Research On Coordinated Motion Planning Of UVMS Under Uncertain Environmental Contact Force

The underwater vehicle-manipulator system(UVMS)consists of two subsystems:underwater vehicle and underwater manipulator.For UVMS to complete the established underwater task,it is necessary to coordinate the movement between the two subsystems.The coordinated motion between the carrier and the manipulator has the characteristics of strong nonlinearity,strong coupling and high redundancy,which makes the already complicated coordinated motion between the carrier and the manipulator more complicated and difficult to control.The nonlinear disturbance caused by the contact between UVMS and the environment in the underwater operation process has further improved the requirements for the operational accuracy and robustness of the robot control system.Therefore the development of a coordinated motion planning method of UVMS with high precision and high anti-interference ability has become the key research content of this paper.The main research contents of this paper are as follows:The kinematics and dynamics model of UVMS is deduced.A method of UVMS redundant analytical coordinated motion planning based on projection gradient method under the framework of task priority is proposed,which makes full use of the redundant degrees of freedom of UVMS to complete sub-priority tasks other than the first priority tasks,solves the problems of high redundant motion allocation,kinematic singularity and dynamic handling of multi-priority tasks of UVMS,and improves the working efficiency,coordination and flexibility of underwater operation of UVMS.A coordinated motion planning method of UVMS based on adaptive variable impedance control is proposed.Under the framework of task priority redundancy analysis,a redundancy analysis scheme based on projection gradient method is designed to minimize recovery torque,and a dynamic adaptive law is introduced to realize online dynamic coupling iterative adjustment of total impedance parameters.By solving the problems that the fixed impedance gain will cause system chattering under the action of continuously changing contact force and the expected trajectory tracking accuracy will be obviously reduced under the external nonlinear interference,the contact uncertainty between the UVMS end effector and the environment is estimated through the continuous online updating of impedance parameters and feedforward force control,which improves the robustness of the UVMS coordinated motion planning method under the large comprehensive uncertain nonlinear environmental contact force.An experimental platform of UVMS is designed,and the pool maneuverability experiment and trajectory tracking experiment are carried out,which verifies the feasibility of the overall coordinated motion planning of UVMS,and proves that UVMS can complete the underwater continuous maneuvering task more accurately under the proposed coordinated motion planning method.