Leveraging the benefits of small form factor boards for military wearable computers
When SWaP REALLY matters: SFF boards in wearable military computers.
As the military demands wearable computers that reduce SWaP without compromising performance, durability, and reliability, engineers must provide innovative design solutions to meet these requirements. This article examines how creative approaches in designing SFF boards and leveraging advances in COTS products can help the military accomplish its battlefield objectives.
The military has a strong directive when it comes to military electronics – reduce SWaP. Size, Weight, and Power (SWaP) is a major driving force behind the development of modern computer equipment destined for the battlefield. In few places is this directive more evident than with wearable computers. With advancements in Small Form Factor (SFF) board-level technology, wearable computers are increasingly being integrated into SWaP-constrained military operations.
For decades, the U.S. Army has envisioned the use of small wearable computers to assist with battlefield tasks and serve as powerful communication devices for the warfighter. Different from traditional mobile, portable, or handheld computers, these wearable computers are used for applications that require computational support while the user’s hands, voice, eyes, or attention are actively engaged with the physical environment. However, wearable computers are only realistic if they are lightweight and ergonomic – soldiers must be able to transport or wear the devices for extended periods of time. If these devices are too heavy or cumbersome, they can be more of a hindrance than an asset.
The average ground soldier carries up to 130 pounds (59 kg) of gear, depending on the mission. As a result, the Department of Defense is seeing an increase in musculoskeletal injuries – sprains, stress fractures, and neck and back pain. In combat situations, the weight of the gear can reduce speed and response times, decrease range of motion, and increase fatigue, all of which could mean the difference between life and death. It is this reason why every extra ounce or gram of weight added to a warfighter’s load needs to be carefully considered.
The main challenge when designing SWaP-optimized wearable computers for the military is finding a balance between size, weight, and power consumption without compromising performance, durability, reliability, and the extensibility of the system. Achieving this balance between high performance and decreased size, while building in some degree of customization for targeted applications all in a rugged package, is a top priority for the military’s wearable computing programs.
SFF advancements boost wearable computing
Long gone are the days when small form factor boards were limited to a few types of standard form factors like the venerable PC/104 or PMC. Today, while strategies vary among the small embedded computing standards groups, there’s definitely been a renaissance of new ideas and innovation in both standard and non-standard small form factor compute modules. Standard SFF boards such as Qseven, Pico-ITX, mini-ITX, StackableUSB, COM Express, MicroETXexpress, along with a variety of small vendor-specific boards, are playing a crucial role in making wearable computers more practical and useable for today’s warfighter. Groups like the PC/104 Consortium, the Small Form Factor Special Interest Group (SFF-SIG), and VITA continue to focus on trying a variety of different approaches to suit the miniaturization of board-level electronics.
For military and other SWaP-constrained applications, next-generation SFF boards have demonstrated significant gains in performance and size over their traditional PC/104 counterparts. For example, the PCIe/104 and PCI/104-Express standards, developed to support up to x16 lane PCI Express for high-speed I/O in a stackable configuration, can deploy the latest processors, such as the multicore Sandy Bridge Core i7, which is well suited for higher-performance applications. By combining the elements of multicore and advanced integrated graphics, the newer generation of processors can improve the speed of applications by up to four times.
Similarly, some small form factor Computer-On-Modules (COMs) can efficiently pack in high-performance functionality while offering tremendous I/O flexibility because mating baseboards are tailored to the preferred type of output connectors for the application. The advanced integrated circuit packaging techniques of small form factor COMs provide for a small physical footprint, high I/O count, integrated thermal management, and reliable surface-mount technology assembly for rugged environments where high reliability is a must. The extensive use of Serial I/O interfaces, such as PCI Express and USB (as compared with legacy parallel interfaces such as PCI and ISA), minimizes the space required on the physical board layout while increasing the bandwidth of data available for core computing and I/O functions.
Purpose-built boards preferable for size optimization
In most wearable applications, however, a purpose-built SFF board is usually the most efficient approach as every ounce and inch must be minimized. Trying to fit a “square board” (an off-the-shelf standards-based board) into a “round hole” (a very specific wearable form factor) may not work. Purpose-built boards can leverage board designs from standards-based or other form factor boards and be tweaked to optimize them for the smallest possible form factor.
Power considerations in wearable systems
One of the most significant trends impacting small form factor boards is the proliferation of boards based on Intel’s Atom processor. The emergence of the Atom means there’s no longer a reason to suffer with high power dissipation as a trade-off for using an Intel Architecture platform. With its exceptionally low power consumption/dissipation (3 W average, 6 W peak), the Atom imposes little to no impact on the user, eliminating many inherent problems with wearable computers. For the military, another critical feature for adopting the Atom is its embedded lifecycle support.
