Validation of a software-based stability assessment system for wheelchairs and their occupants

Injuries relating to unstable wheelchairs are frequent and can be serious. Current physical tilt testing methods for wheelchairs and their occupants present health and safety issues for both testers and wheelchair users. In this study, a comparison was made between a software-based wheelchair stability assessment technique and physical tilting of wheelchairs on an inclined ramp. One manual and one powered wheelchair were studied loaded with a Hybrid II anthropometric test dummy. The software system's performance was assessed for both ideal clinical use and domiciliary use where floors may not be perfectly level. Close correlation was shown between the two systems for both level and unlevel floors; Pearson correlation coefficient 0.75 - 0.97. Repeatability was demonstrated with a standard deviation range of 0.18 to 0.78. In the majority of cases, the software assessed stability angle was less than the recorded tipping angle, reflecting a factor of safety.