Effects of Bladder Geometry in Pneumatic Artificial Muscles
Effects of Bladder Geometry in Pneumatic Artificial Muscles
复制标题
膀胱几何形状对气动人工肌肉的影响
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
Ephrahim Garcia
中科院分区：
文献类型：
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作者：
E. Ball;Ephrahim Garcia
为特定应用设计最佳气动肌肉需要超弹性膀胱的精确模型以及它如何影响收缩力。在此，我们提出了不同膀胱预应变和壁厚的人造肌肉驱动特性的模型和实验数据。测试确定拉伸和收缩过程中的准静态力-长度关系，对于未拉伸的膀胱长度等于拉伸肌肉长度的55%，66%和97%，以及两种不同的壁厚的肌肉。执行器的力和最大收缩长度被发现强烈地依赖于预应变和橡胶的厚度，使得现有的模型不适合选择气囊的几何形状。采用一种新颖的厚壁管计算方法来考虑气囊的非线性弹性特性，提出了一种从几何参数更好地预测力长度特性的模型。它包括纵向拉伸膀胱所产生的轴向力，也描述了肌肉径向扩张所产生的环向应力，这种环向应力部分抵消了施加在网格上的内部流体压力。这种有效的压力减少影响轴向肌力和网眼-膀胱摩擦。橡胶气囊被建模为Mooney-Rivlin不可压缩固体。由网格产生的轴向力直接由接触力而不是由势能得到。将膀胱建模为薄壁管与壁厚的实验数据非常接近，但发现厚壁膀胱模型对于解释预应变的影响是必要的。
Designing optimal pneumatic muscles for a particular application requires an accurate model of the hyperelastic bladder and how it influences contraction force. We present here modeling and experimental data on the actuation properties of artificial muscles constructed with varying bladder pre-strain and wall thickness. The tests determine quasi-static force-length relationships during extension and contraction, for muscles constructed with unstretched bladder lengths equal to 55%, 66%, and 97% of the stretched muscle length, and two different wall thicknesses. Actuator force and maximum contraction length are found to depend strongly on both the pre-strain and the thickness of the rubber, making existing models inadequate for choosing bladder geometry. A model is presented to better predict force-length characteristics from geometric parameters, using a novel thick-walled tube calculation to account for the nonlinear elastic properties of the bladder. It includes axial force generated by stretching the bladder lengthwise, and it also describes the hoop stress created by radial expansion of the muscle that partially counteracts the internal fluid pressure exerted outward on the mesh. This effective reduction in pressure affects both axial muscle force and mesh-on-bladder friction. The rubber bladder is modeled as a Mooney-Rivlin incompressible solid. The axial force generated by the mesh is found directly from contact forces rather than from potential energy. Modeling the bladder as a thin-walled tube gives a close match to experimental data on wall thickness, but a thick-walled bladder model is found to be necessary for explaining the effects of pre-strain.