How It Works...ue No.45

TRANSPORT

“Large tracked wheels, reinforced pivot frames and high-torque motors allow for cross-country use”

Electric wheelchairs How do these modern mobility vehicles get people from A to B? Cutting-edge mobility Discover the technology packed into one of today’s state-of-the-art electric wheelchairs

Control panel

Seat

An armrest-mounted controller allows adjustment of the chair’s speed and seat orientations, as well as access to diagnostics.

The chair’s seat is elevated from the systems platform on a movable centre post. It can be adjusted on a variety of planes.

068 | How It Works

The chair’s control panel and motor are connected to the battery station via a cabling system installed with a circuit breaker.

Joystick The chair’s speed and directional movement are controlled with a joystick; this can be fixed on either arm.

Pivot frame Forward and rear directional wheels are supported by pivot frames. These connect the wheels to the platform and ensure a longer wheelbase.

Where did wheelchairs originate? While wheeled platforms are recorded dating back to the 6th century BCE, one of the earliest references to wheelchairs being used in their modern incarnation comes from the 6th century CE. These are depicted in Chinese art carrying children, invalids and even emperors. These manually pulled cart-style chairs, however, were only the preserve of the rich and powerful, with wood, metal and those able to make them all in short supply. A good example of this can be seen in the inset image, which shows famous Chinese politician and philosopher Confucius being pushed around in his own bespoke wheelchair.

Wiring

Charger

Seat post The seat post sits in the middle of the systems platform and allows for a maximum weight capacity of 136kg (300lb).

Suspension Coil spring tension suspension units – both of which are adjustable from the control panel – prevent the wheels from losing purchase on the ground.

The chair’s batteries are topped up with an auxiliary, off-board charging unit. This is plugged into a mains electricity port.

Motor An electric drive motor powers the chair’s twin drive wheels, allowing a max speed of 6.4km/h (4mph) and a max range of about 30km (18.6mi).

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© Ian Moores Graphics

Electric wheelchairs are an evolution of the traditional hand-pushed wheelchair/bath chair. They function in much the same way as manual wheelchairs, granting mobility to users over a wide range of terrains and inclines, however they’re selfpropelled, with a motor doing the hard graft. As the chair is motorised, they also differ to manual wheelchairs in that they feature a systems platform beneath the seat. This platform – which is typically encased within a plastic shell – supports the motor as well as its power source (typically a battery array). The power pack is then connected via a wiring system to the motor, the seat and the wheelchair’s all-important control panel. These controls, which are generally located on one of the armrests, enable the user to operate the majority of the chair’s functions. These include seat position (both elevation and tilt), motor power for speed alterations, directional movement – delivered through a joystick, plus system diagnostics. Drive wheels on electric wheelchairs, unlike manual models, are fi xed on a single plane, with an additional set, or pair of sets, found at the front and back of the chair to take care of guidance. These guide wheels are typically fitted with variable suspension struts and springs so the wheels remain in contact with the ground even on uneven surfaces. Indeed, many modern electric wheelchairs are designed to cope with robust terrains, with large tracked wheels, reinforced pivot frames, pneumatic suspension units and high-torque motors allowing for cross-country use.

Power Two 36-amp batteries are installed at the rear of the systems platform powering the wheelchair’s electric motor and control panel.