A Framework for Modeling Underwater Vehicles in Modelica

While developing Remotely Operated Vehicles (ROVs), repeated construction and field testing ROV designs and control strategies is logistically difficult, time-consuming and expensive; mathematical models have become extremely useful tools that aid this process. This paper's goal is to demonstrate an application of a modeling framework built in Modelica for developing such models of underwater ROVs. Named the Underwater Rigid Body Library (URBL), the framework addresses the modeling of underwater vehicles in two distinct parts - addressing rigid body dynamics underwater as interactions with a field of water, and providing a basic propulsion mechanism, based on a generic underwater propeller. This paper extends the work described in [1] by focusing on comparing the constructed model against experimental data. Experiments were conducted in a pool setting; raw motor command data was extracted and used to control the model. The ROV's motion from the experiment and the simulation were compared - the results of the comparison indicated the simulation's motion profile was similar to that of the experimental results.