Digital twin of USV thruster based on CFD simulations and towing tank experiments

Unmanned or Autonomous Surface Vehicles (USV/ASV), Remotely Operated and Autonomous Underwater Vehicles (ROV/AUV) are becoming widely used in industry, environmental monitoring and scientific research. In practice, it is often not feasible, or it is too dangerous to test and tune USVs equipped with expensive instruments and sensors particularly in high current environments. Realistic simulations are increasingly important, especially in hazardous operating conditions such as flooding river, catastrophe, bad weather conditions, heavy traffic, etc. The aim of this work was to create the digital twin of a 3D printed underwater thruster that is easily available and simple to manufacture. Transient Computational Fluid Dynamics (CFD) simulations were used to model the hydrodynamic forces acting on the thruster. This aims to enable the modelling of similar but different thruster geometries in the future, without the need for real experiments. In order to validate the CFD simulations and the final digital twin, open water propeller tests of the thruster were performed in a small towing tank. Underwater brake test bench measurements of the permanent magnet synchronous motor (PMSM) driving the thruster was also required to properly model the propeller-motor interaction. The validated thruster digital twin created in this paper can be used for realistic and safe simulations of USVs or can be run on an on-board computer for diagnostic and prediction tasks.