Coupling dynamic analysis of underwater vehicle-manipulator system based on enhanced disturbance map

Underwater vehicle-manipulator system (UVMS) can be widely used in many marine fields, including seabed mining, fish farming, underwater vehicle docking, etc. However, the dynamics of UVMS are highly coupled, nonlinear and time-varying, and hydrodynamic parameters are uncertain and environment disturbances are unpredictable. The operation of underwater manipulator will obviously affect the position and attitude of underwater vehicle, as well as the precision of end-effector of the manipulator. Therefore, taking into account the coupling effect between the vehicle and the manipulator, a useful method for underwater manipulator planning is developed in this study. Firstly, a dynamic model of UVMS in the horizontal plane is established, considering both hydrodynamics and multi-rigid-body dynamics. By using UVMS model, the system behavior under various conditions can be predicted. Then, based on the principle of momentum conservation, the methods for generating disturbance map and enhanced disturbance map (EDM) of UVMS are given. Finally, a case study is conducted using motion planning and simulations, and the instantaneous values of disturbance by EDM theoretical analysis and dynamic simulation analysis are calculated. To evaluate the disturbance/coupling effect between the vehicle and the manipulator, a disturbance evaluation function is utilized. The results indicate that the EDM can represent coupling performance and effectively minimize the disturbance to the vehicle during manipulator operations. However, given the intricate working conditions of the UVMS, it is imperative to enhance the EDM method in future work by incorporating a diverse array of factors.