There are a wide variety of types of wheelchairs, differing by propulsion method, mechanisms of control, and technology used. Some wheelchairs are designed for general everyday use, others for single activities, or to address specific access needs. Innovation within the wheelchair industry is relatively common, but many innovations ultimately fall by the wayside, either from over-specialization or from failing to come to market at an accessible price point. The
iBOT is perhaps the best-known example of this in recent years.
Manual self-propelled wheelchairs hospital, Sweden A self-propelled
manual wheelchair incorporates a frame, seat, one or two footplates (footrests), and four wheels: usually two caster wheels at the front and two large wheels at the back. There will generally also be a separate seat cushion. The larger rear wheels usually have push-rims of slightly smaller diameter projecting just beyond the tyre; these allow the user to manoeuvre the chair by pushing on them without requiring them to grasp the tyres. Manual wheelchairs generally have brakes that bear on the tyres of the rear wheels, however, these are solely a parking brakes and in-motion braking is provided by the user's palms bearing directly on the push-rims. As this causes friction and heat build-up, particularly on long downslopes, many wheelchair users will choose to wear padded wheelchair gloves. Manual wheelchairs often have two push handles at the upper rear of the frame to allow for manual propulsion by a second person; however, many active wheelchair users will remove these to prevent unwanted pushing from people who believe they are being helpful. Everyday manual wheelchairs come in two major varieties, folding or rigid. Folding chairs are generally low-end designs, whose predominant advantage is being able to fold, generally by bringing the two sides together. This is an advantage for people who need to store the wheelchair frequently or to put it in a small vehicle. Rigid wheelchairs have permanently welded joints and many fewer moving parts. This reduces the energy required to push the chair by eliminating many points where the chair would flex and absorb energy as it moves. Welded rather than folding joints also reduce the overall weight of the chair. Rigid chairs typically feature instant-release rear wheels and backrests that fold down flat, allowing the user to dismantle the chair quickly for storage in a car. A few wheelchairs attempt to combine the features of both designs by providing a fold-to-rigid mechanism in which the joints are mechanically locked when the wheelchair is in use. Many rigid models are made with light materials such as
aluminium and
titanium, and wheelchairs of composite materials such as carbon-fibre have started to appear. Ultra lightweight rigid wheelchairs are commonly known as 'active user chairs' as they are ideally suited to independent use. Another innovation in rigid chair design is the installation of shock absorbers, such as "Frog Legs", which cushion the bumps over which the chair rolls. These shock absorbers may be added to the front wheels, to the rear wheels, or both. Rigid chairs also have the option for their rear wheels to have a camber, or tilt, which angles the tops of the wheels in toward the chair. This allows for more mechanically efficient propulsion by the user and also makes it easier to hold a straight line while moving across a slope. Sport wheelchairs often have large camber angles to improve stability. Rigid-framed chairs are generally made to measure, to suit both the specific size of the user and their needs and preferences around areas such as the "tippyness" of the chair – determined by the distance between the
center of gravity and the rear axle. Experienced users with sufficient upper-body strength can generally balance the chair on its rear wheels, a "wheelie", and the "tippyness" of the chair controls the ease with which this can be initiated. The wheelie allows a wheelchair user to climb and descend curbs and move more easily over small obstacles and irregular ground such as cobbles. The rear wheels of self-propelled wheelchairs typically range from in diameter, and commonly resemble bicycle wheels. Wheels are rubber-tired and may be solid, pneumatic or gel-filled. The wheels of folding chairs may be permanently attached, but those for rigid chairs are commonly fitted with quick-release axles activated by depressing a button at the centre of the wheel. All major varieties of wheelchairs can be highly customized for the user's needs. Such customization may encompass the seat dimensions, height, seat angle, footplates, leg rests, front
caster outriggers, adjustable backrests and controls. Various optional accessories are available, such as anti-tip bars or wheels, safety belts, adjustable backrests, tilt and/or recline features, extra support for limbs or head and neck, holders for
crutches, walkers or oxygen tanks, drink holders, and mud and wheel-guards as clothing protectors. Light weight and high costs are related to the manual wheelchair market. At the low-cost end, heavy, folding steel chairs with sling seats and little adaptability dominate. Users may be temporarily disabled, or using such a chair as a loaner, or simply unable to afford better. These chairs are common as "loaners" at large facilities such as airports, amusement parks and shopping centers. A slightly higher price band sees the same folding design produced in aluminium. The high end of the market contains ultra-light models, extensive seating options and accessories, all-terrain features, and so forth. The most expensive manual chairs may rival the cost of a small car.
Manual attendant-propelled wheelchairs An attendant-propelled wheelchair (also known as a companion or transport chair) is generally similar to a self-propelled manual wheelchair, but with small diameter wheels at both front and rear. The chair is maneuvered and controlled by a person standing at the rear and pushing on handles incorporated into the frame. Braking is supplied directly by the attendant who will usually also be provided with a foot- or hand-operated parking brake. These chairs are common in institutional settings and as loaner-chairs in large public venues. They are usually constructed from steel as light weight is less of a concern when the user is not required to self-propel. Specially designed transfer chairs are now required features at airports in much of the developed world in order to allow access down narrow airliner aisles and facilitate the transfer of wheelchair-using passengers to and from their seats on the aircraft.
