USE Network launch I UAV Works VALAQ l Cable harnesses l USVs insight l Xponential 2020 update l MARIN AUV l Suter Industries TOA 288 l Vitirover l AI systems l Vtrus ABI

42 Focus | Cable harnesses Manufacturing considerations Given the proliferation of connections throughout unmanned systems, vehicle manufacturers should pay attention to the types of issues that will affect the production processes of cable harnesses. One tiny increase in the cost and complexity associated with a vehicle’s standard cable design could be mirrored across every cable throughout the chassis, resulting in a huge leap in overall expense and hampering both repeated prototype iteration and eventual sales. The same effect also applies to any manufacturing weaknesses, which could mean hundreds of points of potential mechanical failure being distributed throughout the vehicle’s body. Naturally this concern is then further multiplied by the number of vehicles to be manufactured. In addition to CAD software improvements to enable better advance detection of flaws and weaknesses, automation is becoming widespread across cable manufacturing, enabling controls and checks for design and quality parameters across increasingly lengthy lines of machinery. Flexible circuits in particular can be highly automated in their production owing to their reduced dimensions and layer-by- layer construction. The question of whether to crimp or solder cables to their connectors continues to divide opinion. With the key aims of manufacturing being high- quantity outputs with consistent quality, however, crimping is by and large the more popular choice. The simplicity of stripping a wire, inserting it into a terminal and squeezing that terminal with a repeatable degree of force to deform it tightly around the conductor’s strands is the simplest approach to ensuring solid mechanical and electrical connections. The use of manual crimping tools is relatively easy to learn, and the tools are designed to apply a consistent force to terminals and wire jackets. Such is the effectiveness associated with crimping that more and more cable manufacturers are moving from hand- crimp tools to semi-automated machine crimping. Although an expensive investment, such machines can vastly increase the throughput and quality control of finished wiring harnesses compared with manual workers. Soldering, however, takes more time owing to the need to melt the soldering medium and heat the two mating surfaces before joining them together. It also requires considerable focus and attention to detail on the manufacturer’s part to ensure accurate application of the solder material, and to prevent accidental melting or burning of the cable jacket. A skilled worker though could produce soldered connections that surpass even a high-quality crimp. Soldering can therefore be ideal for smaller orders of cables, such as for a customised UAV design with a short production contract with a single company. Using a soldering iron tool could lower the costs of a small order even further, as they cost far less than many crimping tools and machines. And while both options should provide similar lifetimes for a cable harness, soldered connections can produce a more airtight seal against gradual corrosion of copper wire. However, the standardisation of terminals and processes for crimping means it still generally produces less variability in lifespans between harnesses compared with soldered wires. Conclusions While many of the basic principles of cable harness manufacturing and design have remained the same over the past few years, the innovations achieved in the sector have undoubtedly kept pace with the advancing needs of unmanned systems developers, in terms of quality, consistency, and bandwidths for power and data. Acknowledgements The author would like to thank Dax Ward of St Cross Electronics, Giorgio Potenza of Harwin, Philip Johnston of Trackwise, Bob Stanton of Omnetics, and Thierry Pombart, Don Worden and Greg Jones of Ulti-Mate for their help with researching this article. June/July 2020 | Unmanned Systems Technology Trackwise has recently developed a 26 m-long flexible circuit for integration inside and across the wings of a HALE UAV (Courtesy of Trackwise)