Three-Axis Force Plate Using High-Speed Line-Scan Camera and Tilted Pattern for Sampling Moiré Method

Abstract

Force plates utilizing various principles capable of simultaneously measuring vertical and shear forces have been developed to analyze ground reaction force (GRF) in studies of animal locomotion mechanics. Recently, a triaxial force plate with high accuracy and measurement independence has been proposed using the sampling moiré (SM) method and a prism. The SM method can detect in-plane displacement of a pattern image with significantly higher accuracy than pixel size. However, with implementations using area-scan cameras, it was difficult to achieve both large number of pixels, which determine force resolution, and high frame rate, which affects temporal resolution. Here, we propose an SM method force plate with high accuracy and time resolution using a line-scan camera with a single vertical pixel, high horizontal resolution, and high frame rate. To realize three-axis force measurement from 1-D images, a pair of tilted patterns are utilized for SM method analysis. The fabricated force plate was calibrated and confirmed to have a force resolution of less than 35 mN for each axis and a positional error of less than 3%. Therefore, the proposed force plate can be useful for highly accurate GRF measurement with high frame rate capabilities.