Allocation Integrated Sliding Mode Control for Heading Autonomous Underwater Vehicles with Varying Speeds

This paper addresses the challenge of robust heading control for Autonomous Underwater Vehicles (AUVs) operating under variable speed conditions, subject to system nonlinearities, parametric uncertainties, and actuator constraints. We propose a hierarchical control architecture that integrates Sliding Mode Control (SMC) with an optimization-based Control Allocation (CA) scheme. The outer-loop SMC guarantees robustness by computing the required total yaw moment to reject disturbances and track the reference heading. The inner-loop CA then optimally distributes this virtual control effort to individual actuators, explicitly accounting for saturation limits and speed-dependent actuator effectiveness. The performance of the proposed SMC-CA strategy is validated through comprehensive numerical simulations. Results indicate that the system maintains high tracking accuracy and stability across a wide speed range, demonstrating significantly faster transient response and superior disturbance rejection compared to a conventional PID controller in various scenarios, including step changes and abrupt speed variations.