Identification of the Mechanical Properties of Tires for Wheelchair Simulation

Abstract

The development of high performance wheelchairs and wheelchair simulators requires dynamic models taking into account the properties of tires. In this paper the properties of two wheelchair tires are measured by means of a rotating disc testing machine and are compared with the properties of bicycle tires, which have similar dimensions and structure. Tests are carried out considering variations in speed, inflation pressure and load. The possibility of fitting experimental results with the Magic Formula, the Dugoff formula and a linear model is discussed. A dynamic model of a wheelchair is developed, which includes a linear tire model derived from experimental results. Steady turning and slalom manoeuvres are simulated. Numerical results show the effect of tire properties on the handling characteristics of the wheelchair.

Contrary to basic kinematic modelling, during tight turns, wheelchairs can slide sideways by non-negligible magnitudes: Collision risks may be increased

“…The four qualitative statements cohere with both the following dynamical analysis and recent wheelchair tyre property investigations [8], [9], [10]. A preliminary observation for assisted wheelchairs is that all dynamic actions are handle forces.…”

“…It is therefore concluded that during push turns, lateral handle force and caster wheel motion resistance contributed to the resulting lateral drift away from curvature centre. Nevertheless, it is also reasonably concluded that the tyre property effects [8], [9] and [10] present for pull turns, were present for push turns. Push and pull turn lateral drift magnitudes therefore differed.…”

“…While the lateral drift results do not permit the relationship with tyre parameters to be determined some agreements and contrasts with [8], [10] are possible. For co-rolling turns, Figure-graphics of simulations indicate that, decreasing tyre stiffness [8], [10] decreases path curvature. This would suggest that different tyres might reduce lateral drift.…”

“…So lateral drift away from curvature centre cannot be a result of lateral handle force or caster wheel motion resistance. Given that, [8], [9], [10] have demonstrated that wheelchair simulations with different tyre parameters results in different wheelchair path curvatures, it is reasonably concluded that during pull turns, tyre properties play a critical part in lateral drift away from curvature centre.…”

“…The following recent evidence suggests that lateral drift occurs. Wheelchair lateral dynamics investigations, [8], [9], [10] have demonstrated that for the same dynamic input, wheelchair simulations with different tyre parameters required different lateral spaces to turn. Therefore, wheelchair lateral kinematics are more complex than the basic kinematic description.…”