Sherman Michael A, Seth Ajay, Delp Scott L
Department of Bioengineering, Stanford University, Stanford, California 94305.
Departments of Bioengineering and Mechanical Engineering, Stanford University, Stanford, California 94305.
Proc ASME Des Eng Tech Conf. 2013 Aug;2013. doi: 10.1115/DETC2013-13633.
Biomechanics researchers often use multibody models to represent biological systems. However, the mapping from biology to mechanics and back can be problematic. OpenSim is a popular open source tool used for this purpose, mapping between biological specifications and an underlying generalized coordinate multibody system called Simbody. One quantity of interest to biomechanical researchers and clinicians is "muscle moment arm," a measure of the effectiveness of a muscle at contributing to a particular motion over a range of configurations. OpenSim can automatically calculate these quantities for any muscle once a model has been built. For simple cases, this calculation is the same as the conventional moment arm calculation in mechanical engineering. But a muscle may span several joints (e.g., wrist, neck, back) and may follow a convoluted path over various curved surfaces. A biological joint may require several bodies or even a mechanism to accurately represent in the multibody model (e.g., knee, shoulder). In these situations we need a careful definition of muscle moment arm that is analogous to the mechanical engineering concept, yet generalized to be of use to biomedical researchers. Here we present some biomechanical modeling challenges and how they are resolved in OpenSim and Simbody to yield biologically meaningful muscle moment arms.
生物力学研究人员经常使用多体模型来表示生物系统。然而，从生物学到力学再返回的映射可能存在问题。OpenSim是用于此目的的一种流行的开源工具，它在生物规格与一个名为Simbody的基础广义坐标多体系统之间进行映射。生物力学研究人员和临床医生感兴趣的一个量是“肌肉力臂”，它是衡量肌肉在一系列构型上对特定运动做出贡献的有效性的指标。一旦建立了模型，OpenSim可以自动为任何肌肉计算这些量。对于简单情况，此计算与机械工程中的传统力臂计算相同。但是一块肌肉可能跨越多个关节（例如手腕、颈部、背部），并且可能在各种曲面上遵循复杂的路径。一个生物关节可能需要多个物体甚至一个机构才能在多体模型中准确表示（例如膝盖、肩膀）。在这些情况下，我们需要对肌肉力臂进行仔细定义，它类似于机械工程概念，但经过推广后对生物医学研究人员有用。在这里，我们介绍一些生物力学建模挑战以及它们在OpenSim和Simbody中是如何解决的，以产生具有生物学意义的肌肉力臂。
