Research On UVMS Attitude Control Method Under Working Conditions

Underwater Vehicle-Manipulator System(UVMS)is a fully automatic and flexible system to perform diverse and sophisticated operations under the water such as marine survey,salvage diving,maintenance and recycling of subsea equipment,and sampling of marine life.UVMS is a strongly coupled,nonlinear and time-varying system.The underwater operation of the manipulator will greatly affect the attitude of the body,resulting in the failure of the task.This article analyzes the coupling of the UVMS system and undertakes the research into the attitude control during the operation.Firstly,an experimental platform for under-actuated underwater vehicle and four-degree-of-freedom underwater manipulator UVSM is established.After debugging each subsystem,a small pool was created to study the basic movements of UVMS,and the data about the attitude change of the Autonomous Underwater Vehicle(AUV)when the manipulator is working under certain circumstances is collected to provide experiment data for subsequent coupling analysis.Secondly,the AUV dynamics model is constructed by deriving kinematics model,analyzing the movement equation,rotation equation and force condition.The kinematics model of underwater manipulator is established by applying the Denavi-Hartenberg(D-H)parameter method.The dynamic model of the underwater manipulator is derived by using Lagrange equation.The overall mathematical model of UVMS is built on the basis of the interaction of the two subsystems.Thirdly,an adaptive switching learning PD control method is proposed for the joint space control of the underwater manipulator system.To minimize the uncertainty and random interference of the model operating below the surface of water,a new method is devised.Robust control is introduced into the controller,and the effectiveness of the controller is verified through simulation analysis.Taking the contact of the operating task with the environment into account,a single parameter-based adaptive sliding mode impedance control method is proposed.It is verified by simulation that the end of the manipulator can track the trajectory of the desired impedance quickly and stably,while the contact force of the end of the joint is within a reasonable range.Finally,the coupling effect of the manipulator's movement on the underwater vehicle is analyzed,and the constraint force of the manipulator base on the body is obtained through the Newton-Eular formula.The influence of restoring torque is clarified by analyzing the change of the center of gravity and buoyancy of the underwater manipulator;the water resistance is calculated by Morison formula.According to the dynamic equations of the vertical plane of the system and the coupling effects between the systems,a mathematical model of the under-actuated underwater vehicle is established.After the control research of the vertical plane attitude under working conditions,a fuzzy adaptive backstep controller is designed.The Lyapunov theorem is utilized to prove the stability of the designed control system,and the attitude is verified under different motion conditions through simulation.