INJURY CONTROL FOR WHEELCHAIR OCCUPANTS - Injury Biomechanics and Control: Optimal Protection from Impact - page 260

wheel forks [see National Science Foundation (NSF), 2001]. Therefore,
technologies that control the crash forces acting on both the wheelchair
rider and the wheelchair reduce the chance of injury. The movable plat-
form proposed in this chapter is intended to provide better control of these
crash forces.
To reduce the risk of injuries to wheelchair riders in a vehicle frontal
crash, it is proposed to attach the wheelchair to a movable platform rather
than to the vehicle body and to attach the wheelchair tiedown and the occu-
pant's restraint systems to the platform. Guides would allow the platform
to move within the vehicle. The motion of the wheelchair relative to the
vehicle that is necessary to reduce the forces transmitted to the wheelchair
in a crash is provided by the motion of the platform. An impact isolator can
be placed between the platform and the vehicle body, generating a force
interaction between these components. The isolator should be designed to
provide a substantial reduction in the loads transmitted to the wheelchair and
the occupant in a crash as compared with direct tiedown of the wheelchair
to the vehicle. At the same time, the displacement of the platform relative
to the vehicle body should be reasonably small to prevent the collision of
the wheelchair and the occupant with the vehicle's interior components and
other occupants.
This chapter describes a computer simulation of the behavior of the
occupied wheelchair tied down to the impact-isolated platform. Computer
models of powered surrogate and commercial wheelchairs (Shaw et al.,
1994; Kang and Pilkey, 1998; Bertocci et al., 1999; Bertocci, Hobson,
and Digges, 2000; Bertocci, Souza, and Szobota, 2003) have been used
for the investigation of the influence of wheelchair securement points
and wheelchair seat stiffness on the safety of the occupant as well as
for the evaluation of the effectiveness of wheelchair-integrated restraint
systems (Bertocci and Evans, 2000). The models were developed using
ATB/Dynaman software ( Dynaman User's Manual Version 3.0 , 1991). In
this chapter, a computer model of the same powered surrogate wheelchair
is developed using MADYMO software ( MADYMO Manuals , 2005). The
wheelchair is attached to the platform by a four-point strap-type tiedown
system. The occupant is restrained by an independent three-point belt
restraint. The upper end of the shoulder belt is anchored to a vertical
stanchion rigidly fixed to the platform and the lower end is attached to
the platform floor. Both ends of the lap belt are anchored to the platform
floor. Two types of controlled motion of the platform are considered, with
constant absolute acceleration beginning at the start of the crash pulse to
the vehicle and with constant absolute acceleration beginning at a time
before the crash. The latter case is associated with pre-acting control
discussed in Chapter 3 and requires that the crash instant and the crash
pulse shape be predicted ahead of time. The values of the acceleration of