Modeling of Resistive Forces and Buckling Behavior in Variable Recruitment Fluidic Artificial Muscle Bundles
Modeling of Resistive Forces and Buckling Behavior in Variable Recruitment Fluidic Artificial Muscle Bundles
复制标题
DOI：
10.3390/act10030042
复制
发表时间：
2021-03-01
期刊：
影响因子：
2.6
通讯作者：
Bryant, Matthew
中科院分区：
文献类型：
--
作者：
Kim, Jeong Yong;Mazzoleni, Nicholas;Bryant, Matthew
流体人工肌肉（FAM），也称为 McKibben 执行器，是一类纤维增强的软执行器，可以通过气动或液压加压来产生类似肌肉的收缩和产生力。当多个 FAM 并行捆绑在一起并选择性加压时，它们可以充当具有仿生可变招募能力的多室执行器。可变募集束由运动单位 (MU)（多个 FAM 组成的组）组成，这些运动单位根据力需求独立加压，类似于生物肌肉中肌纤维组的顺序募集方式。当活动 FAM 收缩时，非活动/低压单元被压缩，导致它们向外弯曲，从而增加执行器的空间包络。此外，压缩超过其单独自由应变的 FAM 会施加一个与主动 FAM 的整体力输出相反的力。在本文中，我们提出了一个模型来量化在不活动和低压 FAM 中观察到的阻力，并研究其对可变招募束性能的影响。阻力行为被分为屈曲后和塌陷后区域，并设计了分段模型。提出了一种基于经验的校正方法来改进模型以拟合实验数据。对具有电阻效应的束的分析揭示了可变募集束所特有的现象，定义为自由应变梯度反转。
Fluidic artificial muscles (FAMs), also known as McKibben actuators, are a class of fiber-reinforced soft actuators that can be pneumatically or hydraulically pressurized to produce muscle-like contraction and force generation. When multiple FAMs are bundled together in parallel and selectively pressurized, they can act as a multi-chambered actuator with bioinspired variable recruitment capability. The variable recruitment bundle consists of motor units (MUs)-groups of one of more FAMs-that are independently pressurized depending on the force demand, similar to how groups of muscle fibers are sequentially recruited in biological muscles. As the active FAMs contract, the inactive/low-pressure units are compressed, causing them to buckle outward, which increases the spatial envelope of the actuator. Additionally, a FAM compressed past its individual free strain applies a force that opposes the overall force output of active FAMs. In this paper, we propose a model to quantify this resistive force observed in inactive and low-pressure FAMs and study its implications on the performance of a variable recruitment bundle. The resistive force behavior is divided into post-buckling and post-collapse regions and a piecewise model is devised. An empirically-based correction method is proposed to improve the model to fit experimental data. Analysis of a bundle with resistive effects reveals a phenomenon, unique to variable recruitment bundles, defined as free strain gradient reversal.