Invariant Hip Moment Pattern While Walking With a Robotic Hip Exoskeleton
By Lewis, Cara L.; Ferris, Daniel P.; Journal of Biomechanics, Volume 44, Number 5, pages 789-793Publication Date: March 15, 2011
Study tested the hypothesis that people reduce net muscle moments about their joints when robotic assistance is provided. This reduction in muscle moment results in a total joint moment, of muscle plus exoskeleton, that is the same as the moment without the robotic assistance despite potential differences in joint angles. A pneumatically powered hip exoskeleton was created to assist hip flexion during gait, consisting of a prefabricated hip brace modified to include a pneumatic actuator with two cylinders providing external joint torques. A tension/compression load cell placed in series with the pneumatic cylinders quantified assistance provided by the robotic exoskeleton. Eight participants without disabilities trained with the orthotic while walking on a force-measuring treadmill. Participants walked with the exoskeleton unpowered for 10 minutes and providing hip flexion assistance for 30 minutes. The root mean squared difference (RMSD) was calculated between the average of data from the unpowered condition and the last 15 minutes of the powered condition. After completing three 30-minute training sessions, the hip exoskeleton provided 27 percent of the total peak hip flexion moment during gait. Despite this substantial contribution from the orthotic, participants walked with a total hip moment pattern that was almost identical and more similar to the unpowered condition than the hip angle pattern, showing hip moment RMSD 0.027 and angle RMSD 0.134. The angle and moment RMSD were not different for the knee and ankle joints. These findings contribute to the understanding of how people adapt to walking with robotic devices.
Published by: Elsevier Inc. (Website:http://www.elsevier.com)
Link to text: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3075111/?tool=pmcentrez
