Hierarchical actuators are comprised of multiple individual actuator elements arranged into a system, resulting in improved and expanded performance. Natural muscle tissue is a complex and multi-level example of hierarchical actuation, with its hierarchy spanning from the micrometer to the centimeter scale. In addition to a hierarchical configuration, muscle tissue exists in varying geometric arrangements. Pennate muscle tissue, denoted by its characteristic fibers extending obliquely away from the muscle tissue line of action, leverages geometric complexity to transform the relationship between fiber inputs and muscle tissue outputs. In this paper, a bioinspired hierarchical pennate actuator is detailed. This work expands on previous pennate actuator studies by deriving constitutive force, contraction, and stiffness models for a general pennate actuator, where the constituent fibers can be constructed from any linear actuator. These models are experimentally validated by studying a pennate actuator with McKibben artificial muscles constituting the actuator fibers. McKibben artificial muscles are used because they have a high force-to-weight ratio and are inexpensive to construct, making them an attractive candidate for hierarchical actuators and mobile robotics. Using the derived constitutive models, general pennate actuator performance is better understood by analyzing the transmission ratio, blocked force, and free contraction. Loaded contractions and stiffness during isotonic and isobaric contractions are also explored. The results allow for informed design decisions and an understanding of the associated tradeoffs when recreating the remarkable properties of pennate musculature. Future work will leverage the results of this paper to create an adaptive pennate actuator that is capable of changing configuration in response to force, contraction and stiffness demands.

中文翻译：

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三角型执行器：力，收缩力和刚度。

分层执行器由布置在系统中的多个单独的执行器元件组成，从而提高了性能并扩展了性能。天然肌肉组织是一个复杂且多层次的层次驱动示例，其层次从微米到厘米。除了层次结构外，肌肉组织还存在各种几何结构。三角肌组织以其特征性纤维倾斜地延伸远离肌肉组织作用线来表示，它利用几何复杂性来转换纤维输入和肌肉组织输出之间的关系。在本文中，详细介绍了受生物启发的分层三角执行器。通过推导本构力，收缩力，普通的半圆形执行器的刚度和刚度模型，其中组成纤维可以由任何线性执行器构成。这些模型通过研究用McKibben人造肌肉构成致动器纤维的三角肌致动器进行实验验证。之所以使用McKibben人造肌肉，是因为它们具有很高的力重比，而且构造成本低廉，因此非常适合用于分层执行器和移动机器人。使用派生的本构模型，可以通过分析传动比，阻挡力和自由收缩来更好地理解一般的三角执行器性能。还研究了等张和等压收缩过程中的载荷收缩和刚度。结果可以使您在重现戊二酸肌肉组织的显着特性时做出明智的设计决策并了解相关的权衡取舍。未来的工作将利用本文的结果来创建一个自适应的半主动执行器，该执行器能够根据力，收缩和刚度的要求而改变配置。