Powered Mobility Sean Loughran D07117735 DT202\Inclusive Learning through Technology assignment1
What we will cover • 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 • 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
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 Non-Proportional Standard joystick Switch Sip and puff Switch array Finger joystick Mini joystick 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
These are the most common • 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.
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 • Albert M. Cook, Susan M. Hussey 2002 Assistive technologies: principles and practice • Learner J, Beverly J, 2008, Learning Disabilities and Related Mild Disabilities • Chan J, Davey C, Bath Institute of Medical Engineer, Buyers Guide Add on power devices for manual wheelchairs Aug 2008 • D.A. Hobson,September 1999, viewed 10th May 2010http://www.wheelchairnet.org/ • DX System Manual, Dynamic Controls, http://www.dynamiccontrols.com/index.cfm/1,81,html • Wikipedia, Mobility scooter, viewed10th May 2010 • <http://en.wikipedia.org/wiki/Mobility_scooter>