Characteristics of factors affecting axle load and friction forces in a wheelchair.

Abstract

Purpose: The aim of the presented research was to determine the impact of the position of the centre of gravity of the human-wheelchair system on the load on its axles.

Materials and methods: Experiments concerned measurements of the centre of gravity position and parameters related to wheelchair dynamics. This allowed for the determination of: the forces loading the wheelchair axles, the values of friction forces for individual wheels, and the demand for driving torque.

Results: Change in the average velocity of the wheelchair (0.24 m/s, 0.31 m/s, 0.36 m/s) does not cause significant changes in the position of the centre of gravity. An increase in the inclination of the wheelchair (from 0° to 7°) causes changes: a decrease in the load on the front axle, on average: 63.1 N, an increase in the load on the rear axle, on average: 65.3 N, the position of the centre of gravity: 54.2 mm. In turn, for an increase in the angle of inclination (from 7° to 14°), it causes, respectively: an average decrease of 114.9 N, an average increase of 116.5, and a change of position of 96.7 mm.

Conclusions: Changing the position of the centre of gravity significantly alters the load distribution on the front and rear axles of the wheelchair. This changes the values of friction forces, which affects the demand for driving torque. Taking into account variating acceleration additionally increases the resistance forces and the range of their variability.