Virtual Soldier Research (VSR) Program, Center for Computer-Aided Design (CCAD), College of Engineering, The University of Iowa, Iowa City, IA 52242, USA.
J Biomech. 2011 Feb 24;44(4):683-93. doi: 10.1016/j.jbiomech.2010.10.045. Epub 2010 Nov 19.
An optimization-based formulation and solution method are presented to predict asymmetric human gait for a large-scale skeletal model. Predictive dynamics approach is used in which both the joint angles and joint torques are treated as unknowns in the equations of motion. For the optimization formulation, the joint angle profiles are treated as the primary unknowns, and velocities and accelerations are calculated using them. In numerical implementation, the joint angle profiles are discretized using the B-spline interpolation. An algorithm is presented to inversely calculate the joint torques and the ground reaction forces. The sum of the joint-torques squared, called the dynamic effort, is minimized as the human performance measure. Constraints are imposed on the joint strengths (torques) and joint ranges of motion along with other physical constraints. The formulation is validated by simulating a symmetric gait and comparing the results with the experimental data. Then asymmetric gait motion is simulated, where the left and right step lengths are different. The kinematics and kinetics results from the simulation are presented and discussed. Predicted ground reaction forces are explained by using the inverted pendulum model. Predicted kinematics and kinetics have trends that are similar to those reported in the literature. Potential practical applications of the formulation and the solution approach are discussed.
提出了一种基于优化的公式和求解方法，用于预测大规模骨骼模型的不对称人体步态。预测动力学方法用于将关节角度和关节扭矩都视为运动方程中的未知数。对于优化公式，关节角度曲线被视为主要未知数，并使用它们计算速度和加速度。在数值实现中，关节角度曲线使用 B 样条插值进行离散化。提出了一种反算关节扭矩和地面反作用力的算法。关节扭矩平方和，称为动力努力，被最小化作为人体性能指标。在满足关节强度（扭矩）和关节运动范围以及其他物理约束的条件下施加约束。通过模拟对称步态并将结果与实验数据进行比较来验证公式。然后模拟不对称步态运动，其中左右步长不同。呈现并讨论了模拟的运动学和动力学结果。使用倒立摆模型解释预测的地面反作用力。预测的运动学和动力学具有与文献中报道的相似的趋势。讨论了公式和求解方法的潜在实际应用。
