Adaptive fixed-time disturbance observer-based anti-saturation distributed sliding mode formation tracking control for multi-underactuated AUVs under lumped disturbances

Abstract

During trajectory tracking missions, formations of multi-underactuated autonomous underwater vehicles (AUVs) encounter substantial challenges from lumped disturbances—including unknown environmental effects and model parameter uncertainties—as well as actuator input saturation. To address these issues, this paper proposes a distributed anti-saturation integral sliding mode formation control strategy. The proposed framework incorporates an adaptive fixed-time disturbance observer (AFDO) that employs adaptive parameters to compensate for lumped disturbances, ensuring system stability and reliable performance. To prevent actuator saturation, a novel fixed-time dynamic auxiliary system is introduced to limit actuator inputs within permissible bounds. Additionally, a distributed anti-saturation sliding mode controller using a fixed-time integral sliding mode surface is designed to achieve rapid and stable formation control independent of the initial system state. This approach mitigates saturation effects and ensures a prompt system response. Numerical simulations confirm the effectiveness and reliability of the proposed control strategy.