Modelling the propulsion characteristics of a standard wheelchair.

Recent wheelchair modelling work has focused on the efficiency of the human-racing wheelchair interaction. This paper builds on this work, investigating the development of a model appropriate for those using standard wheelchairs. A wheelchair racing model was initially used as the starting point for the generation of a number of model variations. Force predictions from these variations were compared to load cell data taken from an instrumented wheelchair during propulsion. Additional models where then developed, based on the characteristics of the models that performed best, and used to predict the forces in a second group of subjects. The analysis procedure was originally based on the calculation of a model index as a mathematical estimation of the theoretical closeness each model prediction had with the observed force. Visual comparisons of the force versus time were then incorporated into the procedure for evaluating the physical appearances of the profiles. The combination of the statistical and visual analysis led to selection of the final models for estimating the starting, constant, and stopping phases of wheelchair propulsion. The resulting models provide insight into the effects of a variety of factors on efficiency during propulsion in a standard chair.