Research On UVMS Coordinated Control Method Based On Target Graspin

There are rich mineral resources such as oil and gas in the ocean,and more and more countries in the world pay attention to the exploitation of ocean resources.Underwater vehicle-manipulator System(UVMS)is an important Underwater equipment,now it is widely used in submarine pipeline laying and inspection,marine scientific investigation,military or civil underwater search and rescue projects.The main content of this paper is the research of coordinated control method for underwater target UVMS grasping.The realization of coordinated control mainly has the following difficulties:underwater environment of UVMS is complex and changeable and difficult to predict,so it is almost impossible to establish an accurate dynamic model of the system;UVMS is a kinematic redundant system,and there will be infinite solutions when inverse solutions are obtained by motion planning.There is dynamic coupling between underwater vehicle and manipulator,model uncertainty and unknown external disturbance,which will bring great disturbance to motion control.Based on the above difficulties,this paper carries out relevant research from three aspects of modeling,motion planning and trajectory tracking control,and the main research work is as follows:(1)Euler angle method was used to derive the kinematics equation of the underwater vehicle,D-H parameter method was used to obtain the homogeneous transformation matrix and Jacobian matrix of the manipulator,and the kinematics model of the UVMS joint space and the mission space was obtained from the kinematics model of the two subsystems.The space motion equation and the combined force/moment of the underwater vehicle are analyzed,and the dynamics equation is obtained.The Newton-Euler equation was used to model the dynamics of the underwater manipulator.Considering the dynamic coupling characteristics between the manipulator and the underwater vehicle,the coupling disturbance caused by the manipulator movement on the vehicle body was calculated.According to the two dynamic models,the force changes before and after grasping the target are further analyzed,and the dynamic models before,during and after grasping the UVMS target are obtained.In order to clearly describe the dynamics parameters of UVMS,in MATLAB/Simulink environment SimMechanics toolbox imported into Solidworks UVMS mechanical model,based on this UVMS 3D visualization dynamics model,and finally established the overall simulation model.(2)According to the redundant characteristics of the UVMS kinematics,the weighted pseudo inverse projection gradient method was proposed to carry out the UVMS motion planning.During the planning,the attitude Angle constraints of the underwater vehicle and the limit constraints of the joint of the manipulator were set,and the grasp trajectory of the manipulator was planned by using the quintic function curve method.The simulation results show that the proposed method can meet the task requirements and deal with the proposed joint constraints.(3)For trajectory tracking control problems of UVMS,such as dynamic coupling characteristics,model uncertainty and unknown disturbances,a quasi-sliding mode cooperative control strategy based on exponential reaching law was proposed for trajectory tracking control.The saturation function was substituted for the sign function to suppress sliding mode chattering,and the UVMS coupling dynamic model was established.The cooperative control method was used to treat the underwater vehicle and manipulator as a dynamic whole to counteract the coupling disturbance.By the simulation results show that the coordination control method for underwater vehicle manipulator and the coupling between disturbances have real-time compensation effect,and the control strategy is applied in UVMS performing the duty of fetching good joint trajectory tracking effect,at the same time can guarantee the manipulator end executor can track the desired trajectory and fetching to grab points.(4)A UVMS experimental platform was built,which was composed of a torpedo underwater vehicle and a four-dOF manipulator.The overall architecture design,mechanical structure design and electrical control system design of the platform are introduced,and the subsystem design scheme and debugging process of the control system are introduced one by one.In order to verify the coupling disturbance of manipulator motion to the vehicle proposed above,and to reflect the coupling compensation effect of the proposed controller,a dynamic coupling experiment between manipulator and underwater vehicle was carried out in a pool of water.In the absence of the control of the underwater vehicle,the joint of the manipulator moves with different trajectory.the coupling influence of the manipulator movement on the attitude of the underwater vehicle is obtained through the attitude data fed back by the attitude reference system in real time.