Analysis of backward falls caused by accelerated floor movements using a dummy.

This investigation used a standing dummy on slippery and non-slippery surfaces with accelerated movements of a floor to simulate falling backward events. The results revealed the duration of falling, head impact velocity, etc., which are valuable for guiding the development of personal protective equipment, such as wearable airbags. The mechanism, by which a dummy falls backwards due to abrupt accelerated movements of a floor, was studied. A small linear accelerator was designed to apply a series of 20 combinations of step-shaped accelerations of varying durations to cause a standing dummy to fall backwards. Two flooring surfaces, namely, a smoothed aluminum surface sprayed with mould lubricant and a surface with abrasive materials, were used. Ankle, knee and hip joints of the dummy were adjusted in fixed or unfixed positions. When the dummy fell backwards like a rigid body, the head impact velocities were almost constant at around 22 to 23 km/h, and the mean duration of falling to the ground was 0.83 s, when standing on a slippery surface, and 0.98 s when standing on a non-slippery surface. The duration of falling to the ground tended to converge at 0.8 s as the maximum velocity of accelerated movements of the floor increased, irrespective of the frictional properties of the flooring surfaces.