Unmanned Systems Technology 016 | Hydromea Vertex AUV | Power management systems | Unmanned Space Vehicles | Continental CD-155 turbodiesel | Swift 020 UAV | ECUs | DSEI 2017 Show report

32 P ower management strategies vary according to the type of power source, whether it is batteries and their different chemistries, or fuel cells or solar cells. Different chemistries discharge in different ways, generating different amounts of energy and heat. All this needs careful management, which has an impact on almost every part of the system’s design. The strategies also differ between the platforms and how they are charged, whether that is via an onboard system or an external charger. In addition, the growing use of autonomous vehicles is driving developments in wireless charging architectures to reduce the need for operators to repeatedly fit fresh batteries. Lithium-ion and lithium-ion polymer cells are the current chemistries of choice in electric cars and UAVs, although nickel metal hydride (NiMH) is being used for electric trucks, and lithium-sulphur and aluminium-air cells are also used in underwater unmanned system designs. The different chemistries were examined in UST issue 4 (Autumn 2015). The cells are combined into a battery, which are in turn combined into a battery pack. The battery management system (BMS) can be applied at the cell, battery or pack level, and increasingly requires a system-wide power management architecture. This is needed to address the growing power requirements of the electronics used for autonomous operation. Traction In an electric car, lithium-ion polymer battery cells are used because of their light weight. However, they have a tight tolerance on the discharge voltage – Nick Flaherty explains how the growth in autonomy is changing the nature of unmanned vehicle power management Taking charge The design of a new chassis for electric vehicles is changing the way the battery packs themselves are designed (Courtesy of Williams Advanced Engineering) October/November 2017 | Unmanned Systems Technology