A Guide on Selecting Connectors for UAV Applications

Author : Ryan Smart, VP of Product at Harwin

07 August 2023

The growing use of unmanned aerial vehicles (UAVs) in the security and defence industry is fuelling demand for military-grade hardware. Applications vary from surveying and mapping through to transportation and combat operations.

It is no wonder that researchers at Fortune Business Insights are predicting that the market size will more than double by 2030 - going from $14 billion today to surpassing $35 billion at the end of the decade. This is good news for the connector industry, as more connections will be required as UAV sales increase. 

The growth of military UAV use means there will be a need for more sensor systems for surveillance, reconnaissance, and the like. The more advanced UAVs come fully equipped with sophisticated propulsion and flight management systems, as well as various payloads. On top of this, there is a massive transition to electrification, which is also driving the need to connect these systems. As UAV makers learn new ways to offer upgraded capabilities, connectors that prove easy-to-use in the field will become essential.

Sizing down - powering up
Major adjustments must be made at the component level since reductions in size, weight and power (SWaP) are now a crucial aspect of military design at the system level. Of paramount importance is the ability to guarantee the transfer of acquired data, such as imaging content, across these various systems. Power also needs to be carried throughout system implementations. Both situations call for the specification of military-grade connectors, which offer strong performance characteristics plus extended operational durability. They must be capable of carrying out numerous mating cycles and be deployable in harsh conditions - so resilience to shock and vibration are also important.

Compact, lightweight connectors are currently in demand due to these SWaP dynamics. At the same time, the power and data rates that must be handled are increasing. In addition, the amount of cabling that comes with these components is increasing steadily, which raises possible EMI concerns in the system design.

Figure 1: Combining power and data, Harwin’s MixTek connectors have the compact, lightweight and high-density attributes needed in UAV designs
Figure 1: Combining power and data, Harwin’s MixTek connectors have the compact, lightweight and high-density attributes needed in UAV designs

The stringent requirements now being imposed by UAV applications must be met by the high-reliability, multi-functional connectors. Harwin's Datamate and Gecko systems, widely used in land sea, air and even new space, rely on a unique multiple-finger contact configuration that keeps electrical connectivity intact even when exposed to intense shock or vibration forces.

High reliability connections
Although Datamate connectors are not typically operated in the field in most UAV applications, maintenance and battery replacement/recharge is the exception. In these cases, UAV makers choose connectors that are fitted with guide pins to prevent misalignment, which can result in damage to the pins and potentially cause issues with the functionality of the system. Guide pins are often used when assembling the airframe to assist with UAV build. This is often part of a larger system for guiding and securing the wings and other sub-assemblies (inside and outside the aircraft). The family is capable of delivering mixed technology options that can handle up to 40A of current on each power contact. Using Beryllium Copper for the contacts enables an extended temperature range, covering -55°C to +125°C.
The slim-line 1.25mm pitch Gecko connector family accommodates a far larger number of contacts than competing connector components of equivalent (or even greater) dimensions - thereby presenting engineers with substantial space savings. Their glass-filled plastic housings make them extremely lightweight, which conserves fuel or prolongs battery range. They are able to cope with exposure to extreme temperature levels, spanning from -65°C to +150°C. 

Mating options
When separating and re-connecting modular systems in the field, screw-lok or jackscrew versions are proving popular in the UAV sector, as they can cope with elevated levels of vibration. Screw-loks allow these connectors to be mated and then secured after the fact. Jackscrews, on the other hand, need to be jacked together - which is good for high-pin counts where stacking mating forces can result in tens of Newtons being required to fully mate.

If fast mating and un-mating in the field is a key requirement, the 101Lok fixing hardware (which is unique to Harwin) should be considered. The 101-degree turn bayonet-type mechanism with coiled spring tensioning helps to mitigate vibrational forces, which is great for challenging UAV application environments. An additional benefit is that it does not require the use of a special un-mating tool - a standard one will suffice. Latches are best avoided in these cases as they suit ‘fit-and-forget’ applications. They require specialised tooling for proper use and are typically rated to a far lower number of mating and un-mating operations.

Cable assembly
Harwin has EN 9100 accreditation, which means that it complies with the highest quality standards stipulated by all branches of the aviation sector - for both military and civilian aircraft. Thanks to the cable assembly service that the company also offers, military contractors can outsource this difficult element of the production process (which requires substantial expertise) without needing any non-recurring engineering (NRE) outlay on tooling or having to commit to orders above a certain threshold of units. They can thus have prototypes produced and then finalise the design concept before moving to full-scale production.
Rugged connection solutions that support the previously mentioned SWaP features will need to be found as military aerial technology advances. They should additionally come from a reliable supply chain with zero chance of delays. Furthermore, these connectors must be reasonably priced without sacrificing performance. 

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