In order to evaluate the occurring loads and the effectiveness, a measuring system is to be developed which allows a meaningful statement and a comparison between a static and a dynamic seat shell by measuring relevant parameters.
A belt force sensor was manufactured to determine the occurring tensile forces on the fixing belts of the seat shell during a dyskinetic extension movement. The belt force sensor was attached to the pelvic and foot fixation belts. The generated force within the belt is almost completely converted into the curvature of the aluminum brackets of the belt force sensor. This curvature of the aluminum brackets is detected by the elongation of the attached strain gauges and converted into a change in resistance that is directly proportional to the acting force. To measure the change in resistance of the strain gauges, the strain gauges are glued and wired into a Wheatstone full bridge on an aluminum bracket.
The tests with trial volunteers showed a significant reduction in the tensile forces in the dynamic seat shell compared to the static seat shell. The reduction is more than 50% in some trial volunteers. After conducting a significance test, the collected data could be described as being significant.
The methodology applied here provided reproducible and meaningful results on the applicability of the dynamic seat shell. The determined positive reduction of the forces in the dynamic seat shell must nevertheless be confirmed by further studies.