Development and Experience of a Practical, Pressure-Tolerant, Lithium Battery for Underwater Use
For a number of years, lithium-ion batteries have promised energy and power densities that make them an attractive alternative to the silver-zinc batteries historically used in underwater vehicles. For AUV (Autonomous Underwater Vehicle) application, polymer-electrolyte cells offer the promise of pressure tolerance; this key attribute impacts vehicle design and operational logistics in a number of ways. Primarily, it facilitates the design of arbitrarily large battery packs by obviating many of the problems associated with large, heavy and expensive pressure vessels that would have been otherwise required to house batteries at depth. This allows a single AUV operator to recover the vehicle and remove and replace the batteries in minutes without the down time associated with servicing o-rings and seals. In a military context, this new operational paradigm has made back to back search and classify missions a practical reality. As with all new technologies there is a hiatus between availability, practical implementation and adoption. Many fundamental, logistical and practical engineering problems in design and manufacture have been solved in the past 5 years leading to a range of commercially available batteries with power densities exceeding 100Wh per neutrally buoyant Kg. This paper will explore these challenges, examining specific solutions derived from experience gained through the pressure testing of over 20,000 cells
Autosub6000: A Deep Diving Long Range AUV
With an ultimate range up to 1000 km, a maximum operating depth of 6000 m, and a generous payload capacity, Autosub6000 is well placed to become one of the world’s most capable deep diving Autonomous Underwater Vehicles (AUVs). Recently, Autosub6000 successfully completed its first deep water engineering trials, and in September 2008, fitted with a multibeam sonar, will carry out its first science missions. This paper will describe how we are tackling the design issues that specifically affect a deep diving AUV which must be capable of operating with true autonomy, independently of the mother ship, namely: carrying adequate energy for long endurance and range, coping with varying buoyancy, and maintaining accurate navigation throughout missions lasting up to several days. Results from the recent engineering trails are presented, and future missions and development plans are discussed.
Frequency selective surface design for blinds applications
In this paper, the reconfigurable blind structure with frequency selective surfaces(FSS) for the building applications are presented. Frequency transmission characteristics for different angles of the proposed blind-FSSs are investigated and verified through simulation and measurement. The simulation results show that we can implement the reconfigurable blind-FSS for multiband wireless applications. To verify the proposed paper, two kinds of blind-FSSs, crossed dipole FSS and circular ring FSS are fabricated and measurements are performed for different angles. The proposed structure in this paper which is very simple, can be easily applied to any planar surface for wireless security applications at low cost.