Connecting UAVs

Louise Davis

Bob Stanton discusses interconnection systems for evolving defence UAVs 

Defence-focused unmanned aerial vehicle (UAV) systems range from larger aircraft formats (such as the Predator) designed to provide long-range autonomous surveillance missions, to very modern designs used as the soldier-borne hand-launched drones seen in the battlefield. Drone and UAV flight style designs also vary widely and include a range of vertical lift signal wing helicopter styles, to multiple rotor vertical lift drones and on to fixed wing and propeller-driven horizontal-flight aircraft. New sensor and detector electronics are being introduced to support these defence vehicles and are greatly expanding the operational capabilities of new drones and UAVs.

Early applications began with greatly improved surveillance cameras and lidar position reporting systems and mobile communications to and from command bases. As data storage capabilities increased, online data compression, rapid transmission and even decision analysis software were uploaded to long-range unmanned aircraft system (UAS) centres. Tactical operations were coordinated centrally via satellite links. Newer fully automated UAVs could operate alone or may rely on remote operators when needed. Those not using any human interaction are often called autonomous vehicles.  

Drone designers can now select and include onboard equipment and payloads based upon the area their aircraft is being used, the application its used for and the regional nation’s regulations (for instance, Europe and the USA have separate rules and regulations for drone usage, as well as the equipment that can be mounted onboard.)    

UAV application-specific cable and connectors

Electrical wiring and connector systems have evolved to assure optimum

reliability and signal integrity required for the many varieties of military based UAVs and drones. New electronic sensors, detectors and actuators are being developed using higher performance complementary metal-oxide semiconductor (CMOS), Gallium Nitride (GaN) semiconductors and even microelectromechanical systems (MEMS). These modern chip technologies operate on lower voltages, require less current and operate at significantly higher signal speeds than older diffusion chip technologies. More image data can be processed, flight control actuators, position tracking and reporting is done rapidly. In turn, UAV and drone flight times can be longer as less energy is consumed during operation.  

Simultaneously, signal and power interconnection systems can use smaller diameter wires and connectors. Cable interconnection ruggedness and high reliability considerations are key in these aircraft. Designers can begin by referencing previous design test data and existing military specifications used in previous battlefield devices. Designers also depend upon working with connector and cable manufacturers with extensive experience in military electronics. 

UAV mission and sensor systems abound as key autonomous developers, such as Leonardo, have focused heavily on expanding technical sustainability and capability. Leonardo is well respected in Europe and the USA for developing complete control platforms, sensors and bi-optional controls on tactical ISTAR missions. Obviously, control, operational management and sensors vary significantly with various forms of unmanned systems from helicopters, and fixed wing UAVs to drones. Longer range LIDAR systems differ from drone cameras as much as the electronics used in various weapon launch and control applications.

Signal and power within each system varies as well. Interconnecting cable and connector styles are available in standard designs. A great option to consider is the rapid customisation of proven standards as UAV electronic system formats and designs change from type and the application they will be used. New UAVs will undoubtedly have some specific needs that may not apply to other formats. Mixed signal types can be built into connectors to offer combinations of power, and signals while reducing size and weight. Quick disconnect latching is also available for specific applications.

 The previously mentioned Predator aircraft often used military-specification circular connectors such as Mil. Spec. 38999, a higher current circular connector for connecting cable from module to box designs. As size and space got tighter in smaller UAVs, the Mil. Specification 83513 Micro-D sized connector offered highly rugged performance in a metal shell that easily withstood shock and continuous vibrations during use. The Micro-D offered a proven standard shell with up to 3A per line at .050in (1.27mm) spacing. More recently, is the growing use of the Mil. Specification 32139 Nano-D connector. This nanosized metal device provided up to 1A per pin on .025in centres, (0.635mm), and because of design, low weight and size. Nano-D connectors have been tested and used in high shock (above 10,000G) conditions, such as when fired from military ballistic devices such as THAAD missile interceptor systems. Their extreme temperature ranges are also similar to Micro-D connectors, and they easily pass operating temperatures of -55°C to 200°C.

Aside from the size and weight challenges mentioned above, there are countless other factors at play today. With cameras, weaponry, GPS modules and other detectors on board many of these light-weight UAVs, there is an increased demand for high-speed connectors. Connectors are responsible for transferring large amounts of high-resolution video and carry with them impedance requirements that were previously a non-issue. In addition, times have changed and these connectors need to help protect from electromagnetic interference (EMI). In addition to solid braid shielding, lightweight metalised braids may solve key issues for insuring the cable to sensors are terminated well at both ends of the system.

For the newest designs, from hand-launched fixed wing to soldier-borne nanodrones, an ideal solution exists. During the design and prototype phase it is prudent to request samples of UAV connectors to insure fit and function. When size, shape, fit and even function needs adjustment, product designers should contract their connector design company and go on-line for a solid modelling session. When the configuration looks good, they should ask for a 3D construction of that new model. It should take less than two days to make a replica of the connector that will fit within the confined spaces of a new UAV module.

Bob Stanton is director of technology at Omnetics