Young Aaron J, Foss Jessica, Gannon Hannah, Ferris Daniel P
Woodruff School of Mechanical Engineering, Georgia Institute of Technology , Atlanta, GA , USA.
Department of Biomedical Engineering, University of Michigan , Ann Arbor, MI , USA.
Front Bioeng Biotechnol. 2017 Mar 8;5:4. doi: 10.3389/fbioe.2017.00004. eCollection 2017.
A broad goal in the field of powered lower limb exoskeletons is to reduce the metabolic cost of walking. Ankle exoskeletons have successfully achieved this goal by correctly timing a plantarflexor torque during late stance phase. Hip exoskeletons have the potential to assist with both flexion and extension during walking gait, but the optimal timing for maximally reducing metabolic cost is unknown. The focus of our study was to determine the best assistance timing for applying hip assistance through a pneumatic exoskeleton on human subjects. Ten non-impaired subjects walked with a powered hip exoskeleton, and both hip flexion and extension assistance were separately provided at different actuation timings using a simple burst controller. The largest average across-subject reduction in metabolic cost for hip extension was at 90% of the gait cycle (just prior to heel contact) and for hip flexion was at 50% of the gait cycle; this resulted in an 8.4 and 6.1% metabolic reduction, respectively, compared to walking with the unpowered exoskeleton. However, the ideal timing for both flexion and extension assistance varied across subjects. When selecting the assistance timing that maximally reduced metabolic cost for each subject, average metabolic cost for hip extension was 10.3% lower and hip flexion was 9.7% lower than the unpowered condition. When taking into account user preference, we found that subject preference did not correlate with metabolic cost. This indicated that user feedback was a poor method of determining the most metabolically efficient assistance power timing. The findings of this study are relevant to developers of exoskeletons that have a powered hip component to assist during human walking gait.
动力下肢外骨骼领域的一个广泛目标是降低行走的代谢成本。脚踝外骨骼通过在站立后期正确施加跖屈扭矩成功实现了这一目标。髋部外骨骼在步行步态中具有辅助屈伸的潜力，但最大程度降低代谢成本的最佳时机尚不清楚。我们研究的重点是确定通过气动外骨骼对人体受试者施加髋部辅助的最佳辅助时机。十名未受损的受试者穿着动力髋部外骨骼行走，并使用简单的脉冲控制器在不同的驱动时机分别提供髋部屈伸辅助。髋部伸展时，受试者平均代谢成本降低幅度最大的是在步态周期的90%（刚好在足跟接触之前），髋部屈曲时是在步态周期的50%；与穿着无动力外骨骼行走相比，这分别导致代谢降低了8.4%和6.1%。然而，屈伸辅助的理想时机因受试者而异。当为每个受试者选择最大程度降低代谢成本的辅助时机时，髋部伸展的平均代谢成本比无动力状态低10.3%，髋部屈曲低9.7%。考虑到用户偏好，我们发现受试者的偏好与代谢成本无关。这表明用户反馈不是确定最具代谢效率的辅助动力时机的好方法。这项研究的结果与在人类步行步态中具有动力髋部组件以提供辅助的外骨骼开发者相关。
