Sampling moiré method triaxial force plate with metal three-dimensionally printed structure

We report a triaxial force plate (FP) fabricated by a metal three-dimensional (3D) printer and sampling moiré (SM) method for displacement measurement. Ground reaction force (GRF) is an important index for foot biomechanics. For a detailed analysis of human locomotion, it is desired to examine the GRF distribution across the sole. FPs are widely used to measure GRF. Development of an FP array capable of multipoint measurement by miniaturizing each FP and arraying them is required. However, conventional FPs with built-in force sensor elements are difficult to array due to the proportional increase in wiring complexity with the number of FP elements. Another approach involves FPs that use mechanical components and external displacement meters, which can be arranged in an array, but this also leads to an increase in the number of displacement meters. Recently, we developed an optical FP capable of triaxial force measurements by capturing a two-dimensional grating attached to the mechanical component through a prism by a single camera and analysis with the SM method at a high resolution. This measurement method is applicable to multipoint simultaneous displacement measurements of an FP array owing to the extension of the camera’s field of view. On the other hand, from a mechanical perspective, it is desirable to manufacture the array structure as one batch. Here, we propose an FP mechanical component integrated with a plate and spring fabricated by a metal 3D printer. Experiments for measurement of spring constants were conducted, which showed a linear response to the applied force in each direction. Using the FP system with a prism and camera with the SM method, the proposed FP demonstrated the feasibility of triaxial force measurement. Therefore, the proposed FP could be applicable to the arraying of FPs.