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

40 are prone to short-circuiting when doused in water, which could cause problems for USVs, UUVs and maritime UAVs. Many connectors with IP67 and IP68 sealing have been developed to protect electrical connections in maritime vehicles. Also, new developments such as niobium contacts hold great promise for marine harnesses by removing the problem of shorting. Niobium contacts generate a passive film around themselves when simultaneously energised and touching water. The film serves as an insulator, keeping the connection isolated electrically from both the surrounding water and nearby contacts. When two niobium contacts are mated, the film is breached, re-enabling electrical connectivity; when they are unplugged, the film is created once more. This ‘self-healing’ property has been found to work at up to 60 V, covering most UAV, automotive and marine hydrography power requirements. Several other improvements in connector manufacturing are also leading to advances in cable harnesses. More and more connector companies are improving their ability to ‘design to fit’, using the latest CAD software to design nano-D connectors to provide shielded connections to small, machine-braided cable assemblies with custom-machined jackets, ensuring no weak points in environmental or EMI protection. Also, the growing use of such software enables CAD files to be shared between groups and organisations, allowing fast back-and-forth iterations between cable manufacturers and vehicle designers. That means the different parties can have an input into the balance between the differing needs that cable assemblies would otherwise struggle to achieve. The smaller and more complex cable harnesses become, the higher the risk of a shielding gap, speed loss or potential ‘pull-out’ owing to a poor-quality fit between cable and connector. It is increasingly common to test that cables with nano-connectors can withstand 35 lb (16 kg) of pulling force, given the heave, g -forces or other shocks that unmanned vehicles can routinely be subject to. Larger cables of course pose a crowding risk inside the tight spaces within a vehicle chassis; however, new connector designs are emerging that use a two-piece design. These are expected to be able to integrate larger cable bundles into smaller packages, to help alleviate any problems with connectivity congestion inside unmanned vehicles. Flexible circuits Alongside the advances in more conventional cable harnesses, there is growing adoption of flexible circuit harnesses. Although the technology was originally conceived and developed as a replacement for traditional wiring harnesses – and are still available as such – they have evolved to act as entire printed circuit boards in a bendable as well as flat form that could otherwise take up considerable space between vehicle subsystems. Flexible circuits bring a range of potential benefits over conventional cable harnesses. Perhaps the most obvious is their mechanical versatility, which allows them to bend and fold tightly around box-shaped enclosures and engine blocks (except in their planar axis) with a far smaller bending radius than typical cables. This also makes them less prone to wear and tear from metallic structures inside vehicles, as their flexibility means reduced pressure (and therefore friction) against solid surfaces. They can also provide greater electrical performance, as their layer-by-layer builds are easier to control for low inductance and EM emissions than conventional cabling. The flat shape of the conductors also provides better heat dissipation and greater current capacity than round wires of equivalent density. And despite their wide shape, flexible circuits can also offer greater packing density than round cables, with some layers being thinner than 25 μm. That could therefore enable more connections for a given weight allowance, or the same number as the regular harness it replaces but with less weight. Studies indicate a weight reduction of as much as 75% over some traditional harnesses. These power, weight and integration characteristics mean wide applicability across the gamut of unmanned vehicles. For example, flexible circuits can fit into inaccessible spaces between components in autonomous road vehicles while reducing RF congestion inside. They can also reduce the volume and weight taken up by connections in the wings of UAVs. This is critical for developing unmanned HALE June/July 2020 | Unmanned Systems Technology Flexible circuits can fit around sharp corners and through tight spaces with minimal abrasion or tension on the harness (Courtesy of Harwin)