NONEQUILIBRIUM IN THE TRANSLATIONAL EQUATIONS OF MOTION

许多生物力学分析的基础一直是逆动力学 通过使用刚体力学。平动方程 一项动议规定，作用在一个系统上的所有外力的总和 刚体的质量/加速度之和必须等于每个物体的质量/加速度之和 产品这种关系维持的程度取决于 基于几何和段质量分布模型的有效性， 关于段刚度的假设，以及 个别段加速估计。我们的近期目标是 评估与翻译实施相关的错误 十五段刚体模型的运动方程 在步态中形成。我们的目标是提高我们三个- 三维全身模型。我们计划使用测量过的地面反应 力（GRF）作为标准，用于比较节段 质量/加速度产品，使用各种数据收集计算， 分析技术。全身模型由手、前臂、 足部、小腿、大腿、骨盆、躯干/腹部和头部，所有 被建模为规则的几何形状。人体测量是 为每个主题制作个性化的片段。无源红外 运动分析系统用于收集节段运动学，GRF 使用两个应变计测力板获得。残留误差 在每个采样时刻计算为 减去所有分段质量/加速度乘积之和， 以体重的百分比表示。收集了17个试验 5名正常男性。 垂直轴的平均RMS残差为6.1 +/- 4.4%， 前/后轴为1.3%， 内侧/外侧轴。被RMS和系综平均过程掩盖， 垂直方向的残差达到43% 在脚着地时的体重这些数据表明，我们的几何 模型产生了可接受的“非平衡”水平，除了在脚 罢工将对运动学数据的影响进行进一步研究 残差最小化处理。

The basis of many biomechanical analyses has long been inverse dynamics through the use of rigid body mechanics. Equations of translational motion stipulate that the sum of all external forces acting on a system of rigid bodies must equal the sum of each body's mass/acceleration product. The extent to which this relationship is maintained depends upon the validity of the geometric and segment mass distribution model, the assumptions regarding segment stiffness, and the accuracy of the individual segment acceleration estimates. Our immediate objective is to evaluate the error associated with the implementation of translational equations of motion in a fifteen segment rigid body model of the human form during gait. Our goal is to improve the accuracy of our three- dimensional full-body model. We plan to use measured ground reaction forces (GRF) as criteria against which to compare the sum of segmental mass/acceleration products, calculated using various data collection and analysis techniques. The full-body model is comprised of hand, forearm, foot, shank, thigh, pelvis, trunk/abdomen, and head segments, all modeled as regular geometric shapes. Anthropometric measurements are made to individualize segments for each subject. A passive infra-red motion analysis system is used to collect segmental kinematics, with GRF obtained using two strain gauge force plates. Residual errors are calculated at each sampled instant as the total external force on the body minus the sum of all segmental mass/acceleration products, expressed as percentages of body weight. Seventeen trials were collected on 5 normal males. The means RMS residual was 6.1 +/- 4.4% for the vertical axis, 3.1 +/- 1.3% for the anterior/posterior axis, and 3.0 +/- 4.8% for the medial/lateral axis. Masked by the RMS and ensemble averaging process, residuals in the vertical direction reached magnitudes as large as 43% of body weight near foot strike. These data suggest that our geometric model produced acceptable levels of "nonequilibrium," except at foot strike. Additional study will be made of the effect of kinematic data processing on the minimization of residuals.