Experimental Evaluation of Error-Dynamics-Based Trajectory Tracking for a Torpedo-Type AUV with Thrust Vectoring

This study implements an error dynamics design and time delay estimation (TDE)-based control structure from previous work for three-dimensional trajectory tracking of a thrust vectoring system (TVS)-based torpedo-type autonomous underwater vehicle (AUV) and evaluates its tracking performance through sea trials. The structure of error dynamics design with time delay estimation (EDD-TDE), which incorporates the time derivatives of the position tracking errors, is retained, while the control outputs are formulated as propulsor rotational speed and TVS deflection angle commands with estimation filtering and actuator command limits. Performance is compared with coupled error dynamics with time delay estimation (CDTDE) for two multi-waypoint reference trajectories comprising straight segments, turns, and depth transitions. Numerical simulations apply forces and moments directly to a REMUS-based motion model, while the performance of the actual TVS-based implementation is evaluated through sea trials. Over the post-transient underwater operating intervals, EDD-TDE reduced the 3D position RMSE by approximately 13.7% and 23.4% relative to CDTDE for the two trajectories, respectively, and reduced the vertical RMSE by approximately 78.2% and 76.3%. The surge velocity and heading RMSE values also decreased; however, the along-track position RMSE increased, with a residual offset remaining. These results demonstrate the applicability of the control method to a TVS-based AUV and its improvement in underwater position tracking performance, while highlighting the need for further improvement in along-track tracking performance.