recovery docking system,ship collision and AUV path tracking control algorithm at home and abroad are analyzed,and AUV dynamics model is established.(2)Mathematical modeling and analysis of the collision between the AUV and the docking device.The related theories of contact collision are introduced,and the methods of theorem of momentum,theorem of moment of momentum,recovery coefficient method and equivalent spring damping model are analyzed to calculate the magnitude of the collision force and the movement of the object after the collision.(3)ADAMS software is used to perform dynamic simulation analysis on the collision process between AUV and guide hood,and study the impact of the four factors on the collision process: AUV initial velocity,guide hood opening angle,eccentric distance between AUV and docking device,and the deflection angle between the AUV center and thecenter axis of the docking device.The corresponding maximum collision force is obtained,and the matters needing attention in the actual docking process are analyzed.Finally,based on the simulated data,multiple regression equation is used to obtain the regression equation between the maximum collision force and the initial speed of the AUV,the opening angle of the guide hood,the eccentricity between the AUV and the docking device,and the deflection angle between the AUV center and the center axis of the docking device.To provide a reference for later optimization of the actual docking device.(4)Aiming at the path tracking problem of autonomous underwater vehicle in the process of docking,a fractional order sliding mode control algorithm based on RBF neural network is proposed.Firstly,the sliding mode control is used to track the path,the fractional calculus is introduced into the constant velocity approach law of sliding mode control to alleviate the shaking of the system.Then the RBF neural network is used to compensate for uncertainty in the AUV motion model and the external interference.Finally,the stability of the control system is proved by Lyapunov stability theory.The simulation results show that the designed controller can effectively track the path of AUV.By comparing the tracking effects with traditional sliding mode control and fractional order sliding mode control without considering system uncertainty and external interference,it is proved that the control method has faster tracking speed,better stability and better tracking performance. |
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