Wearable Soldier Electronics |
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T
he US military is undergoing a massive transformation driven by the need to develop
new capabilities to conduct military operations in urban areas.
A new doctrine, Military Operations in Urban Terrain (MOUT), identifies the key requirements and capabilities:
The History of Future Soldier Systems An early version of an integrated soldier system appeared in 1989. The US Army Communications Electronics Command (CECOM) developed a prototype of a wearable computer integrated with a helmet-mounted display (HMD) and communications equipment. This system led to the development of the Land Warrior (LW) program "to improve the lethality, mobility, survivability, command and control, and sustainability of infantry soldiers." The first Land Warrior systems in the early 1990's were bulky, heavy and consumed too much power. These systems used microminiature connectors (.050 inch contact spacing) in the backpack electronics packages and nanominiature connectors (.025 inch contact spacing) in the helmet subsystem. These interconnects were costly and extremely fragile. Land Warrior underwent design improvements for next ten years, and will enter full production in 2005. Glenair's Initial Role Glenair manufactures a wide range of interconnect products for tactical battlefield use. These products include man-portable weapons cables, tactical fiber optic cable systems, conduit systems for wire protection on armored vehicles, environmental cables for field training equipment, as well as various ruggedized connectors and connector strain reliefs for shelters, missile and weapons systems. In 1999, Glenair was asked to develop light weight, ruggedized boxes to house batteries and the computer for JEDI, the Joint Expeditionary Digital Information System (Figure 1). The heart of the JEDI system is a ruggedized handheld compute. Other components include a GPS unit, laser rangefinder binoculars and a satphone used for target identification and transmition of the target type and coordinates to a remote joint command center. Circular receptacle connectors, with component parts and packaging modeled after the Micro-D interconnect, were used on the combination battery/junction box. Glenair also furnished the mating plug cordsets. US Army field trials exposed numerous weaknesses in the micro-interconnect design including inadequate environmental sealing and poor cable strain-relief (Figure 2). Glenair proposed a new connector, with improved enviornmental performance and better accomodation for strain-reliefs and other backshell accessories. The new connector (which Glenair had first developed for aerospace instrumentation in 1997) proved to be ideally suited for ruggedized, Land Warrior applications. The Glenair Series 80 connector, also known as the "Mighty Mouse," offered virtually the same package density as the microminiature connector, but added environmental sealing, larger wire sizes, crimp-and-poke contacts, and other features found on traditional Mil Spec circular connectors. A key feature of this connector was compatibility with shielded cable and direct overmolding onto the connector (Figure 4). The original JEDI system evolved into a ruggedized personal digital assistant (R-PDA) computer (Figure 5). This computer is currently deployed in combat. Glenair recognized the potential for this connector in a variety of other battlefield applications, and by 2000, had begun to develop a broad family of these ruggedized, reduced size connectors for dismounted soldier applications. Environmental Performance Requirements Dismounted soldier equipment must be able to function properly when exposed to the harsh conditions of the battlefield, whether in the Arctic, the desert, or in a tropical jungle. Table I summarizes the typical performance requirements encountered in tactical deployment.
Electrical Performance Requirements Early Land Warrior wiring systems were much more complicated than today's version. For example, the original umbilical breakaway cable from the vest to the helmet had thirty coaxial lines requiring sixty contacts. Today's systems utilize commercial serial data protocols such as USB 2.0 and IEEE 1394. These protocols have greatly simplified interconnect wiring. One or two shielded twisted pairs, plus a power line and ground, are sufficient. Today's voltages typically do not exceed 50 volts DC, and current loads are usually under two amps, with battery power lines drawing up to five amps. Early soldier systems had coaxial cable extending from the torso-mounted GPS to a helmet-mounted antenna. Now, GPS units have integral antennas and the helmet umbilical connections no longer require a coaxial connection. Shielding is a primary concern. The US General Accounting Office identified electromagnetic emissions from cables and connectors as one of several major problems on the first Land Warrior systems. The US Army has established a requirement that soldier systems must meet MILSTD-461 radiated and conducted emissions from 2 MHz to 18 GHz. Conventional cable shielding techniques are usually sufficient to meet EMI requirements (Figure 6). Glenair Series 80 connectors have been shown to meet the EMI shielding requirements of tactical computer and communications equipment (Figure 7). Connectors for Dismounted Soldier Equipment A variety of connectors have been used for manportable tactical equipment. Connector types include: M24308 Type D-Subminiature Connectors: The popularity of the D-Sub connector and the low cost led to its use on handheld