弹性背包振动模式优化及肌肉特性分析

负重行走是与人类文明长期共存的一个问题。外骨骼的助力方式在控制方
面， 有难以实现人机融合等问题。 弹性背包的方式在提高负重行走效能过程中，
既不会对人体造成伤害， 又穿戴方便。现有的弹性背包在设计过程中多采用减
小负载作用于人体的力的方式，对于人体肌肉特性考虑较少。 在行走过程中，
人在蹬地时刻地面反力出现极大值， 踝关节正功功率达到最大， 并且小腿肌肉
群主要做主动的向心收缩， 这可能是重负行走的短板。 因此， 本论文从降低人
体蹬地时刻对肌肉发力的需求出发， 研制一款变刚度弹性背包，并对其振动模
式进行优化，提高负重行走效能， 论文完成的主要工作有：
结合行走肌肉做功特性， 提出了通过调节负载与人体在垂直方向振动的相
位差的弹性背包设计方法。 基于蹬地时刻为肌肉发力能力的短板和简化弹性背
包为质量弹簧阻尼模型， 调节负载与人体在垂直方向振动位移的相位差， 减小
在蹬地时刻负载作用于人体的力， 提高负重行走能力。
提出了不同步速条件下，能够实现期望相位差的变刚度弹性背包系统刚度
和阻尼设计方法。 讨论了期望步速和负载与人体振动相位差的变化范围的选择；
分析了变刚度的机械结构带来的对系统的刚度和阻尼设计的限制； 通过仿真得
到可以实现理想相位差和步速范围的阻尼和每个阻尼对应的刚度变化范围。
基于理论阻尼和刚度， 设计了一种采用变节距弹簧的， 系统刚度可调弹性
背包系统。 通过压缩变节距弹簧的方式改变系统的刚度，进而改变负载与人体
在垂直方向上振动的相位差； 基于质量弹簧阻尼模型和变刚度系统的静力学分
析，对系统刚度进行分配，并设计了变刚度弹簧和普通弹簧。 搭建了驱动系统。
测试了弹性背包系统参数， 并验证了弹性背包可以降低行走蹬地力及肌肉
激活情况。 通过实验测试负载和人体振动的幅值， 二者运动的相位差和人体行
走的步频，计算弹性背包系统的阻尼为 26.83Ns/m， 数值在可行阻尼范围中，并
以此为依据设计系统刚度。 变刚度弹性背包可以实现负载与人体振动 60~110°
相位差的变化。 不同相位差条件下受试者蹬地力和肌肉激活情况均明显降低且
减小量不同
 

Walking with load is a problem that coexists with human civilization for a long
time. The exoskeleton has difficulty in controlling man-machine fusion when
assisting. The elastic-suspended backpack does not hurt the body and is easy to wear
when improving walking performance. The key of existing elastic-suspended
backpacks is to reduce amplitude of the force acting on the human body, while human
muscles’ own characteristics have not been considered a lot. When the ankle joints
push off during the gait cycle, the ground reaction force and the ankle power reach
peaks, and the main muscles of shanks do lots of concentric activation, which may be
the weakness of walking capacity with load. Therefore, in order to reduce muscle
power demand during pushing-off, this paper aims at developing an elastic-suspended
backpack with variable stiffness and optimizing its vibration mode to improve the
walking capacity with load. The main contents of this dissertation are as follows:
Combined with the muscle’s characteristics during walking, an elasticsuspended backpack design method of changing the phase difference of vertical
oscillation between load and body is proposed. Based on that the pushing-off is the
weakness of the muscle strength and the mass-spring-damping model, the phase
difference between the load and the human body in the vertical motion is adjusted to
reduce the force acting on the human body when pushing off, improving the walking
capacity with load.
The optimization of stiffness and damping in variable stiffness elastic-suspended
backpack for the expected phase difference under different speeds is proposed. The
selection of the range of desired speed and the phase difference is stated. The
limitations of the stiffness and damping design brought about by the mechanical
structure of the variable stiffness spring are analyzed. The damping range that can
achieve the ideal range of phase difference and the speed and the range of the stiffness
corresponding to each damping is obtained through simulation.
Based on the theoretical damping and stiffness, the elastic-suspended backpack
system with variable pitch spring is designed, which can change the system stiffness.
The variable pitch spring is used to change the stiffness of the system, changing the
phase difference between the load and the body in the vertical motion. Based on the
static analysis of the system, the stiffness of the system is distributed, and a variable
stiffness spring and an ordinary spring are designed. The drive system is built.
The system parameters of the elastic-suspended backpack were tested and it’s
verified that it can reduce the ground reaction force and the muscle activation. Thedamping of the elastic-suspended backpack system are calculated by experimentally
testing the amplitude of the load and human vibration, the phase difference between
the body and load and the walking frequency of the carrier, which is 26.38Ns/m and
is in the feasible damping range. The result is used to design the system stiffness. The
elastic-suspended backpack can realize the change of phase difference between the
load and the body vibration of 60~110° . Under different phase difference conditions,
the subject's ground reaction force and muscle activation were significantly reduced
and the amount of reduction was different.
 

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