Unmanned Systems Technology 024 | Wingcopter 178 l 5G focus l UUVs insight l CES report l Stromkind KAT l Intelligent Energy fuel cell l Earthsense TerraSentia l Connectors focus l Advanced Engineering report

82 Focus | Connectors laser ablation removal of the insulation material around the copper wire, as it avoids any potential nicks or cuts in the copper wire from mechanical strippers. Over-moulding – the injection of polymer materials into a mould to cover a given device – is also available from some connector manufacturers. This is typically used to seal the cable jacket to, or over, the connector assembly, effectively binding it into a single functional connector. As well as creating a more secure connection, over-moulding offers higher volume (and thus less expensive) production of custom designs for connector shells. It can also assist in designs that include a grip in line with the cable, or particular polymers in line with an environmental application. On the other side of the interconnection, various pins and sockets are available. Solid-pin and twist-pin contacts have been used in unmanned systems connections for decades now, and meet or exceed military and aerospace specifications. The fastest-growing type are probably spring-loaded contacts, with several advantages derived from their flexibility relative to solid-pin and twist-pin contacts. These including long life – up to 300,000 mating cycles – as well as improved blind mating (fitting plugs and receptacles without necessarily needing to physically see them) and higher misalignment tolerances. They can also be designed with small profiles and pitch, as low as 1.75 and 1 mm respectively. Their flexibility also means they are suitable for bayonet-latched connectors and other configurations that require the contacts to ‘slide’ or move in an axis perpendicular to the plug or receptacle. That also helps to wipe the spring contacts of particles and contaminants, helping to maintain low resistance over time. Being made (usually) from beryllium copper gives them extra abrasion resistance and strength, and helps prevent wear. Connector manufacturers continue to exploit this flexibility to come up with entirely new design categories for connector systems. One of these is completely un-keyed, and thus configured around a circular connector with a 360 º mating capability. It relies on using spring-loaded pins in the receptacle to be mated from any direction to the concentric circular contacts on the inner face of the plug. Lastly, the ‘give’ that the flexibility of spring-loaded pins provides also makes them more suited to high shock and vibration tolerances than solid pins, which can make them better for vehicle applications in general. Spring contacts have their disadvantages, however. Water, dust and oil can seep into the piston mechanism where the contact head is held, prompting some manufacturers to devise protections against this, such as anthracite-nickel coatings for resistance against salt-mist spray in USVs and maritime UAVs. Sealing the piston sections behind a guard membrane, made from silicone or PEEK plastic, can also provide sufficient protection. There are various locking methods for connectors. Bayonets are fast and relatively easy to mate, as are push-fit connectors, particularly compared with screw connectors. They also need no special tooling, as they are self-securing. However, the degree of security in bayonet and push-fit connections can be far less than in screw terminals. The vibration and shock typical of more powerful UAVs and UGVs can make screw locking essential for ensuring a secure connector, whether it uses a set screw inside the housing or two fasteners in a metal plate on either side of it. That said, screw terminals can February/March 2019 | Unmanned Systems Technology Typical micro-D connectors carry 3 A per wire, for 24 to 32 AWG sizes, and more than 100 contacts and wires can be integrated in a single connector (Courtesy of Nicomatic) The fastest growing type of contacts are spring-loaded, with advantages derived from their flexibility relative to solid-pin and twist-pin contacts