Unmanned Systems Technology 003 | UAV Solutions Talon 120 | Cable harnesses | Austro Engine AE50R and AE300 | Autonomous mining | AUVSI 2015 show report | Transponders | Space systems

39 Cable harnesses | Focus lines, so two connectors would be enough for a mix of power and signals. In what might seem a contradiction, the aim of the connector maker is to get the connections down to a single connector. This provides the simplest, lightest and most reliable implementation, but that can come at a higher cost. If you have one connector instead of three then you can connect it in half a second rather than three – for some systems that makes a difference for the maintenance. So it may be that the harness costs more with rugged sealed connectors, but over the lifetime of the project it removes the hidden cost of connectors that break or need repairing. Smaller connectors are harder to build into a harness though, as you have to pick the right cable to match the connector. You can have a small connector but if the cable isn’t jacketed well enough or shielded then you can get electrical interference, and you have to test the two together to make sure you get the speed you want. However, the growing use of HD video in unmanned systems is placing greater demands on the connector. A camera using an HDMI interface uses 19 pins, which essentially dictates a 24-pin connector. Whether to use fibre optic connections tends to depend on the amount of data being moved and the distance you want to send it, which is not directly relevant to unmanned systems design. In the broadcast industry though, new cameras with HDMI interfaces and even 4K Ultra HD are leading customers to ask about fibre links. These also tend to need connectors that are sealed to the IP68 standard to keep them clean. The changing topology of unmanned systems is also generating more interest in fibre connections. Some connector makers are finding that customers are providing power locally using a battery or solar panels, so they want to run signals over longer distances without the power lines. In addition, connector makers are looking at manufacturing and designing ‘smart’ harnesses that include active components such as diodes, and this is naturally leading to more interest in flexible substrates that can more easily incorporate such devices. Demand here is coming from customers looking at increasing functionality and cutting costs while maintaining reliability. Part of this comes from the introduction of new and smaller connectors. The manufacturers maintain they have an advantage as they handle these connectors every day, whereas a third- party harness maker may not have the same experience. Many customers are building small numbers of harnesses right now but they all have ambitions for high manufacturing rates to enable them to take advantage of discounts from their suppliers. Space and cryogenic applications tend to use micro-D and nano-D connectors, and while they can be expensive they are very small, lightweight and reliable but low-volume items. Conclusion Because there isn’t a mature industry in unmanned systems there’s a lot of room for innovation in harness design and connectors. These are no longer a connectivity afterthought but increasingly an integral part of the design process. Including the connectivity of the system as part of the high-level design allows the interconnect to be optimised and the weight and power requirements to be reduced. New materials and design tools can also be used to cut costs and increase the performance and range of unmanned systems. Acknowledgements The author would like to thank Philip Johnson at Trackwise, John Hopkinson at Tekdata, Lisa Gardner at Fischer Connectors, Dax Ward at St Cross Electronics and Nick Smith at Mentor Graphics for their input into this article. Unmanned Systems Technology | Summer 2015 The connector and harness are a key component in an autonomous system (Courtesy of St Cross Electronics) If you have one connector instead of three then you can connect it in half a second rather than three – that makes a difference for some systems