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

38 Focus | Cable harnesses for installation in component-crowded vehicle bodies, and is notably falling in price faster than many other jacket options thanks to wider demand driving increased supply. Conductors When it comes to conductor wires, many options are available, but industry trends continue to show strong preference for just a few of them. Inside the insulation layer, there is either a single solid core of wire or multiple twisted strands. Solid cores are simple and inexpensive to manufacture, although crimping them to a connector can be challenging, as is routing them among electronics and engine components owing to their poor flexibility. Multi-strand designs such as twisted pairs or litz wires are becoming more popular than solid-wire types. This is partly down to their flexibility, but they are also ideal for vehicles that integrate a lot of complex electronics, as they reduce AC power losses in high- frequency designs. Being able to carry many different kinds of signals and voltages within one jacket is advantageous for sophisticated SoC boards that carry different processors and power transistors. Also, a high quality of twist or stranding ensures lower EM emissions from each wire, between pairs of wires and from external sources, greatly aiding data fidelity. Such quality is paramount for self- driving road vehicles and first-responder aircraft, which must constantly handle enormous (and fast-growing) quantities of information and analytics. Several options for conductor material are available, with copper remaining the chosen material for at least 95% of cabling. It has the best balance of cost, conductivity and resistance to heat and corrosion. Silver offers higher conductivity than copper per volume, but is far less cost- effective. A given copper wire can match the conductivity of an equivalent size of silver wire by making it just 5% thicker. Furthermore, silver is prone to oxidising and losing conductivity. Gold is also highly conductive but it’s expensive. Gold and silver are therefore generally limited to contact plating. Aluminium is finding use across vehicles, engines and electronics thanks to its lower cost and higher conductivity- to-weight ratio than copper. This is an important metric for UAVs. However, copper remains superior in terms of power-to-volume ratio, and aluminium is more prone to corrosion and temperature-related expansion and contraction, so it needs more maintenance, which can offset the cost advantages in the long run. Shielding As unmanned vehicles pack more electronics, RF transmissions and propeller drives onboard, the issue of transmitted ‘noise’ becomes an imminent concern for their ability to function. Greater hybridisation, and electrification in particular, will present a major risk here, owing to electric motors and motor/ generators relying on PWM connections. As ever-higher voltages emit EM radiation that could cause wires carrying PWM signals to act as antennas, this could propagate such noise throughout an entire vehicle. Cable harnesses have the advantage of being able to integrate protection against EMI in the form of shielding, typically either aluminium foil wrapping or braids between the inner insulation layer and outer insulation jacket. Naturally, a full wrap provides the highest level of protection but it costs and weighs more than a braid, and provides an unnecessary degree of shielding in many cases. Battery cables for example might need significant temperature and fluid protection, but they are often at far less risk of EMI than many other harnesses in a vehicle. Newer designs use shielding in different ways. With new kinds of harnesses that pack several different kinds of wiring, covering individual wires and pairs of wires can be highly useful for mitigating crosstalk between different ‘regions’ inside cable jackets. Much like increased insulation though, adding shielding reduces cable flexibility, and increases weight and expense. Unmanned vehicle manufacturers therefore need to map out the areas where shielding is needed most, and where it could be spared. Connector considerations Some of the most tangible technical advances relating to cable harnesses are occurring more on the connector side. For example, while gold and silver are often used as highly effective contact materials in many applications, they June/July 2020 | Unmanned Systems Technology Shielding is becoming evermore critical for autonomous vehicle cables to guard against EMI from onboard sensors and electronics (Courtesy of Omnetics)