Force Plate with Non-direction Displacement Sensors and Springs

Abstract

The ground reaction force (GRF) is one of the important factors in clarifying human movement, and a force plate is widely used for measuring GRF. This paper describes the force plate with seven springs and four non-contact displacement sensors. The proposed measurement principle allows for easy changes in shape and physical properties. When the GRF is applied to the force plate, the GRF is evaluated from the vertical and horizontal displacement of the top surface plate. The non-contact displacement sensors are composed of the magnet and planar coil. The force plate’s resonant frequency was 133 Hz. The calibration experiments show that vertical and horizontal forces and moments could be measured independently. The positional error of vertical force was 5% to −5%, and the resolutions were 1.95 N and 2.06 N in the anterior-posterior and vertical directions, respectively. Furthermore, the GRF waveform characteristics measured with a force plate were similar to the waveform of a normal gait.