Simulating ideal assistive devices to reduce the metabolic cost of walking with heavy loads.
Simulating ideal assistive devices to reduce the metabolic cost of walking with heavy loads.
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DOI：
10.1371/journal.pone.0180320
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发表时间：
2017
期刊：
影响因子：
3.7
通讯作者：
Delp SL
中科院分区：
文献类型：
--
作者：
Dembia CL;Silder A;Uchida TK;Hicks JL;Delp SL
可穿戴机器人设备可以恢复和增强移动性。人们对设计降低行走代谢成本的装置越来越感兴趣;然而，设计者缺乏关于帮助哪些关节以及何时提供帮助的指导。为了帮助解决这个问题，我们使用肌肉骨骼模拟来预测假设的设备如何影响肌肉活动和负重行走时的代谢成本。我们研究了7种无质量器械，每种器械在一个方向（髋关节外展、髋关节屈曲、髋关节伸展、膝关节屈曲、膝关节伸展、踝关节跖屈或踝关节背屈）的一个自由度上提供不受限制的扭矩。我们使用OpenSim中的计算肌肉控制算法来寻找设备扭矩曲线，该扭矩曲线在跟踪无辅助负重行走的测量运动学的同时，使肌肉激活的平方和最小化。然后，我们检查了每种器械提供的代谢节省、相应的器械扭矩曲线以及由此产生的肌肉活动变化。我们发现髋关节屈曲、膝关节屈曲和髋关节外展装置比踝关节跖屈装置提供更大的代谢节省。髋关节外展器械的代谢节省与峰值瞬时正器械功率的比率最大，这表明前平面髋关节辅助可能是降低代谢成本的有效方法。总体而言，器械扭矩曲线通常与肌肉在无辅助情况下产生的相应净关节力矩不同，偶尔会超过净关节力矩，以减少其他自由度下的肌肉活动。许多器械会影响肢体其他部位的肌肉活动;例如，髋关节屈曲器械会影响跨越踝关节的肌肉。我们的研究结果可以帮助实验者决定在构建设备时要针对哪些关节运动，并可以为设备如何与肌肉骨骼系统相互作用提供直觉。这些模拟可以在网上免费获得，允许其他人复制和扩展我们的工作。
Wearable robotic devices can restore and enhance mobility. There is growing interest in designing devices that reduce the metabolic cost of walking; however, designers lack guidelines for which joints to assist and when to provide the assistance. To help address this problem, we used musculoskeletal simulation to predict how hypothetical devices affect muscle activity and metabolic cost when walking with heavy loads. We explored 7 massless devices, each providing unrestricted torque at one degree of freedom in one direction (hip abduction, hip flexion, hip extension, knee flexion, knee extension, ankle plantarflexion, or ankle dorsiflexion). We used the Computed Muscle Control algorithm in OpenSim to find device torque profiles that minimized the sum of squared muscle activations while tracking measured kinematics of loaded walking without assistance. We then examined the metabolic savings provided by each device, the corresponding device torque profiles, and the resulting changes in muscle activity. We found that the hip flexion, knee flexion, and hip abduction devices provided greater metabolic savings than the ankle plantarflexion device. The hip abduction device had the greatest ratio of metabolic savings to peak instantaneous positive device power, suggesting that frontal-plane hip assistance may be an efficient way to reduce metabolic cost. Overall, the device torque profiles generally differed from the corresponding net joint moment generated by muscles without assistance, and occasionally exceeded the net joint moment to reduce muscle activity at other degrees of freedom. Many devices affected the activity of muscles elsewhere in the limb; for example, the hip flexion device affected muscles that span the ankle joint. Our results may help experimentalists decide which joint motions to target when building devices and can provide intuition for how devices may interact with the musculoskeletal system. The simulations are freely available online, allowing others to reproduce and extend our work.
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