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

October/November 2017 | Unmanned Systems Technology 38 needed to meet the redundancy requirements. The move to 48 V also has an impact on the power management in the rest of the system, particularly with an increased need for electrical isolation. Here the mechanical requirements such as the spacing between the input and output pins are vital, so there are certain power management applications that have lots of input and output (I/O) lines that struggle with isolation, for example a microcontroller talking to an IEEE 485 or CAN data bus. Other, more fixed-function applications such as an isolated CAN bus consist of three chips – a microcontroller, isolation chip and physical (PHY) interface – so putting the PHY and isolation together at 48 V makes sense to reduce space and cost. Smart chargers Often the power management is external, especially in smaller UAV designs, and the chargers used are becoming increasingly smart. Chargers are becoming power managers that provide universal power delivery to any load from a variety of power sources. The power manager implements the power conversion automatically without any intervention by using a set of software algorithms and custom hardware, taking power from other batteries, wall outlets, solar panels or fuel cells. Each of these input sources needs different management, for example using MPPT for the solar panels. Detecting the different sources and outputs can be a challenge, but one approach is to use a smart power cable. This has a data device such as an EEPROM chip embedded in the connector, with an ID number. The ID number is read by the smart charger, which then pulls up the appropriate combination of input control algorithms and output control, for example taking power from a UAV’s back-up fuel cell to charge a lithium-ion battery pack. More manufacturers are adding intelligence and connectivity to chargers. This is allowing an app on a tablet to access detailed data about the use of the charger. The data can range from information such as charging times, temperatures and currents to when the battery pack was connected to and disconnected from a system. This can prove valuable, not only in terms of the state of the pack but also how it is being used. For example, instead of being regularly charged, a pack may be repeatedly inserted and removed from a system, which can affect its lifetime. Smart chargers are now allowing manufacturers to gain access to this data to help with the reliability of the overall system Modular versus custom Power is a complex design issue, and many suppliers try to minimise the complexity of the overall system design with modular blocks that are plug and play. While this can make the development process quicker and easier though, it reduces the opportunity to optimise the power consumption throughout the entire system. This system-wide optimisation provides the best way to squeeze as much power as possible out of modern battery packs. While new technologies such as solid-state lithium-ion packs, which can store more energy and support faster charging, are under development, they are unlikely to be commercially available for the next four or five years, so the challenge of range and flight time remains critical for unmanned system developers However, this challenge can be addressed in a different way, with wireless charging. Wireless charging Wireless charging is a key element in the evolution of electric and autonomous vehicles by allowing the systems to charge themselves when necessary, but the technology behind it is not simple to implement. It enables a vehicle to charge while it With higher voltages in a 48 V system, electrical isolation becomes more important (Courtesy of Silicon Labs)