equipment. The installed cost increases once the connectors are fitted with the necessary shielding accessories. The D-Sub is difficult to seal properly. The drawn steel shells are not strong enough to withstand abuse. Thumbscrews are necessary to mate the connectors. (Figure 8) MIL-C-55116 and “U” Type Audio Connectors: This field-proven family of connectors has typically been used on tactical radios including SINCGARS. The quick-coupling feature and spring-loaded contacts are the two primary advantages of these connectors. However, newer handheld digital tactical radios cannot use this connector because of the size. EMI shielding is also a problem. Breakaway versions are not available (Figure 9). MS Circular Connectors: M26482, D38999 and MIL-DTL-5015 connectors are widely used on tactical equipment. These MS connectors are not suitable for use on wearable equipment because of their size (Figure 10). M83513 Type Micro Connectors have been used on a number of wearable soldier systems including the MILES training gear. The connector size is ideal, but the contact system is prone to damage from sand and dust. The maximum wire size is #24. Attaching shields adds labor and cost. Glenair is reluctant to recommend this connector for battlefield use because of the potential for contact damage caused by debris entrapment. However, when small size is more important than other considerations, the microminiature contact can be successfully incorporated into ruggedized connector packages (Figure 11). Commercial Quick-Disconnect Circular Connectors: Several European manufacturers offer a variety of miniature connectors used on medical and test equipment. Their size, weight and quick release mechanism are appropriate for wearable soldier equipment. However, assembly is time-consuming, and these connectors are not as rugged as required for most battlefield applications (See figure 12). Product Overview: The Series 80 "Mighty Mouse" Connector System The Glenair Mighty Mouse connector is a miniaturized version of a Mil Spec type circular connector. It is approximately half the size and weight of the Mil-DTL-38999 Series III. The Mighty Mouse connector family is designed around a size 23 contact system derived from MIL-C-39029. The socket contact is a split-tine type with a stainless steel hood to prevent contact damage. Contacts are crimped using standard M22520 tools and are snapped into the connector housings. Printed circuit board receptacles are standard. Solder cup versions are also available. The size 23 contact accepts size 22 AWG wire through 30 gage wire. Glenair currently offers 10 contact layouts ranging from three contacts to 85 contacts. The insert assemblies feature beryllium copper retention clips captivated between rigid dielectric insulators. Flourosilicone face seals and rear grommets are bonded to the insulators. The Series 80 family has grown to include five connector styles to suit differing packaging, coupling, ergonomic and performance requirements. These five styles are shown in Figures 13 to 17. All Mighty Mouse connectors are available with a variety of plating finishes, and all types are available with an integral shield attachment and overmolding feature. This feature allows direct attachment of the cable without the need for bulky added-cost backshells (figure 18). The cutaway view on pages 12 and 13 shows the internal construction of the Series 80 connector. MIL-STD-810F Whatever connector type is selected, the equipment must meet the requirements of MIL-STD-810F. This specification covers a broad range of electrical, mechanical and environmental tests for system-level, subsystems and components. This comprehensive specification does not specifically address interconnect performance requirements, but serves as a basis for tailoring interconnect tests as necessary to validate their suitability for soldier systems. New Series 80 Product Developments Glenair continues to expand the Series 80 product line with new insert arrangements. These new layouts include 13 and 26 pin connectors, along with coaxial and power arrangements (Figure 19). Also new for 2005 is the Series 805 triple-start connector. Featuring 1/2 turn to full mate, the Series 805 also features a detent (clicker) mechanism in the plug, along with an EMI spring on the plug barrel (Figure 20). Glenair has also developed a new hybrid "MicroMouse" connector which incorporates Glenair's TwistPin microminiature contact into Series 80 connectors. Glenair currently offers a 55 pin arrangement in a shell size 9 connector (Figure 21). Although the TwistPin can be susceptible to damage from debris contamination, it offers a solution when connector size takes precedence over other considerations. This 55 pin connector is deployed on a tactical imaging system. Right angle header receptacles for printed circuit boards are also available. Note the unique rectangular mounting (Figure 22). Glenair has developed standard overmolds and cable to support rapid prototyping and pre-production of overmolded cordsets. A typical overmold tool is shown in Figure 23. The Series 80 product line expansion has led to a major ongoing program to increase component capacity and assembly capability. Most importantly, Glenair is adding hundreds of Series 80 connectors to Same Day stock. Table II: Wearable Soldier Systems: Interconnect Problems and Series 80 Solutions The table below summarizes the interconnect problems encountered with wearable soldier systems and explains how the Series 80 Connector addresses each issue:
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