Pelvic Restraint Fit

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• Snugly over the bony parts and across front of pelvis
• ‘Belt junction’ near the hip
• Not across abdominal area
• Not over the wheelchair arm rests
• No twisted belt assembly

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Pictures showing the recommended optimal angles and zones for the pelvic restraint.

Occupant Restraint Safety

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• Improperly positioned pelvic belt:
  • Abdominal injury due to ‘submarining’
  • Lumbar vertebra injury in frontal crashes
• Improperly positioned shoulder belt:
  • Excessive head excursions
  • Secondary impact with vehicle surfaces
  • Injuries to vital thoracic cavity organs

Occupant Restraint

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• Use both pelvic and shoulder belt to restrain the occupant
• Lead restraints over bony anatomy
  • Shoulder restraint over the Sternum
  • Pelvic restraint over the (pelvis) Iliac Crests
• Avoid loading soft tissues (abdomen)
• Remove belt slack
• Use a retractor to reduce upper torso belt slack
• Restraint pre-tensioner reduces belt loading

Common Problems

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• Shoulder belt slip off user’s shoulder
  • Due to shallow angle of torso belt
• Shoulder belt rubs against user’s neck
  • Discomfort,
  • Resistance to using belt
  • Decreased upper torso restraint
• Anchoring upper torso restraint below shoulder may result in downward loading of torso and spine.

The Real World

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4-Point Tiedown Systems

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Occupant Restraints & Postural Supports

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Possible Solution

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• Automated Wheelchair Securement
  • Universal docking approach
• Seat Integrated Occupant Restraint System
  • Customized upper torso and pelvic restraint

Docking Interface

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Pictures showing the comparison between a car trailer-hitch and a wheelchair docking interface.

Effect of UDIG location on Wheelchair and Occupant Kinematics

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• Securement point location on WC
  • Rear tie-down close to WC center of gravity
  • Location too low: forward wheelchair and occupant rotation during frontal impact
  • Location too high: rearward wheelchair rotation during frontal impact

Numerous Wheelchair Designs

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Pictures showing various types of wheelchairs, with all their differences and difficulties of attaching a UDIG to.

Only 1 interface geometry

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• Need for standardization
  • ISO 10542-3 (docking type securement)
  • Use with all wheelchair types
  • Use with multiple docking stations
• Universal Docking Interface Geometry requirements:
  • Specific dimensions
  • Clear zones

Specifications for vertical and horizontal location of a UDIG adaptor on the rear of a wheelchair

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Graphic of technical engineering drawing of the front and side view of the geometries of a wheelchair interface needed for automated wheelchair securement.

Specification of clear zones that allow access to the UDIG adaptor (max width)

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Graphic of technical engineering drawing of the front and side view of the geometries of a wheelchair interface needed for automated wheelchair securement.

Docking System Technology

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• Ongoing research at the University of Pittsburgh’s RERC on Wheelchair Transportation Safety
• Standards development

Wheelchair Mounted Restraint

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• Improved occupant restraint
• Customized restraint
• Ease of use
• Increased wheelchair strength
• Added wheelchair weight

Feasibility

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Picture that shows a 50th percentile male dummy in a wheelchair setup. The dummy is restrained by a wheelchair mounted (integrated) occupant restraint system.

Comparison Study

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Graphic comparison between a vehicle mounted and a wheelchair integrated occupant restraint system.

Wheelchair Mounted Restraint

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• Ongoing research at the University of Pittsburgh’s RERC on Wheelchair Transportation Safety

Caster Crashworthiness

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• Failure of caster assemblies was observed during sled impact testing (20g/30mph)
  • Light weight manual wheelchairs
  • Heavier power-chairs
• Uncontrolled caster/fork failure may result in:
  • Abrupt high chest loading
  • Excessive forward movement
  • Submarining risk when using vehicle mtd. occupant restraints

Caster-Fork Assembly Loads

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• Affected by:
  • Occupant weight
  • Wheelchair design (Power/Manual)
  • Seating system crashworthiness
  • Wheelchair securement location (high/low)
  • Occupant restraint scenario (vehicle vs. wheelchair mounted pelvic/shoulder belt)

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Pictures showing various caster wheels and caster forks.

Test Setup

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• Sledpulse: 20g/30mph
• 50th percentile male Hybrid III ATD
• Surrogate wheelchair base
• Vehicle mounted occupant restraint system
• Varying seat and back surfaces
• Varying wheelchair securement point location

Test Setup: Caster Load Cells

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Pictures showing the sled test platform with integrated load sensing plates to record caster wheel loading during frontal impact.

Caster Load Direction

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Picture showing the caster loading during frontal impact.

Peak Loads

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Table that shows the various wheelchair and seating system setups, failures, and recorded normal and shear loads from the load sensor.

Pendulum Impact Tester (PIT)

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• Development of a dynamic test to determine:
• Caster failure
• Caster loading
• Caster deformation
• Energy absorption

Conclusions

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• Results from PIT resembles dynamic impact test data
• Similar load patterns
• More caster and fork testing ongoing for validation test method

In addition:

• Computer simulation used to develop crashworthy casters

Wheelchair Crashworthiness

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Wheelchairs are designed to provide mobility to individuals and not designed as automobile seats,so, in many cases, the level of protection that wheelchair and its seating systems can provide under impact is unknown.

WCSSs are often provided as add on or replacement products after the wheelchair has been in the field, so they will not be sled tested by the ANSI/RESNA WC/19 standard.Therefore, as part of wheelchair transportation safety researches, crashworthiness of wheelchair seating systems have been also evaluated.

Wheelchair Seating System (WCSS) Crashworthiness

WCSS Static Tests – Applied Forces

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The forces applied to the seating systems in static test were determined using computer simulation and mathematical calculation.