Adaptive LPV-MPC and NFTSM-ESO Cooperative Control Method for Underactuated AUV

This paper addresses depth-heading tracking and roll stabilization of underactuated autonomous undersea vehicles (AUVs) subject to missing sway/roll actuation, rudder-induced channel coupling, actuator constraints, and time-varying marine disturbances. A cooperative control framework integrating adaptive linear parameter-varying model predictive control (LPV-MPC), a nonsingular fast terminal sliding mode extended state observer (NFTSM-ESO), and a roll proportional-derivative(PD) inner loop is proposed. A roll-angle-scheduled depth-roll-heading LPV error model is first established by describing the variation of elevator and rudder effectiveness under roll attitude, so that the influence of roll on the depth and heading channels can be incorporated into the prediction model. An error-disturbance-driven adaptive LPV-MPC is then developed to solve a constrained control-increment sequence under rudder magnitude, rudder-rate, and roll soft constraints, thereby producing feasible rudder-angle commands. The NFTSM-ESO rapidly and smoothly estimates lumped disturbances caused by currents, wave-induced moments, hydrodynamic uncertainty, and unmodeled dynamics; the estimates are used for feedforward compensation and weight scheduling. A roll PD inner loop is superimposed on the rudder channel to provide high-bandwidth roll damping and reduce roll-heading coupling in the outer prediction loop. Simulation and ablation results demonstrate that the proposed method outperforms standard MPC+LESO, fixed-weight LPV-MPC, and the scheme without roll inner-loop compensation in depth error, heading error, roll suppression, and constraint feasibility.