Contrary to basic kinematic modelling, during tight turns, wheelchairs can slide sideways by non-negligible...

Small spaces make collision-free turns difficult for wheelchair users. Contrary to basic kinematic wheelchair modelling and not considered previously by engineers; when wheelchairs turn in small spaces, could lateral drift (sideways slipping) increase the risk of collisions with surrounding structures such as walls and doorways? An improved kinematic understanding can inform building design and therapeutic involvement with wheelchair use. Wheelchair lateral drift is investigated. Two experiments with assisted wheelchair use are reported. Weights represented wheelchair occupants. First, lateral drift was measured by motion capture (VICON): turns (n = 225) made by the experimenter, for six radii of curvature (0-613 mm) and four total-masses (81-142 kg). Second, lateral drift was measured by ruler: turns (n = 105) made by experienced wheelchair assistants (n = 22), for three radii of curvature (0, 306, and 800 mm), and self-selected maximum comfortable weights. Lateral drift away from centre of curvature occurred for all radii of curvature greater than 0 mm, and a maximum median lateral drift of 27 mm/rad occurred for 142 kg total mass with 459 mm radius of curvature. Lateral drift increased with mass (r² = 0.68 for 358 mm radius of curvature). During tight turns, lateral drift magnitude and direction is such that it can increase risks of collisions with surrounding structures.