"Distributed Tube-Based Model Predictive Control for Trajectory Tracking of Unmanned Underwater Vehicles"

"Conventional hierarchical architectures for Unmanned Underwater Vehicles (UUVs) trajectory tracking separate motion control from thrust allocation, which leads to cumulative mapping errors, inefficient constraint handling, and suboptimal performance. Furthermore, centralized nonlinear optimization faces the curse of dimensionality and limited robustness in complex environments. To address these challenges, this paper proposes a Distributed Direct Thruster Speed-Optimized Tube Based Model Predictive Control (Tube-MPC) scheme for UUVs. By directly employing propeller rotational speed (PRS) as the decision variable, this approach bypasses the traditional thrust allocation stage, effectively eliminating mapping deviations. To manage the resulting non-affine input characteristics, an improved Tube-MPC framework is constructed, integrating an actuator-level LQR vector sliding mode auxiliary controller to provide independent robust compensation against disturbances and coupling errors. Additionally, to resolve the real-time constraints of high-dimensional optimization, a distributed architecture decoupling horizontal and vertical dynamics is established, utilizing a non-iterative cooperative strategy for parallel computation. Comparative experiments in indoor and outdoor environments demonstrate that the proposed method significantly enhances tracking accuracy and heading stability while satisfying real-time requirements."