GB/T 18029.1-2024 Wheelchairs - Part 1: Determination of static stability
1 Scope
This document specifies test methods for determining the static stability of wheelchairs.
It is applicable to manual and electrically powered wheelchairs, including scooters, with a maximum speed not greater than 15 km/h, intended to provide indoor and/or outdoor mobility for one disabled person whose mass is within the range represented by ISO 7176-11.
For active stability-controlled wheelchairs, this document applies to the device in a stable, parked state.
This document provides a method for the measurement of the tipping angles (either wheelchair tipping angle or anti-tip device tipping angle), but this method is not applicable to wheelchairs with lateral anti-tip devices and does not consider sliding on the ground.
This document also includes requirements for test reports and information disclosure.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 7176-11 Wheelchairs - Part 11: Test dummies
Note: GB/Z 18029.11-2021, Wheelchairs - art 11: Test dummies (ISO 7176-11:2012, IDT)
ISO 7176-15 Wheelchairs - Part 15: Requirements for information disclosure, documentation and labelling
Note: GB/T 18029.15-2008, Wheelchairs - Part 15: Requirement for information disclosure,documentation and labelling (ISO 7176-15:1996, IDT)
ISO 7176-22 Wheelchairs - Part 22: Set-up procedures
ISO 7176-26 Wheelchairs - Part 26: Vocabulary
Note: GB/T 18029.26-2014, Wheelchairs - Part 26: Vocabulary ((ISO 7176-26:2007, IDT)
3 Terms and definitions
For the purposes of this document, the terms and definitions in ISO 7176-26 and the following apply.
3.1
active stability-controlled wheelchair
wheelchair that actively controls or enhances its stability (by electronic or other means) when static and/or when in motion
3.2
anti-tip device
device which limits the extent of tipping of a wheelchair
Note: Anti-tip devices can operate in forward, rearward, or lateral directions. Some anti-tip devices have a spring suspension. Some running wheels can act as anti-tip devices, but their primary function is to be running wheels. Foot supports can serve as anti-tip devices if the manufacturer designates that they are intended to serve in that capacity. A change in the wheelchair configuration or control characteristics to enhance stability is not considered an anti-tip device.
3.3
anti-tip device tipping angle
angle of the test platform from the horizontal at which the wheelchair starts to tip about the anti-tip device
3.4
contact point
midpoint of the region of contact between a wheel or other part of the wheelchair and the ground
Note: In the test procedures specified in this document, the ground can be the test platform or its covering that lies between the test platform and the wheel or the post.
3.5
force detection point
point at which the force under an uphill wheel is monitored
Note: This can be determined as the point at which a sheet of paper will slide between the wheel and the contact surface.
3.6
lockable wheel
wheel equipped with parking brake, or wheel whose rolling motion is prevented by the means of propulsion (e.g. by hands, levers, motors)
3.7
non-lockable wheel
wheel that is not a lockable wheel
3.8
parked state
static position that will allow the occupant to transfer into or out of the seat
3.9
running wheel
wheel that normally runs on the surface while the wheelchair is travelling at a constant speed on a level surface
3.10
wheelchair tipping angle
angle of the test platform from the horizontal at which the vertical projection of the centre of mass moves outside of a polygon connecting the contact points of all the running wheels (to be assessed by empirical measure)
Note 1: The instant at which the wheelchair starts to tip is reached when the forces become zero under all uphill running wheels (i.e. one edge of the polygon lies directly below the centre of mass).
Note 2: A number of methods are available with which to determine when the forces become zero under the uphill wheels. These include, but are not limited to, the following: the ability to pull pieces of paper from beneath the wheels, visual identification of when the wheels lift from the test platform, or the use of force-sensing instrumentation.
4 Principles
4.1 Static stability
Theoretically, a loaded wheelchair is statically stable as long as the gravity force line from the centre of mass is inside the area on the ground that is confined by the outline of the contact points (see 3.4) of its wheels. Wheelchair stability increases as the angle between a vertical plane through the axis of tip and a plane that contains the centre of mass and the axis of tip increases. A wheelchair will tip when it is tilted beyond this measured angle (see Figure 1) about the axis of tip. The wheelchairs can either tip about the contact point when the wheels are locked or about the wheel axle when the wheels are unlocked (see Figure 1).
Since the location of the centre of mass is not known, it is not possible to measure the tipping angle directly. Therefore it is determined with the wheelchair on an adjustable slope test platform. The angle of the slope on which the wheelchair starts to tip is measured. The angle of the test platform represents the tipping angle.
