Research On Underwater AUV Docking System And Its Motion Control

Increasing pressure on necessary resources is motivating the human race to move to the sea to look for the storage of resources in the ocean.The need of marine exploration promotes the development of underwater vehicles.By improving the performance of the vehicle,we can exploit resources in deeper sea zone.For underwater vehicles,their endurance has a direct impact on the working range of them,which plays a decisive role in the realization of the offshore exploration.The traditional method of docking for underwater vehicle is time-consuming,and it is easy to cause mechanical damage due to the impact on the deck.Underwater docking technology makes it possible for the vehicle to execute direct charging operation and data exchange in the sea,which can reduces maintenance time,prolong the vehicle effective working time,and enhance the stealthiness of the vehicle.This paper introduces the design of the prototype of an underwater vehicle docking system which relies on a mechanical arm for orientation,demonstrate the prototype's motion scheme of underwater docking,establishes the prototype mechanical model in Solidworks,expounds the structure characteristics of the mechanical parts of the docking system,and introduces the experiment content of the shore simulation experiment for the prototype.In order to obtain the effective control commands to control the capture motion of the docking manipulator,the DH method is used to model the inverse kinematics to figure the relation between the the target position and the joint angles of the manipulator.Multiple solutions of inverse kinematics can lead movements of joints to a uncontrollable state,so we use the minimum stroke principle of inverse optimization to pick optimal solutions with the minimum amount of distances as input values of joint angle.Then link the results of inverse kinematics and the coordinates of the target position by structuring functions,establish the foundation for the subsequent dynamics analysis.Such a scheme can minimize the energy consumption of the motion mechanism and allow the docking manipulator to move to a predetermined position in a relatively short period of time.In order to search the solutions with minimum stroke among all inverse solutions more effectively,a clustering algorithm is proposed.In the rule of this algorithm,the angular samples of inverse kinematics will be classified,then the optimal scheme with minimum motion of joints can be found.The analysis of the dynamic of underwater docking system is conducted using Lagrange method,based on the working environment characteristics of the docking system.The inertia term,the gravity term,and the term of Coriolis force of dynamic equations are simplified,and the relationship of velocity and acceleration of rigid joints are deduced.Through this process,the model underwater docking system is built and the expression of function between the joint angle and joint torque,angular velocity and angular acceleration is obtained.Through the united simulation control system on the ADAMS-MATLAB platform,the PID control of joint independent movement and joint movement are simulated.Based on defects of PID control embodied in the control model,a fuzzy PID control algorithm is designed to improve the performance of control system.And the control results of the model of the underwater docking control system under PID control and fuzzy PID control are respectively compared,to verify that the fuzzy PID control system can achieve better performance.The prototype of underwater docking system is fully assembled,and the design and construction of the onshore experimental platform is completed.After those tasks,the prototype is installed on the experimental platform and the motion tests of the whole underwater docking system is completed.In the experiment,each joint can quickly response control command issued by the control handles,and the outputs of the actuators are functioning well and effectively perform scheduled action with stable operation.