COMPARISON OF A MODIFIED HYBRID III ATD TO A HUMAN TEST PILOT DURING POWER WHEELCHAIR DRIVING

It is estimated that there are 85,000 serious wheelchair accidents annually, of which 80% are attributable to tips and falls. Despite the increasing trend in wheelchair accidents every year, there is little literature on the cause and prevention of these accidents. Test dummies provide an ethical and practical alternative to subjects when assessing the risks and prevention mechanisms of tips and falls in controlled studies. However, design criteria for anthropomorphic test devices (ATDs) were based on the response and tolerance data acquired from cadaver studies and human volunteers. Such cadavers are typically of advanced age, and have anthropometrics reflecting a healthy, unimpaired population. For that reason, use of ATDs in relatively low speed wheelchair studies may under estimate the risk of injury.The purpose of this study was to develop and validate a low speed, low impact test dummy for use in the study of the prevention of tips and falls from wheelchairs. A kinematic analysis comparing the trunk bending of a Hybrid III test dummy (HTD) to that of a wheelchair user during various braking trials served for validation. In addition, a dynamic model was used to determine underlying causes of the motion. Statistical differences were not found (p>.05) in the peak trunk angular range of motion, velocity, and acceleration measures of a modified HTD over a range of wheelchair speeds and decelerations. This is promising evidence that the test dummy is a suitable surrogate for a wheelchair user in low speed dynamic studies. However, the HTD underestimated the motion of a wheelchair test pilot during the fast speed and power-off braking condition.A dynamic model consisting of a cart with an inverted pendulum was used to provide additional insight into the differences in motion. Although the model produced consistent values for damping and stiffness coefficients, evidence indicates that the functional form of the model may be incorrect. The model likely estimated properties for a wheelchair/rider system rather than only the rider. Further analysis showed an impingement occurring between the pelvis and thighs of the HTD. Removing the impingement will further increase the similarities between the HTD and test pilot