Solutions for battery limitations
Batteries are a critical component to wearable computers as they are the lifeblood for the entire system. However, how batteries are incorporated into a wearable system is usually limited to fixed, integrated batteries or remote/external batteries. Integrated batteries are typically required in wearable SFF applications. While external batteries are also desirable for wearable computers, they require separate cables and additional housing for ruggedization and mounting features, which can easily add three-quarters of a pound just in packaging. Additionally, external batteries can cause reliability issues as they may have to be removed due to interface cabling problems. [Batteries are a sizable portion of a warfigher’s equipment. See sidebar above.]
To mitigate these issues, wearable computers need to include both an integrated battery as well as a removable battery in the computer itself. Even with both of these types of batteries included in a wearable computer, there is minimal impact to system weight – about 5 to 6 oz versus the 24 oz or more added by a “remote” external ruggedized battery solution. With this configuration, the wearable system can operate from the main battery and allow for a quick swap function, so the system can run in a backup mode from the integrated battery if needed.
This type of battery configuration can also operate from the external wire-powered interface, which can either be a battery or a power supply. To provide optimal reliability for military users, wearable computing systems need to provide highly integrated support for both main and backup batteries.
Customization for wireless functionalities important
The wireless capabilities of a wearable computer are a key consideration for military users, as this feature is the backbone of battlefield communications. Wireless functions need to be included in a wearable computer’s base platform while still allowing for some flexibility for integration of the wireless interfaces and their antennas. When flexibility is built into the design, application-specific wireless functionalities can be added.
To operate among many military platforms, integrated wireless functions should include WiFi 802.11, 50-channel GPS, and Bluetooth wireless. Modularity with the antenna interface can provide a localized, direct-attach antenna, or has the potential for remoting antennas or providing optional antenna functions – even with the wireless antenna controllers that are in the unit. The ability for the military to add extensible wireless modules is extremely important, as their specific application may have a need for a secure modem or a proprietary wireless link.
Rugged design paramount in extreme conditions
For the ground solider who trudges in extreme temperatures through water, dust, and dirt, any device worn on the body must be extremely rugged. When designing wearable computers destined for military use, size and weight are sometimes sacri-ficed to include more durable materials to increase ruggedness and reliability. For example, aluminum enclosures are used for increased durability and improve heat dissipation, whereas a wearable computer in a commercial application might be a lighter-weight plastic.
Advances in board designs for military wearable computers can increase ruggedness while at the same time reduce size. For example, when designing a board, engineers can incorporate all internal I/O without cabling or cable harnesses inside the unit to decrease the possible points of failure. In addition, boards can use a combination of rigid and flexible printed circuit boards from the main computer module to the external I/O. By eliminating internal connectors, the board is not only more rugged, but a smaller size.
To ensure a wearable device can endure battlefield situations, the computer must be designed to meet MIL-STD-810G environmental and MIL-STD-461F for conducted and radiated emissions/susceptibility standards. By adhering to these standards, wearable computers can sustain the extreme temperatures, vibration, shock, and EMI interference encountered by the warfighter.
Putting it all together for a complete package
In light of the military’s focus on wearable computers, military electronic designers have been stepping up to deliver rugged solutions for SWaP-constrained applications. For example, when Parvus and Eurotech engineers were designing the Zypad BR2000 wearable computer, the main objective was to deliver a low-power solution with device I/O interfaces for modularity and future scalability capable of operating in high-speed wired and wireless networks (Figure 2). The ability for the military to upgrade the system was an important design consideration as it enhances the wearable computer’s long-term viability. Because of its modularity, military users have the ability to choose from a family of processors, main memory, and integrated flash components without a redesign – simply by choosing from a family of SFF architectural modules.
Like many wearable computers, the BR2000 uses a purpose-built SFF PCB to optimize the size, weight, and ergonomics of the wearable application. The electronics leverage elements from the Catalyst-TC module from Eurotech (the Tunnel Creek version of the Atom Catalyst COM module) into a smaller form factor built specifically for the BR2000. Weighing in at less than 1.8 lbs (about 0.8 kg) when fully integrated with its rechargeable/removable battery, the device maintains a very small and lightweight mechanical package, similar in size to a portable cassette tape player.
Battlefield needs spur further innovation
Wearable computers are an integral component of the military’s net-centric warfare initiatives, and by leveraging the advancements of COTS components – such as processors, boards, wireless technologies, and batteries – wearable computers can evolve to meet the military’s warfighting needs. The end goal of wearable computers is to keep soldiers out of harm’s way and improve mission success. Accomplishing this presents engineers of wearable technology with some of the most intense design challenges in the COTS world. Not only do modern military customers demand that wearable computers withstand extreme conditions, but they must reduce SWaP – all without sacrificing performance. To meet these needs, manufactures must continue to innovate SFF board technology to handle the military’s demanding computing applications.
Eurotech North America firstname.lastname@example.org www.eurotech.com
Parvus Corporation email@example.com www.parvus.com