Transcript Powered Mobility

Powered Mobility
Sean Loughran
D07117735
DT202\Inclusive Learning through
Technology assignment1
What we will cover
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Introduction
Types of powered mobility
Outcomes
Components of a powered wheelchair
Future designs
What is powered mobility?
• Means of independent mobility for
wheelchair users
• It is not limited to those who cannot
manually self propel
• And its not limited to those who cannot
walk
• Mobility is essential for self-car, work,
school, play or leisure
• Intentional movement and active
exploration is critical in the development of
a child’s knowledge concerning his body,
his movement and his environment
(Lewis B.J.)
Mobility Scooters
Similar to a powered wheelchairs but
have handlebars to steer
The seat usually swivels to allow
access
Tend to be used for individuals that
have a systemic or whole-body
disabling conditions such as coronary
or lung issues or some forms of
arthritis.
Add-on Power devices
Add-on Power devices provide motorised power
to the standard manual wheelchair
Some are designed either to
• assist the attendant push the wheelchair
• assist the user to self-propel the
wheelchair manually
• or to convert the manual chair into a
powered wheelchair controlled by a
joystick.
A key feature is that they can be easily attached
to and removed from the manual wheelchair
Motor and battery built
into the hub of the wheel
Powered wheelchair
• Rear wheel, Mid wheel and Front
wheel drive versions
• Indoor and outdoor
• Typically controlled by a joystick
but there are various other inputs
• Tilt-in-space and reclining
systems are available
Positive outcomes
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Increased functional ability
Greater social inclusion
Access to education and employment
Reduced dependence on carers
Reduced fatigue
Better performance & efficiency
Negative outcomes
• Access adaptations such as wheelchair spaces
on public transport and wheelchair lifts are
frequently designed around a typical manual
wheelchairs
• Because of the weight and size they typically
cannot be self propelled by the user
• Require daily charging
• Generally non-foldable and requiring tie-downs
in a van for transportation
• Expensive
History
• 1950s - Everest & Jennings (USA) developed the first
powered wheelchair
• 1980s - wheelchairs now were microprocessor-controlled
and provided customization of controls to meet the need
• 1980-90s - the revolution in powered wheelchair design
with various new controls, styles, range in distance,
suspension, maneuverability, and seating options
Major System Components
An input device is used by the user to
specify velocity and directional when
driving or to navigate within a menu
displayed on the controller
Various types
– Proportional (joystick).
– Non-proportional (switch inputs, sip and
puff).
• Scan-control can be used to reduce the number
of switches required
Proportional
Standard
joystick
Finger
joystick
Mini
joystick
Non-Proportional
Switch
Sip and puff
Switch
array
Switch
scanner
• Microprocessor-based
• The controller translates signal from the input
device to a velocity and direction command for
the power controller
• If provides feedback to the user via the display
• Monitors performance of wheelchair
• Contains the custom adjustable control
parameters of the chair
What controller parameters do you
think may be adjusted for a user?
These are the most common
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Max speed
Acceleration
Deceleration
Turning speed,
Turning acceleration
Turning deceleration
• The battery provides the energy for the
power wheelchair to drive
• They are connected to the Power controller
• 24V (commonly 2 x 12V)
• Lead-Acid / Deep Cycle Gel Cell
• Rated capacity: 20 – 120 Ah
• However higher continuous
discharge currents
dramatically reduces the
available battery capacity.
– e.g. Rated capacity = 20Ah
discharge current = 20A
Battery last for only 30 minutes
instead the expected 1hr
– Therefore it is recommended to use
batteries with a capacity that is at
least twice as high as the average
discharge current.
Battery Protection
• To protect the batteries and
the system cables from
external short circuits a
thermal circuit is installed
• If the battery Voltage falls
below 21V damage to the
battery may occur. The
controller alerts the user of
low voltage condition.
Typically controller reduces
the performance of the
power chair.
Why are the use of “gel-cell”
batteries an important safety
issue?
“gel-cell” batteries are sealed and
so no acid will leak in the event
that the chair falls over
• The Power Controller sends the power to
the motors and to the other modules
• It controls the electrical energy delivered to
the motors.
• Common type is a Pulse width modulated
DC to DC converter
• The motors control the power
wheelchair speed and direction
• 24V AC or DC
• resistance of different motor types
varies typically between 20 and 350
mΩ
• Current rating 60 – 120 A
• Fail-safe electro-magnetic parkbrakes
attached to the motors prevent the
power chair moving when it is not
actively driven or when the power is
turned off.
How is a wheelchair with two
motors steered?
Motors rotate wheels at different
speeds
The turning angle is relative to the
difference
Think-Pair-Share
If you had an accident which
resulted in you requiring the use
of a wheelchair, how would it
effect your college/work life,
social life or your leisure
activities?
Modern power chairs now have the
options to control a PC, mobile phone
or aspects of the environment
Could this be the future
electric drive motor with gyroscopic
sensors to help the driver to move
Summary and finish up
• Mobility is essential for quality of life
• Powered mobility provides a means of
independence
• There are various types of powered
mobility devices to suit a user needs
• Enables the user to have control of their
environment
Bibliography
1. Albert M. Cook, Susan M. Hussey 2002 Assistive technologies: principles
and practice
2. Learner J, Beverly J, 2008, Learning Disabilities and Related Mild
Disabilities
3. Chan J, Davey C, Bath Institute of Medical Engineer, Buyers Guide Add
on power devices for manual wheelchairs Aug 2008
4. D.A. Hobson,September 1999, viewed 10th May 2010
http://www.wheelchairnet.org/
5. DX System Manual, Dynamic Controls,
http://www.dynamiccontrols.com/index.cfm/1,81,html
6. Wikipedia, Mobility scooter, viewed 10th May 2010
<http://en.wikipedia.org/wiki/Mobility_scooter>