MOTH-An underwater glider design study carried out as part of the HGF alliance ROBEX

Abstract

Underwater gliders have been conceived more than 20 years ago and as they are building up on concepts and technologies that were developed used for ARGO float systems have reached a maturity that give them a specific role in observing programs [Barker]. Why then starting a new design? It is exactly the success of the current glider systems that lead to revisiting the basic design and exploring alternative vehicle concepts. Current glider designs are suffering from limited scientific payload capacity which is a good motivation in its own right. Furthermore employing more energy efficient, low drag designs would vastly extend the application range. With the MOTH design study we were picking up a concept that is now extensively used in unmanned flight vehicles (drones), the blended wing design. Earlier attempts in that direction have proven to be quite successful [Jenkins]. In particular higher horizontal speeds could be reached and with the blended wing shape offering new payload capabilities other sensor types (sonar systems) will be integrated. Making use of pre-existing knowledge and experience the project will be structured along the lines of a systems engineering approach. The scientific rationale is based on the needs of quantifying the particle flux in the upper part of the water column in regions of interest, like the Northwest African margin. Here MARUM has already a long term record of flux studies so that the anticipated glider missions can be validated against this data set. The scientific payload is defined based on this observation scenario which implies small flight angles and higher horizontal speeds (up to 1 kn). The endurance will lies in the range of days to a few weeks so that typical the glider system will be deployed and recovered during a single cruise. A particular emphasis will be given to assessing and enhancing the operational reliability of the system. This includes both the hardware and the software side of the system which implies that well defined testing procedures have to be described. During field tests it is planned to make use of the WAVEGLIDER (Liquid Robotics) that offers unique opportunities to track the trajectory of the glider and to set up a communication link. In this presentation the basic system design will be presented to illustrate on how to make best use of the hull shape by employing new sensor integration concepts. Fabrication aspects together with a first sketch on the control architecture will be addressed as well.

High Accuracy Attitude and Navigation System for an Autonomous Underwater Vehicle (AUV)

“…Generally, the full error model in the previous section is required to assess the performance of inertial navigation systems operating for long periods: for our glider applications, flight times are typically of the order of 2-3 days rather than weeks [35].…”

Preliminary Study for AUV: Longitudinal Stabilization Method Based on Takagi-Sugeno Fuzzy Inference System

“…Our vehicle has the task to explore coastal areas full of obstacles (see Figure 1 b for comparison) [ 20 , 21 , 22 , 23 ] and for longer lasting measurement cruises and its design is accompanied by a specific longitudinal-stability analysis.…”

High Accuracy Buoyancy for Underwater Gliders: The Uncertainty in the Depth Control

“…An underwater glider is a vehicle that, by changing its buoyancy, moves up and down in the ocean like a profiling float [16]. It uses hydrodynamic wings to convert vertical motion into horizontal motion, moving forward with very low power consumption [17,18,19,20,21,22]. While not as fast as conventional AUVs, the glider, using buoyancy-based propulsion, offers increased range and endurance compared to motor-driven vehicles and missions may extend to months and to several thousands of kilometres in range.…”