Ground Reaction Forces (GRF) during gait are measured using expensive laboratory setups such as in-floor or treadmill force plates. Ambulatory measurement of GRF using wearables enables remote monitoring of gait and balance. Here, we propose using an Inertial Measurement Unit (IMU) mounted on the pelvis to estimate the GRF during gait in daily life. Calibration procedures and an Error State Extended Kalman filter (EEKF) were used to transform the accelerations at the center of mass (CoM) to the 3D GRF. The instantaneous 3D GRF was estimated for different overground walking patterns and compared with the 3D GRF measured using the reference ForceShoe™ system. Furthermore, we introduce a changing reference frame called the current step frame that followed the direction of each step made. The frame was defined using movement of the feet, and the estimated GRF were expressed in this new frame. This allowed direct comparison and validation with the reference. The mean and standard deviation of error between the estimated instantaneous 3D GRF and the reference, normalized against the range of the reference, was 12.1 ± 3.3% across all walking tasks, in the horizontal plane. The error margins show that a single pelvis IMU could be a minimal and ambulatory sensing alternative for estimating the instantaneous 3D components of GRF during overground gait.

中文翻译：

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便携式步态实验室：在脚IMU定义的帧中使用骨盆IMU估算3D GRF

步态期间的地面反作用力（GRF）使用昂贵的实验室设置（例如地板或跑步机测力板）进行测量。使用可穿戴设备动态测量GRF可以远程监视步态和平衡。在这里，我们建议使用安装在骨盆上的惯性测量单元（IMU）来估算日常生活中步态时的GRF。使用校准程序和错误状态扩展卡尔曼滤波器（EEKF）将质心（CoM）的加速度转换为3D GRF。估算了不同地面行走模式的瞬时3D GRF，并将其与使用参考ForceShoe™系统测得的3D GRF进行了比较。此外，我们引入了一个变化的参考框架，称为当前步骤框架，它遵循每个步骤的方向。框架是通过脚的移动来定义的，并在此新框架中表示估算的GRF。这样可以直接与参考进行比较和验证。相对于参考范围归一化，估计的瞬时3D GRF与参考之间的平均误差和标准差在水平面上的所有行走任务中为12.1±3.3％。误差幅度表明，单个骨盆IMU可能是一种最小且可动态感应的替代方案，用于估算地面步态期间GRF的瞬时3D分量。