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. A system stability and convergence is proven using a Lyapunov-based approach. The performance of the controller is demonstrated by simulation but crucially is proven to provide satisfactory performance experimentally. 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 cost of transport is highlighted for future optimisation of energy consumption.

A sliding mode heading control system is developed for overactuated, hover‐capable autonomous underwater vehicles (AUVs) operating over a range of forward speeds. A simplified switching function is introduced, and simulation studies are proposed accordingly. The results with this novel switching function show a significant improvement in the chattering problem when compared to other conventional switching function candidates. Studies on sensitivities to a range of hydrodynamic parameter uncertainties are presented, and the parameters that have major influences on the sliding mode control performance are highlighted. The proposed control system is also proven in the field trials to enhance vehicle response, yielding consistent, and robust performance over the entire range of vehicle's speeds, even when subjected to external disturbance. It also shows superior heading tracking performance when compared to a proportional‐derivative (PD) based approach implemented on the same vehicle. However, this improved performance requires intense control actions as a trade‐off, causing the AUV to expend more energy than with the P‐D approach. Path following trials, where the AUV is demanded to follow a set of GPS coordinates at the water surface, are presented. These demonstrate the applicability of the proposed heading control system in a practical operation. The presented SMC scheme can be applied to any vehicle straightforwardly, but the control allocation part may need to be modified regarding the actuator configuration of that vehicle.

Abstract-For an AUV to perform a long-range mission with its maximum endurance, its energy consumption during transit must be kept to a minimum. This paper presents an improved cost function for a grid-based genetic algorithm (GA) path planning in 2D static environments. The proposed function consists of energy consumption terms that are estimated according to dynamics of a hover-capable AUV -notably Delphin2 AUV. It seeks for a path that requires least effort for the vehicle to move along. A simulation was written in Matlab and the outcomes of the GA with the improved cost function are compared with the ones of a GA with an optimal distance approach as well as an A* approach. It is found that outcomes of an improved cost function require less energy compared with the other techniques.

This paper provides a review on development of unmanned surface vehicles (USVs). Their potential applications and development trends are also discussed. Based on active works in this fields, USVs may potentially be integrated into existing force structures of manned ships, offering a cost-effective solution for performing various types of marine operations with a minimum risk on the personnel.