on developing load-carrying devices that will increase the speed, endurance, and load-carrying capacity of soldiers in combat environments. This program, like the microclimate cooling efforts, is in its early development phase, and the committee did not analyze the relative merits of solutions on the drawing boards. The committee does, however, document here its observations on preliminary approaches presented to it by DARPA (Main, 2003). Specific target applications include moving heavy loads over rough terrain, bearing heavy weapons or equipment, carrying and powering breaching equipment, and using the exoskeleton as a platform for increased body armor. The vision is to utilize such devices with power supplies that are energetically autonomous of other power sources. Such exoskeleton devices must mimic human motions and provide close human/machine integration. Human/machine interfaces must provide for transparent control of the exoskeleton over extended periods of operation.

Since the loads carried by rifle-squad personnel during a 72-hr mission are projected to range from 140 pounds for a rifleman to 185 pounds for an antitank specialist, such human augmentation is clearly desirable. Developing augmentation devices that are both compatible with and comparable to human capabilities is a daunting task. Human muscles provide large motions and high repetition rates. Various power sources are compared in Figure 4-1 on the basis of the stress/ strain product capabilities versus their frequency response capabilities.

As can be seen in Figure 4-1, human muscle provides a combination of high-frequency and high stress/strain activity.

FIGURE 4-1 Comparison of various means of exoskeletal actuation on the basis of stress/strain product capabilities. SOURCE: Main, 2003.