Force Plate with Simple Mechanical Springs and Separated Noncontact Sensor Elements

Abstract

This paper reports on a force plate (FP) using mechanical springs and noncontact distance sensors. The ground reaction force (GRF) is one of the factors for clarify biomechanics, and FPs are widely used to measure it. The sensor elements of conventional FPs are mainly strain gauges. Thus, the mechanical properties of FP depend on the sensor element performance. If the FP performance must change, we must redesign the FP, including changing the sensor elements. Here, we proposed an FP that uses a measuring principle based on simple springs and noncontact sensors. The shape and performance of the proposed FP are expected to change easily. As a prototype device, we designed and fabricated an FP installed with 12 springs and four sensors for human walking. A planar coil and magnet were used as the sensor elements, and the sensor output was proportional to the vertical and horizontal displacements. The FP resonance frequency was 123 Hz, which was larger than the required specification. The calibration experiments showed that vertical and horizontal forces and moments could be measured independently. The FP’s resolutions were 1.9 N and 1.4 N in the anterior–posterior and vertical directions, respectively. Furthermore, the fabricated FP measured GRF similarly to the commercial FP when a human walked on the plate. These results suggest that the proposed method will be helpful for FPs with custom-made requirements.

Measurement method of a microspring-supported force plate with an external laser displacement meter

“…For example, instead of a 3D printer, a MEMS structure can be constructed with a mechanical plate and supporting springs. Eddy current displacement meters are also applicable as sensing elements [26]. Additionally, capacitive sensors with a sub-nm resolution will lead to more sensitive measurements [27].…”

“…It should be mentioned that a 3D printer can only produce a mechanical structure, however, a force sensor can be constructed by placing the sensor elements separately. Recently, a biaxial force plate for humans has been developed with a mechanical structure and noncontact type sensors [26]. A small cantilever structure with a laser displacement meter has also been used for the GAF measurement of an insect [12].…”

Novel 3D Force Sensors for a Cost-Effective 3D Force Plate for Biomechanical Analysis

“…Indeed, many smaller research and sports programs are inhibited from purchasing a single 3D force plate and may opt for a cheaper unidimensional or two-dimensional force plate, which lacks critical information needed for many biomechanical analyses. As Sensors 2023, 23, 4437 2 of 9 a response to this lack of affordability for high-quality force plates, several researchers have set out to design, construct, and test force plate systems that can be replicated at much lower costs [8][9][10][11][12]. However, of these recent attempts, only two experimental force plates measured forces in three dimensions, and both were limited to low force capacities, inhibiting use for sports performance [8,9].…”