Dynamics and robust control of underwater vehicles for depth trajectory following

This paper addresses the robust control synthesis of diving/climbing manoeuvres for underwater vehicle in the vertical plane. First, a new state-space representation for the vehicle dynamics is presented, and the corresponding problem formulation is clearly stated. Next, the two-controller set-up using a H-infinity-loop shaping design is employed to deal with the bottom following capability and robustness issues. Then the reduced order control system with a Hankel norm is evaluated in the frequency domain. In addition, the preview control approach is used to improve the overall tracking performance for undersea manoeuvres. The specific control tasks include the tracking of a set of depth profiles or ocean floors. Simulation results show that control objectives are effectively accomplished in spite of model uncertainties. Finally, it is found that the proposed control methodology is suitable for the depth trajectory following applications over a wide range of operating conditions.