Multi-input Submarine Control Via ℒ1 Adaptive Feedback Despite Uncertainties

The development of a novel adaptive autopilot for the dive-plane control of multi-input multi-output submarines with unmodeled dynamics, based on the ℒ1 adaptive control theory, is the subject of this article. An ℒ1 adaptive autopilot is designed for the trajectory control of the depth and pitch angle using bow and stern hydroplanes. Interestingly, the structure of the adaptive controller remains fixed, regardless of the nonlinearities and external disturbance inputs, retained in the model of the submarine. Unlike the traditional adaptive control laws, the ℒ1 adaptive control input is generated by filtering the estimated control signal. A nice feature of the control law is that it is possible to achieve fast adaptation and desirable performance bounds in the closed-loop system by the choice of large adaptation gains. Simulation results are presented, which show that the autopilot accomplishes precise trajectory control in the dive plane, despite parametric uncertainties, unmodeled nonlinearities, and random disturbance inputs