Depth control for an over-actuated, hover-capable autonomous underwater vehicle with experimental verification

A PI-D based control system is developed for over-actuated, hover-capable AUVs which enables a smooth transition from hover-style to flight-style operation with system stability and convergence proven using a Lyapunov approach. The performance of the controller is demonstrated by simulation and is verified through experiments. The approach is able to operate over a range of vehicle ballasting configurations, and to imposed external disturbances. The proposed system is computationally inexpensive and does not require a detailed hydrodynamic model to implement. By monitoring the energy consumption on board, the cost of maintaining depth at a range of forward speeds with different buoyancy conditions can be quantified, and their impact on the cost of transport is highlighted for future optimisation of energy consumption. (C) 2016 Elsevier Ltd. All rights reserved.