Terminal Phase Navigation for AUV Docking: An Innovative Electromagnetic Approach

This study introduces a groundbreaking approach for real-time 3D localization, specifically focusing on achieving seamless and precise localization during an AUV's terminal guidance phase as it approaches an omnidirectional docking component in an automated Launch and Recovery System (LARS). Through the use of the AUV's magnetometer, an economical electromagnetic beacon embedded in the docking station, and an advanced signal processing algorithm, this novel approach ensures the accurate localization of the docking component in three dimensions without the need for direct line-of-sight contact. The method's real-time capabilities were rigorously evaluated via simulations, prototype experiments in a controlled lab setting, and extensive full-scale pool experiments. These assessments consistently demonstrated an exceptional average positioning accuracy of under 3 cm., marking a significant advancement in AUV guidance systems

The role of lubricant feeding conditions on the performance improvement and friction reduction of journal bearings

Most conventional hydrodynamic journal bearing performance tools can not suitably assess the effect of lubricant feeding conditions on bearing performance, even though these conditions are known to affect important performance parameters such as eccentricity and powerloss. A thermohydrodynamic analysis suitable to deal with realistic feeding conditions has been proposed. Special attention was given to the treatment of phenomena taking place within grooves and their vicinity,as well as to the ruptured film region. The effec to flubricant feeding pressure and temperature, groove length ratio,width ratio and number (single/twin) on bearing performance has been analyzed for a broad range of conditions.It was found that a careful tuning of the feeding conditions may indeed improve bearing performance.FCT - POCTI/EME/39202/200

On the Development of a Mid-Depth Lagrangian Float for Littoral Deployment

This study presents the complete, detailed development process of an enhanced one-man portable Lagrangian float designed for littoral deployment to depths of up to 300 m. The design focused on maximization of the Lagrangian characteristics of the hull, minimization of the noise emission and energy efficiency of the propulsion system, and the versatility of the platform for various scientific missions. The platform is propelled by a variable buoyancy engine that is actuated by an oil-submerged, gas-pressure assisted micro gear pump. The pressure assistance lowers the pressure differential across the pump ports at depth, resulting in quieter and more efficient operation. An enhanced proportional–integral–differential control scheme is employed to pilot the platform. To enhance diving safety, a software safety agent was incorporated. If the software safety agent detects a major failure, a drop weight is released. To eliminate the chance of water ingress through dynamic hull penetration, the drop weight is actuated by an in-house developed magnetic coupling mechanism. An onboard installed hydrophone continuously records and monitors ambient sounds for phenomena of interest and enables commands and mission updates from the surface. For surface recovery, the platform is equipped with GPS and an Iridium beacon for long-range localization, and an RF beacon and strobe for short-range localization and as a backup. The performance of the platform is demonstrated in a simulation and in an actual real sea mission conducted in the eastern Mediterranean at a depth of 10 and 12 m