The US Army’s initiatives for dismounted soldier systems are using real time digital communication technologies to network ground soldiers to a wealth of battlefield and data from smart devices to provide vital situational awareness. Matt McAlonis, senior manager of product development engineering for TE Connectivity’s Global Aerospace, Defense, and Marine business unit, looks at how portable electronic gear requires new connectors and cables that can withstand combat, yet breakaway quickly if soldiers have to bugout.
Today’s ground soldiers can take advantage of advanced digital communication technologies that only a few years ago seemed to be equipment used by imaginary characters like Dick Tracy and James Bond. Smartphones, smart glasses, and smart devices with Internet of Things (IoT) connectivity are rapidly being adapted from the consumer world to the battlefield. Always-on messaging, geolocation mapping, and augmented reality have been re-engineered into dismounted soldier systems that provide a level of situational awareness (SA) unachievable with walkie-talkie radios of yesteryear.
But to achieve this level of functionality, dismounted soldier systems must employ connectivity and harnessing components that are far more robust than commercially available USB connectors and cables used with conventional devices.
The NW end-user device (EUD) is comprised of a specially adapted smart phone that shows graphics on a digital map to give squad leaders on the ground a picture of fast-moving combat information. Data to and from the EUD is relayed via USB protocol over an interface cable assembly (ICA) connected to a tactical radio used for data transmission over secure channels. Environmental and biometric sensors can be integrated into the system to supply vital insight on terrain safety and soldier health.
Critical to the overall performance of dismounted soldier systems is a robust, reliable electrical interconnect system. The EUD and ICA must be seamlessly integrated into the soldier’s vest, pose no serious safety risks, and remain functional throughout the mission’s demands.
A June 2012 white paper on interconnect architecture for soldier systems noted that developing ‘connectors and cables were a continuing challenge, especially in meeting the human factors requirements for size, flexibility, robustness and ability to integrate within the body armor. In addition, the battlefield conditions – sand, dirt, mud, water, and vibration proved problematic with certain connectors.’
Seemingly contradictory requirements were being imposed. On the one hand, a robust, reliable interconnect system was needed. On the other hand, the connectors had to quickly detach in situations where the soldier is either in pursuit or being pursued–or in emergency situations where gear must be rapidly removed to effect escape.
Taken together, these requirements impose performance expectations that commercial off the shelf (COTS) connectors may not be able to meet without substantial re-engineering.
The High Speed USB 2.0 bus uses a twisted pair of wires supporting half-duplex data communication with a data transfer rate up to 480MB per second (Mbit/s) -sufficient for today’s NW soldier systems.
A major challenge, however, is the physical performance of the connectors. Used on many commercial smart phones, micro USB connectors have the advantage of being very compact. They are designed to withstand thousands of connect-disconnect cycles, yet for many smart phone and tablet users, the connector plug, jack and cable transition areas are notorious for breaking at the most inconvenient times.
The RFI requested new connector designs to be developed and tested in accordance with MIL-STD-810G methods that imitate the battlefield environment. During the connector development process, test protocols subjected connectors to a 2,000 cycle mate-de-mate requirement with no loss of signal integrity. A separate procedure included a break-away force test that ensured that the connectors de-mated at a specified value of 15 +/- 3 pounds of tension force.
Electrical performance requirements were also boosted beyond USB 2.0 specifications. An Insulation Resistance (IR) value of 100 megaohms at 500V direct current (DC) was required, along with 5A power rating per contact without compromising signal integrity.
To meet these rigorous MIL-STD-810G mechanical and electrical performance requirements, TE Connectivity (TE) developed the O.C.H. micro circular connector family. O.C.H. connectors are authorized by the US Army for use in Nett Warrior soldier systems and peripheral devices.
The O.C.H. shell is constructed of lightweight aluminum that resists crushing that can otherwise damage flat micro USB connectors. Thermoplastic inserts also minimize weight to keep total connector mass at two grams or less while enabling a small, rugged package well suited for a soldier’s vest. Contacts are copper alloy with plated gold over nickel to minimize corrosion.
Easy mate-demate of O.C.H plugs and receptacles is enabled by simple push-pull coupling without the need for coupling tools such as torque wrenches. And for safety’s sake, the disconnect design enables a fast breakaway.
The fast breakaway feature involved extensive engineering development to determine the optimum design. In the final product, the mating features of O.C.H. plug connector geometries allow a 13-pound breakaway force to pop the plug out of the jack if rapidly jettisoning equipment is necessary.
O.C.H. micro circular connectors are applied in soldier vest cables, batteries, radios, and antennas. However, to create an integrated system, the performance of components in the Interface Cable Assembly (ICA)–which consists of a device interface cable and an extension cable–is critical.
* Heat-shrink tubing, sleeving and overmold components provide insulation and stress relief for cabling. Specially formulated Raychem cross-linked polymeric materials from TE impart useful sealing and electrical properties during the heat-shrink process. The sealing function enables the ICA to remain functional in driving rain and when exposed to mud and sand. The advanced polymeric materials also provide a combination of flexibility and resistance to abrasion and chemicals that conventional sleeving materials cannot offer.
* High-speed copper cable is available that is compatible with matched-impedance contacts and connectors. An integrated connector/cabling combination provides a total solution for achieving optimum performance and maintaining signal integrity while improving electromagnetic interference protection.
However, those portable electronics require electrical interconnect systems as robust, versatile, and responsive as the soldiers who rely on them. As a MIL-STD-810G approved re-engineering of the micro USB connector, O.C.H. micro circular connectors combine rugged construction, lightweight shells, push-pull coupling, quick-disconnect feature, and USB 2.0 bus support. Related developments include flexible and chemical- and abrasion-resistant cable jackets and overmold strain reliefs. High-speed copper cabling is also available that maintains high-speed protocols and withstands harsh environments.
As dismounted soldier systems utilize the capabilities of ruggedized, lightweight, yet responsive interconnect technologies, other innovative smart devices and services can be developed. For example, flip-down smart glass displays with augmented reality can give accurate cues for fire metrics. Or biometric sensors can detect how dehydration or exposure to concussive forces is affecting soldier health. Advanced connectivity technologies can handle these and other challenging applications to deliver state-of-the-art portable electronics that support the mission of ground combat units in the future.