基于PCA-WNN预测跑步中垂直地面反作用力的研究
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1.北京体育大学 运动人体科学学院;2.国家体育总局 体育科学研究所

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Predicting Vertical Ground Reaction Force during Running on Treadmill Using Principal Component Analysis and Wavelet Neural Network
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    摘要:

    目的 建立基于主成分分析(Principal Component Analysis, PCA)和小波神经网络(Wavelet Neural Network, WNN)模型预测跑台上人体所受垂直地面反作用力(vertical Ground Reaction Force, vGRF)的方法。方法 选取9名后足着地者在跑台上以12、14与16 km/h速度跑步30 s,采集下肢环节质心速度和关节角度等运动学数据与vGRF值。随机选1名受试者42个单步为测试样本,其余8人共273个单步为训练样本。构建神经网络框架,激活函数为Morlet小波基函数;PCA累积贡献率为95%的17个主成分,与力值一起输入到WNN。以均方根误差(RMSE)、标准均方根误差(NRMSE)与相关系数(r)等指标评估模型性能。结果 本研究预测曲线具有良好拟合度;预测与测量值间误差较小(RMSE=0.18-0.28 BW, NRMSE=6.2-8.42%),两者有很高相关性(r > 0.97, P<0.01);预测的冲击力和推进力峰值与测量峰值间误差较小且相对稳定(RMSE=0.08-0.37 BW, NRMSE=2.91-11.14%),尤其12 km/h预测结果最好。结论 本研究构建的PCA-WNN模型可准确、稳定预测出跑台上跑步时人体所受垂直地面反作用力,为在跑台上获得动力学数据和实时监测提供新途径。

    Abstract:

    Objective To explore the accuracy and stability of principal component analysis and wavelet neural network model to predict the vertical ground reaction force on a treadmill. Methods Nine rearfoot strikers were selected and participated in a running experiment on an instrumented treadmill (Germany, h/p/cosmos mercury) at 12, 14 and 16 km/h. The treadmill has a running area of 150 50 cm and two force plates of Kistler. And the kinematics data and vGRF values, such as the center of mass velocity, joint angle and angular velocity of the lower limbs, were collected. The 273 samples of training set and 42 samples of test set were input into the PCA-WNN model. A three-layer neural network framework is constructed by python 3.8, in which the activation function of the hidden layers is the Morlet function, and the loss function E is optimized by the gradient descent method. The cumulative contribution rate of principal component analysis is set to 95%, and the kinematic data is filtered out and input into the WNN model for training and predicting. The performance of the model is evaluated by the root mean square error, standard root mean square error, mean absolute error, maximum error and correlation coefficients. Results 17 principal components such as velocities of the center of mass of segments and joint angles were input into the wavelet neural network model. On the whole, the vertical ground reaction force curves predicted by the model has a good fit with the measured curve, the error is quite small (RMSE=0.18-0.28 BW,NRMSE=6.2-8.42%) and there is a significant correlation between the two (r> 0.97, P<0.01) ; the errors between the predicted and measured impact force peak and active force peak are all quite small and relatively stable (RMSE=0.08-0.37 BW,NRMSE=2.91-11.14%). In particular, the prediction result of 12 km/h is more similar to the measurement and there is no significant difference(P>0.05). Conclusion The principal component analysis and wavelet neural network model constructed in this study can accurately and stably predict the vertical ground reaction force during running on a treadmill, which provides a new method to obtain kinetic data and to perform real-time monitoring on a treadmill.

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  • 收稿日期:2021-07-21
  • 最后修改日期:2021-09-06
  • 录用日期:2021-09-07
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