System Design And Motion Performance Analysis Of Lightweight Four-degree-of-freedom AUV

Topographical exploration in shallow waters,lakes and rivers is often carried out in an artificial form.Prospectors detect underwater terrain by diving,which is characterized by low efficiency and high risk.With the development of technology,underwater robots are widely used to explore the terrain.However,the current application is still a cable-type underwater robot,and the range of the robot movement is limited by the cable.Autonomous Underwater Vehicle(AUV)does not require communication cables and has better flexibility and autonomy.In this thesis,a lightweight and flexible AUV is studied to solve the problems of above exploration methods.In this thesis,the application requirements of the lightweight AUV are analyzed.And the design indicators of this AUV are proposed.According to these design indicators,the mechanical system and hardware system are designed,and the control program is written on the hardware platform to realize the stable operation of AUV.Considering the complexity and nonlinearity of the underwater environment,it is difficult to establish a control model of the AUV.In this thesis,the computational fluid dynamics software Fluent is used to analyze the hydrodynamic coefficients and fluid properties of the AUV systems.The relationship between the hydrodynamic coefficient and the speed is obtained,and the motion model of the robot is impro ved.At last,the better spacing of the dual AUV system is obtained.Based on the hydrodynamic analysis,the AUV ontology coordinate system and the world coordinate system are established.And the kinematics model and dynamics model of AUV are further obtained.Based on the models,the AUV depth motion model is derived.In this thesis,a nonlinear PID controller based on the target adjustment function is designed to control the depth motion of the robot.In this thesis,the controller is simulated by Simulink software to verify its effectiveness.In this thesis,four lightweight AUVs and one experimental pool are built to carry out various experiments.By indirectly measuring the relationship between the thrust and the travel speed of AUV,the correctness of the hydrodynamic simulation is verified.In order to verify the stability of the controller,the AUV deepening experiment and the deepening anti-interference experiment are carried out.The effectiveness and robustness of the controller are verified by the experimental results.Finally,the basic functions of AUV are verified by experiments.The experimental results show that the AUV has achieved the expected design requirements.