To address the cleaning requirements for marine growth on offshore platform jackets, an underwater cleaning robot featuring a combined “chassis + thruster-assisted adhesion + magnetic adhesion” mode is designed. The robot is equipped with four thrusters and a magnetic-adhesion wheeled chassis, enabling stable attachment and movement on varying-diameter pipes. Kinematic models in both inertial and body-fixed coordinate systems are established, and six-degree-of-freedom (6-DOF) dynamic equations are derived. These equations systematically incorporate key factors including added-mass forces, damping forces, hydrostatic restoring forces, ocean current disturbances, and thruster torques. Based on CFD simulations employing overset grids, moving reference frames, and simple harmonic motion techniques, the damping, added-mass, and thruster thrust and torque coefficients for each degree of freedom are identified. The obtained parameters demonstrate reasonable consistency with the CFD internal validation and preliminary external verification, providing a complete theoretical model and simulation data to support the motion control and operational stability analysis of the underwater cleaning robot. The established dynamic model addresses the free-navigation condition of the robot without cleaning operation. The additional hydrodynamic effects during cleaning operations will be considered in future work.
Sun et al. (2026) studied this question.