Computational Modeling of Trailing Operations by Autonomous Boat

The interest in autonomous marine vessels has been rapidly growing in recent years. Unmanned platforms are used for gathering data, performing inspection tasks, and serving as transportation means. In this study, a 3-DOF dynamics model, involving surge, sway and yaw, is applied for modeling a fast displacement-type hull. This model, utilizing hydrodynamic coefficients for the selected hull configuration, is employed for simulating autonomous operations. The boat actuators involve a propulsor and a rudder. A simulated set of autonomous operations includes several trailing scenarios. As a general pursuit algorithm, the constant-bearing method is utilized. Since the main objective for a pursuer is to approach a mobile target but remain at a desired relative position away from it, non-linear modulation of the desired relative speed is incorporated. Besides considering a target that moves with a constant speed along a straight line in calm weather, more complicated situations, such as oscillatory target trajectories and wind presence, are also investigated. A more challenging scenario, where the pursuer is required to change positions around the target with the purpose of inspection, is modeled as well. The selected control rules are found to perform well for all considered cases. The pursuing vehicle trajectories, relative velocities, and variations of the rudder angle and propulsor thrust are presented and discussed in the paper. In situations with the oscillating target trajectory and with variable desired position of the pursuer, the boat actuators have to work harder, reaching saturated states. The findings presented in this study can help engineers develop control algorithms for fast autonomous boats and select desirable hydrodynamic characteristics for hulls intended for autonomous trailing operations.