Exoskeleton Power and Torque Requirements Based on Human Biomechanics

Report No. ARL-TR-2764
Authors: Harrison P. Crowell III, Angela C. Boynton, and Michael Mungiole
Date/Pages: November 2002; 53 pages
Abstract: This report provides baseline estimates of the power and torque requirements for the lower limbs of an exoskeleton1 for two hypothetical dismounted missions. The missions are ?movement to contact? and ?clear a building?. The power and torque estimates can be used to size key components such as the power supply and actuators. The estimates are based on human biomechanical data reported in journal articles and technical reports. The variability of biomechanical measures and the assumptions and potential errors involved in data collection and processing are discussed. The accuracy of the joint angle, torque, and power output variables is estimated to be within 20% of the reported values. In the use of these data, several assumptions are made regarding the equivalence of the exoskeleton and a human. To obtain peak power profiles for the hypothetical missions, each mission was broken into the tasks (walking, jogging, kneeling, jumping, etc.) that the soldier (50th percentile, by body mass, male carrying a load) performed. Then, the total power requirement over one cycle of each task was calculated, and the peak and average powers required during that cycle were identified. Combining the peak power requirements of the tasks in a chronological sequence results in a peak power profile for the entire mission. For the movement-to-contact mission, a nearly constant peak power of 500 W is required, with short-term requirements as great as 5.5 kW. For the clear-building mission, a nearly constant peak power of 400 to 700 W is required, with short-term requirements of 2 to 3.5 kW.
Distribution: Approved for public release
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Last Update / Reviewed: November 1, 2002