一种用于OpenSim的非线性缩放方法

A Nonlinear Scale Method for OpenSim

目的提高OpenSim生物力学模型静态与动态配准精度,进而提高运动学和动力学参数计算的可靠性。方法通过位姿调整、构建插值函数,实现基于运动学实验数据的模型非线性缩放。使用两组公开实验数据(GC3和GC5)进行建模分析,计算模型肢段长度和关节作用力,并与解剖标记点缩放方法(anatomical landmark scale,ALS)和线性缩放方法的计算结果及实际测量值比对,验证方法的有效性。结果缩放所得模型的肢段长度与实际测量值的最大偏差14.74 mm,在文献给定范围(4.0±13.8)mm内;缩放和逆运动学计算的标记点误差满足OpenSim给定要求;计算所得关节接触力均方根误差(GC3:0.40 BW,GC5:0.34 BW)较ALS方法(GC3:0.64 BW)和OpenSim线性缩放方法(GC5:0.40 BW)小;蒙特卡洛分析结果同时表明,对于模型标记点初始位置的变化,该方法计算关节接触力误差范围更小,肢段长度波动小于5%。结论该非线性缩放方法可行,且在目前验证条件下可以提高OpenSim运动学和动力学建模效率及仿真分析结果的精度。

Objective To improve the static and dynamic matching precision of OpenSim biomechanical models,and further improve the reliability for calculation of kinematic and kinetic parameters.Methods Model nonlinear scale based on kinematic experimental data was implemented by position adjustment,interpolation function calculation.For the verification of this method,two open dataset(GC3 and GC5)were used to build the nonlinear scaled models and calculate the limb lengths and joint reaction forces.The results were compared with those calculated by anatomical landmark scale(ALS)and linear scale method.Results The maximum discrepancies between limb length of nonlinear scaled model and actual model were 14.74 mm,which were in the range(4.0±13.8)mm reported by other literature.Marker errors of scale and inverse kinematic calculation could fulfill the requirement of OpenSim.As for calculated joint reaction forces,the root mean square errors(RMSEs)(GC3:0.40 BW,GC5:0.34 BW)were smaller than those of anatomical landmark scale(ALS)(GC3:0.64 BW)and OpenSim linear scale method(GC5:0.40 BW).Besides,the results of Monte Carlo analysis indicated that,with the variation of initial positions of model markers,the range of joint reaction forces errors was smaller and limb lengths fluctuated within 5%.Conclusions The nonlinear scale method in this study is effective,and it can improve the efficiency of kinematic and kinetic modeling process and raise the precision of simulation results under current verification condition.