Abstract
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.
Highlights
W HOLE body ground reaction forces (GRF) are used to evaluate gait kinetics and balance measures [1], [2]
If a simple inverted pendulum model of gait is assumed [3], the GRF is equal and opposite the sum of accelerations at the center of mass (CoM); and accelerations can be directly measured by Inertial Measurement Units (IMUs)
The main goal in this study is to evaluate the feasibility of estimating 3D GRF from a pelvis IMU, for different walking patterns seen in daily life for the complete gait
Summary
W HOLE body ground reaction forces (GRF) are used to evaluate gait kinetics and balance measures [1], [2]. GRF are measured using force plates installed under either the floor, or special treadmills. These, cannot be used in an ambulatory manner. If a simple inverted pendulum model of gait is assumed [3], the GRF is equal and opposite the sum of accelerations at the center of mass (CoM); and accelerations can be directly measured by Inertial Measurement Units (IMUs). Manuscript received November 4, 2019; revised February 10, 2020 and March 10, 2020; accepted March 29, 2020. Date of publication April 20, 2020; date of current version June 5, 2020.
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