This work is focusing on a buoyancy system in anautonomous underwater vehicle, and the purpose is topresent a theoretical proposal on how the system indetail and in general can be changed to improve theaccessibility to its internal components and to make itmore robust. The largest part in this work is to simplify thehydraulic system, not only to make it more accessiblebut also to mitigate the risk of leakage due todifficulty of handling pipes and couplings. To reacha solution, interviews as well as litterature studieshas been made to identify specific problems. Thecollected data has then been discussed in order tocombine each specific solution to a final construction.The construction is presented with motivation, calculationsand 3Dmodels. The logical thoughts behind the finalconstruction are also presented for easy understanding ofthe choices being made. The design proposal differs from the earlier, two of themajor changes are that the old single direction the pump isreplaced with a new dual directional pump, and the valvemanifold is replaced with a single valve. In addition, allcomponents are now mounted in a chassis that can be easilylifted out from the hull, making the mounting and servicework on the system easier

<p>This master thesis work was done at Saab Underwater Systems AB, a company at the cutting edge of underwater technology. Here torpedoes and other underwater vehicles are developed and manufactured. The major customers are navies of different countries, mostly the Swedish navy. </p><p>The aim of this master thesis is to develop, construct and evaluate an automatic Trim System for Unmanned Underwater Vehicles. The task of the system is to change the position of the centre of mass and the vehicle’s total mass or volume. A system like this gives more opportunities like improved low speed properties, manoeuvre ability and energy consumption. </p><p>Different ways to make this change of total mass and position of centre of mass has been discussed and a choice has been done. A system of chosen concept has then been developed, constructed and evaluated. A part of big importance in this report is the work with simulations to predict the performance of the system and its behaviour. Other big parts has been to find suiting components and to develop the control electronics of the system.</p>

This master thesis work was done at Saab Underwater Systems AB, a company at the cutting edge of underwater technology. Here torpedoes and other underwater vehicles are developed and manufactured. The major customers are navies of different countries, mostly the Swedish navy. The aim of this master thesis is to develop, construct and evaluate an automatic Trim System for Unmanned Underwater Vehicles. The task of the system is to change the position of the centre of mass and the vehicle’s total mass or volume. A system like this gives more opportunities like improved low speed properties, manoeuvre ability and energy consumption. Different ways to make this change of total mass and position of centre of mass has been discussed and a choice has been done. A system of chosen concept has then been developed, constructed and evaluated. A part of big importance in this report is the work with simulations to predict the performance of the system and its behaviour. Other big parts has been to find suiting components and to develop the control electronics of the system.