RESNA 26th International Annual Confence

Technology & Disability: Research, Design, Practice & Policy

June 19 to June 23, 2003
Atlanta, Georgia

EFFECT OF UNIVERSAL DOCKING INTERFACE GEOMETRY (UDIG) PLACEMENT ON WHEELCHAIR AND OCCUPANT KINEMATICS

Linda van Roosmalen, PhD; Sean A. Reeves, BS; Douglas A. Hobson, PhD
Department of Rehabilitation Science and Technology,
Injury Risk Assessment and Prevention Laboratory,
University of Pittsburgh, Pittsburgh, PA, USA

ABSTRACT

A Universal Docking Interface Geometry (UDIG) has been under development to enable independent wheelchair securement (docking) for all WMD users traveling in motor vehicles [1]. Wheelchair and occupant kinematics during frontal (30mph/20g) and side (15mph/12g) impact were investigated for various attachment locations of the UDIG. Computer simulations were conducted with a manual wheelchair model and a 50th percentile Anthropomorphic Test Dummy (ATD). Wheelchair center of gravity (CG) and UDIG placement were systematically altered and their effect on horizontal (fore/aft), vertical and lateral displacement of the wheelchair (at the P-point) and occupant (head and knee) were measured. Simulation results show that occupant and wheelchair excursions stayed well within ISO excursion limits. Excursions were minimized when the UDIG was mounted wide and forward on a low-CG wheelchair, and when the UDIG was grasped high.

BACKGROUND

Figure 1 (left): Rear view of proposed UDIG geometry and clearance zone (mm).

Wheelchair securement is a safety concern for individuals using WMDs when traveling in motor vehicles. WMDs include manual and power wheelchairs, scooters, and specialized seating bases (e.g. tilt-in-space seating system). Currently, the four-point strap type tie-down systems are commonly used, because they fit a wide range of WMDs. However, four point tiedowns can be difficult to use and very time consuming, especially when used in public transportation with drivers that may not be familiar with the securement system or the WMD being secured [2]. Automated docking has been proposed to enable individuals to independently secure their WMDs [3]. Docking type securement devices can be permanently mounted to the vehicle floor and engage with a compatible adapter that is attached to the rear of a WMD. The agreement on a geometry of the compatible adapter or UDIG (see figure 1) is key to the success of automated docking [1]. The objective of this study was to determine the impact of UDIG placement on ISO-10542 requirements for wheelchair and occupant excursions [4].

Figure 2(right): Simulation model of a manual wheelchair with P-point and UDIG.

RESEARCH METHOD

Computer simulations were conducted using Dynaman version 4.0 and a validated model of a standard manual wheelchair (46 lb.). A 50th percentile male Hybrid III ATD was used to represent the wheelchair occupant [5]. The occupant was restrained with a wheelchair mounted pelvic belt and a vehicle mounted shoulder belt. Figure 2 shows the wheelchair model and figure 3 the ranges of location of the UDIG adaptor, i.e. fore/aft position, height position (w.r.t. the floor of the vehicle), and width along the centerline.

Figure 3: Diagram of UDIG placement on a manual wheelchair in fore/aft, high/low and wide/narrow position

Frontal impact was simulated using a 30mph/20g, and side impact was simulated using a 15mph/12g sled pulse [6, 7]. Since wheelchair CG can affect wheelchair and occupant kinematics, the CG was systematically altered from a 12 in. (low) to 17.5 in. (high) above the vehicle floor for the various simulation trials [8, 9]. The variables measured were horizontal (X) displacement, vertical (Z) displacement, and lateral (Y) displacement of the ATD's head, knee and wheelchair P-point (see Figure 2). Lateral displacement of the wheelchair (@ the P-point) was measured during side impact trials only. Excursion measurements during frontal impact were recorded during forward motion only.

RESULTS

Simulation results of wheelchair and occupant forward (X-dir) and vertical (Z-dir) excursions due to frontal impact for the various UDIG locations are listed in Table 1. Table 1 also lists the excursion limits from ISO-10542 for wheelchair, head and knee for frontal impact. Simulation results of lateral (Y-dir) and vertical (Z-dir) excursions due to side impact are listed in Table 2. Excursion limits for side impact are yet not available in current wheelchair standards.

1. Van Roosmalen, L. and D.A. Hobson. Issues related to the location of a universal interface for automated wheelchair securement. RESNA annual conference. 2002. Minneapolis, MN: RESNA Press.
2. Hardin, J.A., C.C. Foreman, and L. Callejas, Synthesis of securement device options and strategies. 2002, National Center for Transit Research (NCTR): Tampa. p. 74.
3. Hunter-Jaworski, K., The development of an independent locking securement system for mobility aids on public transportation vehicles: Volume 2. 1992, NTIS.
4. ISO, ISO/DIS 10542 Wheelchair Tiedowns and Occupant Restraints Systems - Part 1: General Requirements. 1999, ISO.
5. 5. Leary, A. and G. Bertocci. Design criteria for manual wheelchairs used as motor vehicle seats using computer simulation. in RESNA Annual Conference. 2001. Reno, NV.
6. NHTSA, D., Y.C., Design considerations for occupant protection in side impact- a modeling approach. 1988, NTHSA, Department of Transportation: Washington, DC.
7. NHTSA, F., E., Interaction of car passengers in side collisions- tests with four new side impact dummies. 1983, NTHSA, Department of Transportation: Washington, DC.
8. Bertocci, G.E., T.E. Karg, and D.A. Hobson, Wheelchair classification system and database report. 1996, University of Pittsburgh: Pittsburgh, PA.
9. Bertocci, G.E., K. Digges, and D. Hobson. The affects of wheelchair securement point location on occupant injury risk. in The Annual RESNA Conference. 1997: RESNA Press.