Historically, the displays deployed in military vehicles have been simple monitors, acting as an interface to an onboard system. That’s no longer good enough. As military vehicles are equipped with more and more technology, space — not to mention weight and power — is becoming scarce. Mono-functional systems are out; multifunctional systems are in, whether you’re designing new vehicles or retrofitting existing vehicles.
The VICTORY Architecture
That paradigm shift is nowhere better illustrated than in the US Army’s VICTORY (Vehicular Integration for C4ISR/EW Interoperability) architecture, which sees the elimination of duplication in functionality. In the past, each new subsystem brought with it its own processing capability, its own data storage, and often its own display. VICTORY looks to a future in which, by eliminating this duplication, significant savings can be made in size, weight and power (SWaP), not to mention cost. At its heart is a highly flexible, highly redundant, high-speed network — using Gigabit Ethernet — which provides common access to every attached device, and which connects sensors and storage to processors and displays.
The military vehicle onboard display of the future needs to respond to this change. Not only must it be rugged — capable of robust, reliable operation in environments that are subject to extremes of shock, vibration, heat, contaminants and so on — but it must, so far as it makes sense, be more than a display. There is, in fact, no reason why it cannot include the embedded computing capability needed for many of a vehicle’s functions. The question becomes: what does that embedded computing capability need to be capable of doing?
The majority of embedded single board computers deployed in military vehicles today are based on Intel’s Core 2 Duo processor architecture, recently refreshed with the announcement of the Intel’s Ivy Bridge technology.
GPUs Complement “Traditional” Processors
Increasingly, however, “general purpose” processors are being complemented by powerful graphics processors from companies like NVIDIA. The reason? The massively parallel architecture that makes a GPU (graphics processing unit) ideal for delivering fast moving, photo-realistic images to a screen is no less ideal for many of the most challenging military/aerospace applications that can equally leverage that parallelism, such as video and image- or radar processing. In an ideal world, such a capability could be made available within an in-vehicle display where processing requirements are particularly onerous, or it could be omitted for deployments that demand less processing power.
Integrating a single board computer within a display’s housing, in much the same way as a consumer-grade “all-inone” PC does, is the way forward, saving valuable space and cost. The real challenge, though, is how to ensure the display is sufficiently rugged to withstand the rigors of battlefield deployment.
If anything, the display, — including its housing and processing capability, — must be even more rugged than the embedded computing subsystems deployed aboard the vehicle (Figure 2). Whereas the rest of the system is often tucked away in unused corners, the display, by definition, is “front and center”, susceptible not only to the challenges of the battlefield environment, but also to inadvertent collisions with personnel in cramped surroundings, and to heavy-handed operation.
The single board computer embedded within the display will be designed and built using the same principles and in many cases the same components, as those applied to any single board computer destined for a harsh and power/cooling-constrained environment. It should be just as capable of having, for example, a conformal coating applied during manufacture in order to increase its ability to withstand contaminants.
Ruggedizing The Screen
But what of the display itself? Glass needs to be chosen that is a suitable thickness for its area, and should then be chemically treated to ensure that it is robust against the worst of the physical abuses it will encounter in its inservice life. In addition to chemical treatment for robustness, the glass will also be treated to minimize reflections and to provide EMI integrity. All of these processes need to be of the highest standard to ensure that the LCD image is not degraded as it passes through the glass, because even the slightest hesitation in interpreting the on-screen image is intolerable.
There are differing approaches to the problem of protecting the LCD behind the glass. One of those is to leave an air gap between the various layers in the display stack, from front glass (which is susceptible to impact) and the LCD itself. The downsides of this approach are serious from the perspective of the user. First, any residual moisture in the assembly will inevitably find its way into the gap where it will condense on the colder surface, resulting in visible droplets of water that affect the image quality. Second, the thickness of the front glass, coupled with the coefficient of refraction, can give rise to a significant parallax error, which is a major problem when using a touchscreen. When eye and fingertip are perpendicular to the point on the LCD displaying the relevant symbology, parallax is not an issue, but as the eye moves from the perpendicular it becomes increasingly difficult to judge the correct point on the touchscreen to match the onscreen symbology.
There are strategies to deal with the moisture problem, including incorporating desiccants and purging the final assembly, but these are not reliable longterm solutions over the life of the unit. The parallax issue remains, however, and once again the need for instantaneous action on the battlefield means that it is unacceptable.
An alternative strategy is to bond the layers of the display stack. This is not without its challenges, which include eliminating impurities, ensuring that air-bubbles do not become trapped in the assembly, and preventing delamination over the lifetime of the product. Good component selection and bonding- compound selection are key to the solution, but a rigorous manufacturing process is vital to ensure uniform application of the bonding agent in a clean room environment.
While there is significant investment in time and equipment required to achieve the bonded solution, there can be no substitute for the resulting optical quality, yielding a bright display with no compromising visual artifacts.
It is a given, especially in light of the proliferation of such devices in day-today life, that the in-vehicle display of the future will feature touchscreen technology.
The designer has three choices: resistive, capacitive and infrared. While some of the technologies available in the commercial marketplace have attractions for the user experience — for example, the user interface revolution caused by the multi-touch capacitive touchscreen on the Apple iPhone — most have serious downsides for the vehicle market.
Capacitive touchscreens offer some tantalizing opportunities, but these are difficult to set up for use with both bareand gloved-hands. Additionally, some capacitive technologies, which offer the smoothest user experience in commercial applications can be bad EMC emitters, something that is unacceptable in land vehicle design. Similarly, infrared touchscreens offer some advantages, but these are more than outweighed by the combatant-threatening problems of the vehicle becoming an infrared emitter at nighttime.
In a moving vehicle (Figure 3), making an accurate actuation via the touchscreen can be a significant challenge. Application design can ease that challenge by ensuring adequate spacing of onscreen activated areas or buttons, but that is only part of the story. Requiring a positive pressure for activation can prevent false actuations, and this is one of the key characteristics of resistive touchscreen technology, which is preferred for in-vehicle rugged displays.
The potential applications for these highly intelligent, extremely rugged invehicle displays are wide-ranging from embedded training to terrain visualization, from digital mapping to battlefield communications and management, from signals intelligence (SIGINT) to situational awareness, including 360- degree video stitching. The important change, though, is that a new generation of rugged displays is becoming available that incorporate the same amount of processing power as would previously have been configured in a discrete, standalone box, thus saving vital space, weight and power.
Integrated With The Network
Moreover, with modern vehicles now having large numbers of electro-optic sensors, providing the display not only with processing capability but also a 10 Gigabit Ethernet interface means that it is possible to connect the display directly to the video backbone of the vehicle and subscribe directly to those channels of interest.
As with all embedded computing solutions, the design of these displays demands in-depth understanding not only of the application, but also how that application will be deployed, as well as by what kind of personnel, operating under what kind of constraints, and in what kind of environment it will be used. Few, if any, elements of an in-vehicle embedded computing system have a more vital role to play than the display, meaning the choices made in its design are nothing less than critical.