Adaptive Fault-Tolerant Thrust Allocation for Underwater Vehicles With Resource Constraints

Thruster allocation is critical for the reliable operation of underwater vehicles, particularly under actuator degradation, power limitations, and thermal stress. Existing methods, such as pseudo-inverse or standard quadratic programming (QP)-based approaches, mainly minimize allocation error or energy consumption but often overlook real-time degradation and resource constraints. In this paper, we propose an adaptive fault-tolerant thrust allocation framework integrated with a PID plus Sliding Mode Control (PID+SMC) law for robust trajectory tracking. The approach leverages convex optimization to simultaneously enforce: 1) residual-driven health adaptation that down-weights degraded thrusters online; 2) power-aware allocation ensuring operation within a global energy budget; and 3) thermal-aware constraints that actively prevent overheating. A lightweight residual filter continuously updates thruster health indices, enabling rapid reallocation under faults and efficiency loss. Simulation results across nominal, power-limited, thermal-limited, faulted, and combined scenarios show that the proposed method reduces trajectory tracking error by up to 4.3% and completely eliminates power and thermal violations compared to conventional baselines. This unified framework establishes a foundation for real-time, safety-aware thruster management in marine robotics.