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Control Ergonomics for the Helmet-Mounted Display
In the course of its work, the panel did not address directly the question of control design for the helmet-mounted display. Because the functions to be controlled are not yet fully defined, it was not an appropriate question for the panel. However, our review of battlefield conditions, weapons deployment, and other matters related to the use of the helmet-mounted display generated some concerns on the part of panel members about the ergonomics of the controls to be used in the Land Warrior System. These concerns are covered briefly in this appendix.
In the battlefield setting of the past, the principal control used by the infantry soldier was the trigger on a gun. Even in relatively recent years, although weapons have become progressively more complicated, the controls used in the operation of these advanced weapons have been kept as simple as possible. With the advent of systems such as Land Warrior and its helmet-mounted display subsystem, however, vastly different levels of complexity have been introduced. As a result, the problem of control design for infantry weapon systems has become much more difficult than it once was.
Some of these new difficulties may be overcome by a reasonable adherence to the basic human factors principles that are available in handbook form (see e.g., Military Standard 1472-D). An expanded assembly of control design guidelines may also be needed to address the combination of sophisticated systems
with the environmental stresses of combat on the ground by individual dismounted soldiers.
Some of the design objectives will derive from decisions on the military doctrine that will stipulate the manner of use of the helmet-mounted display. Although such doctrine is not yet available, there are both analytical and empirical issues that can be raised that can give some orientation to the design effort.
As a point of departure and focus, the prime concern probably should be the digital computer component of the Land Warrior System. Even with this focus, there is some ambiguity about function. For example, it appears that one computer function will be to process signals-in real time-from higher command sources. One specific class of messages might cover the disposition of hostile forces in the immediate area. However, the precise form of such information is not yet known, and many possible message categories have yet to be stipulated. Nevertheless, it is clear that controls will be needed to regulate both the computer data processing and the display functions. It also seems clear that such controls are unlikely to be in the same family of devices that are used to regulate the channel, the brightness, and the contrast of video signals on the typical home television screen.
At least some of the adjustable attributes of the display should probably be preset and then maintained by the computer itself, with the additional provision for emergency manual override capabilities. This option is warranted on the grounds of minimizing task load on the soldier.
A related control design problem emerges from the prospect that the Land Warrior System can provide a choice of optical enhancements to the soldier. The key design question is not just the mode of actuation of one form of optical enhancement and the deactivation of another. It is that, given the presence of computer capability, can it be used to facilitate the soldier's adjustment to the changeover?
Another array of functions that are likely to be implemented in the Land Warrior System are location determination, route specification and ranging for direct and indirect fire. These functions stem from the capabilities provided by the global positioning system. Fortunately, the control requirement for these functions is relatively simple-activation/deactivation for location and route display. However, if a non-preplanned route is sought, something more akin to the query structure built into advanced personal computers might be needed. In other words, the soldier, as user, will need to be able to tell the computer both destination parameters and route information, such as a request for a route that does not involve visual exposure to an opposing force. Point-and-click procedures using a body-mounted trackball device may not be optimal for battlefield use because of
dexterity problems. Likewise, a voice-activated control has drawbacks in conditions of high background noise levels and in situations in which stealth is desired.
STIPULATIONS AND CRITERIA
Questions that are based on combat operations and that are subject to analytic resolutions include the following:
- What functions of the system require control?
- Should the exercise of control (of a particular function) be allocated to the individual soldier or to a computer?
- If allocated to a computer, should an override option be provided?
At some stage in the development of the Land Warrior System, attention should be focused on circumstances in which the dismounted soldier will face chemical, biological, and radiological weapons. Likewise, such features as automatic land mine detection should be considered.
A second set of questions will require research to resolve. Because of the complexity of the Land Warrior System, not only are there many single variables that need assessment by research but also many trade-off functions and interactions will require systematic study in a field setting. In that regard, there are basic questions about how a given control is to be put to use as well as additional crucial questions about how one mode of use relates to the other modes.
It seems unlikely that there is a single location (wrist, helmet, chest, belt, weapon stock, etc.) where the full complement of controls can be located without penalty. It seems equally unlikely that any one mode (keyboard, trackball, voice, etc.) will provide the ideal means of control. However, trying various arrangements in field or field-like conditions is a relatively straightforward test project that could lead directly to a minimally disruptive array of control locations.
Such an effort would be congruent with the thrust of the overall Land Warrior/helmet-mounted display program-which is to give the dismounted soldier as much of a tactical advantage as possible while not adding to his problems. This general goal also leads to some reasonable specifications for the designers of the controls.
First, the controls should be kept as simple (and rugged) as possible. They should also be protected from inadvertent activation-by the soldier or by obstructions in the environment-but at the same time should be easily and quickly accessible. Whenever possible, there should be strong cues to the function over which the control presides. Such cues include location in sets, proximity to the device being controlled, and some easy abstraction such as a shape cue or a color coding that is not ambiguous (i.e., red = stop).
These and other standard ergonomic stipulations allow great discretion on the part of the designers-so they should not be a source of constraints or inhibi-
tions. However, no matter how elaborate the design guidance, there will always remain some uncertainties related to the specific requirements generated by the overall system concept and its interactions with the populations of human users and the contexts within which use will take place. Uncertainties that are system-specific are the warrant for sustaining a strong research, test, and evaluation capability. Many trade-off studies will be needed before the Land Warrior equipment is ready to issue to the troops. The framework for such research should be a strong user orientation. Resolving the uncertainties of control design should be driven by the soldier' s sense of what is needed, useful, and preferable when going into combat.