Background

Leg muscle fatigue is the most important factor that affects walking endurance. Considering the legs act as actuators in alternate contact with the ground during walking, the ground reaction force (GRF) of each leg can indirectly reflect the strength of leg muscles. However, it is not clear how the elastically-suspended backpack (ESB) affects GRF of each leg during human level walking.

Research question

How is ESB related in GRF of each leg during walking, and how do multiple variables (stiffness and damping of ESB, load mass, walking speed) affect GRF?

Methods

An extended bipedal walking model (EBW) with a spring-mass-damping system was proposed to predict the GRF of each leg. In order to evaluate the prediction effect of the model, seven healthy subjects were recruited to attend the experiments using our backpack prototype and the GRFs data was compared. Each subject walked under 12 conditions (load states: locked or unlocked, walking speed: 3.6 km/h, 4.0 km/h, 4.5 km/h, 5.0 km/h, 5.5 km/h, 6.0 km/h).

Results

Results showed that the model could quantitatively predict experimental GRFs over the whole gait cycle ($R^2\ge 0.9628$) and the characteristic forces (two peak forces and one trough force) were close to the experimental data (average predicted accuracy 93.7 %). The model can reflect relationships between variables and GRF. The relationships showed that an apparent tradeoff exists among the three characteristic forces, and the ESB can produce positive or negative effect under different variables.

Significance

This work could help us understand the experimental GRF phenomena, especially the contradictory experimental phenomenon caused by the different parameters. It could also help designers optimize structural parameters of ESB for excellent effects on human. The ESBs with excellent performance can be wildly used in military and tourism.

中文翻译：

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预测弹性悬挂背包的地面反作用力的模型。

背景

腿部肌肉疲劳是影响步行耐力的最重要因素。考虑到腿在行走过程中充当与地面交替接触的促动器，因此每条腿的地面反作用力（GRF）可以间接反映腿部肌肉的力量。然而，尚不清楚弹性悬浮背包（ESB）在人的水平行走过程中如何影响每条腿的GRF。

研究问题

ESB与步行过程中每条腿的GRF有何关系，多个变量（ESB的刚度和阻尼，负载质量，步行速度）如何影响GRF？

方法

提出了具有弹簧质量阻尼系统的扩展双足步行模型（EBW），以预测每条腿的GRF。为了评估模型的预测效果，使用我们的背包原型招募了七名健康受试者参加实验，并对GRFs数据进行了比较。每个受试者在12种条件下行走（负荷状态：锁定或解锁，行走速度：3.6 km / h，4.0 km / h，4.5 km / h，5.0 km / h，5.5 km / h，6.0 km / h）。

结果

结果表明，该模型可以定量预测整个步态周期中的实验性GRF（${\mathrm{[R}}^2\ge 0.9628$）和特征力（两个峰值力和一个低谷力）都接近实验数据（平均预测准确度为93.7％）。该模型可以反映变量与GRF之间的关系。这些关系表明，这三个特征力之间存在明显的权衡，ESB在不同变量下可以产生正效应或负效应。

意义

这项工作可以帮助我们理解实验的GRF现象，尤其是由不同参数引起的矛盾实验现象。它还可以帮助设计人员优化ESB的结构参数，从而对人体产生出色的效果。性能卓越的ESB可广泛用于军事和旅游业。