Abstract: Dynamic analysis and motion control of the 6-DOF underwater robot are researched. Firstly, considering the comprehensive influence caused by factors such as the gravity, buoyancy, driving forces, hydrodynamic forces, etc., dynamic equations of the underwater robot are established, which can describe the complicated underwater dynamic behavior of the robot. Then, in order to track the desired trajectory accurately, a nonlinear controller, which includes an outer loop and an inner loop, is designed using resolved acceleration method. In the outer loop, negative feedback is used to correct the deviation between the actual path and desired path. In the inner loop, based on the robot's dynamic properties, the nonlinear compensation is imported to simplify the robot system to a linear system and make it easier to control. Finally, simulations of the underwater robot tracking an object are taken. Simulation results show that the method can provide satisfactory tracking ability for underwater robots.

Key words: Dynamics, Motion control, Resolved acceleration method, Underwater robot