Determination of wheelchair dynamic load data for use with finite element analysis

A methodology is introduced for the experimental determination of the dynamic loads which act on a wheelchair. A box frame wheelchair and a cantilever frame wheelchair were tested on an ANSI/RESNA curb-drop tester [1]. The accelerations of an ANSI/RESNA test dummy [1] were recorded with an array of 12 accelerometers mounted as four three-axis groups. Signal averaging was used to produce a composite dynamic load history. The dynamic loads were calculated from the acceleration data and the inertia of the test dummy using software written by the authors. These loads were imported into a finite element program (ALGOR) [5], [6] as load cases. A prototype carbon fiber design was then optimized through design and analysis iterations. The results of the acceleration data indicate that the curb-drop test produces an asymmetric loading scheme. One of the rear wheels hits the ground before the other, placing most of the dynamic load on one side of the wheelchair. The favored side appears to be fixed at the time of setup. Preliminary results are given for the design of a modular carbon fiber wheelchair using the finite element (FE) method. These results indicate, however, that the use of a static factor of safety is, in most cases, inadequate for the dynamic loads present in the curb-drop test.