Powered wheelchairs An electric-powered wheelchair, commonly called a "powerchair," incorporates batteries and
electric motors into the frame and is controlled by either the user or an attendant, most commonly via a small joystick mounted on the armrest, or on the upper rear of the frame. Alternatives exist for the traditional manual joystick, including head switches, chin-operated joysticks,
sip-and-puff controllers or other specialist controls, which may allow independent operation of the wheelchair for a wider population of users with varying motor impairments. Ranges of over 10 miles/15 km are commonly available from standard batteries. Powerchairs are commonly divided by their access capabilities. An indoor-chair may only reliably be able to cross completely flat surfaces, limiting them to household use. An indoor-outdoor chair is less limited, but may have restricted range or ability to deal with slopes or uneven surfaces. An outdoor chair is more capable, but will still have a very restricted ability to deal with rough terrain. A very few specialist designs offer a true cross-country capability. Powerchairs have access to the full range of wheelchair options, including ones that are difficult to provide in an unpowered manual chair, but have the disadvantage of significant extra weight. Where an ultra-lightweight manual chair may weigh under 10 kg, the largest outdoor power-chairs may weigh 200 kg or more. Smaller power chairs often have four wheels, with front or rear wheel drive, but large outdoor designs commonly have six wheels, with small wheels at front and rear and somewhat larger powered wheels in the centre. A power-assisted wheelchair is a recent development that uses the frame and seating of a typical rigid manual chair while replacing the standard rear wheels with wheels of similar size which incorporate batteries and battery-powered motors in the hubs. A floating rim design senses the pressure applied by the user's push and activates the motors proportionately to provide a power assist. This results in the convenience, and small size of a manual chair while providing motorised assistance for rough/uneven terrain and steep slopes that would otherwise be difficult or impossible to navigate, especially by those with limited upper-body function. As the wheels necessarily come at a weight penalty it is often possible to exchange them with standard wheels to match the capabilities of the wheelchair to the current activity.
Mobility scooters Mobility scooters share some features with powerchairs, but primarily address a different market segment, people with a limited ability to walk, but who might not otherwise consider themselves disabled. Smaller mobility scooters are typically three wheeled, with a base on which is mounted a basic seat at the rear, with a control tiller at the front. Larger scooters are frequently four-wheeled, with a much more substantial seat. Opinions are often polarized as to whether mobility scooters should be considered wheelchairs or not, and negative stereotyping of scooter users can be worse than for some manual or power-chair users. Some commercial organisations draw a distinction between power-chairs and scooters when making access provisions due to a lack of clarity in the law as to whether scooters fall under the same equality legislation as wheelchairs.
Single-arm drive wheelchairs One-arm or single arm drive enables a user to self-propel a manual wheelchair using only a single arm. The large wheel on the same side as the arm to be used is fitted with two concentric handrims, one of smaller diameter than the other. On most models the outer, smaller rim, is connected to the wheel on the opposite side by an inner concentric axle. When both handrims are grasped together, the chair may be propelled forward or backward in a straight line. When either handrim is moved independently, only a single wheel is used and the chair will turn left or right in response to the handrim used. Some wheelchairs, designed for use by
hemiplegics, provide a similar function by linking both wheels rigidly together and using one of the footplates to control steering via a linkage to the front caster.
Reclining and tilting wheelchairs Reclining or tilt-in-space wheelchairs have seating surfaces that can be tilted to various angles. The original concept was developed by an orthotist, Hugh Barclay, who worked with disabled children and observed that postural deformities such as scoliosis could be supported or partially corrected by allowing the wheelchair user to relax in a tilted position. The feature is also of value to users who are unable to sit upright for extended periods for pain or other reasons. In the case of
reclining wheelchairs, the seat-back tilts back, and the leg rests can be raised, while the seat base remains in the same position, somewhat similar to a common
recliner chair. Some reclining wheelchairs lean back far enough that the user can lie down completely flat. Reclining wheelchairs are preferred in some cases for some medical purposes, such as reducing the risk of pressure sores, providing passive movement of hip and knee joints, and making it easier to perform some nursing procedures, such as intermittent catheterization to empty the bladder and transfers to beds, and also for personal reasons, such as people who like using an attached tray. The use of reclining wheelchairs is particularly common among people with spinal cord injuries such as quadriplegia.
Wheelchair stretchers Wheelchair stretchers are a variant of wheeled stretchers/gurneys that can accommodate a sitting patient, or be adjusted to lie flat to help in the lateral (or supine) transfer of a patient from a bed to the chair or back. Once transferred, the stretcher can be adjusted to allow the patient to assume a sitting position.
All-terrain wheelchairs All-terrain wheelchairs can allow users to access terrain otherwise completely inaccessible to a wheelchair user. Two different formats have been developed. One hybridises wheelchair and mountain bike technology, generally taking the form of a frame within which the user sits and with four mountain bike wheels at the corners. In general, there are no push-rims and propulsion/braking is by pushing directly on the tyres. A more common variant is the beach wheelchair (beach-going wheelchair) which can allow better mobility on beach sand, including in the water, on uneven terrain, and even on snow. The common adaptation among the different designs is that they have extra-wide balloon wheels or tires, to increase stability and decrease ground pressure on uneven or unsteady terrain. Different models are available, both manual and battery-driven. In some countries in Europe, where
accessible tourism is well established, many beaches have wheelchairs of this type available for loan/hire.
Smart wheelchairs A smart wheelchair is any powerchair using a
control system to augment or replace
user control. Its purpose is to reduce or eliminate the user's task of driving a powerchair. Usually, a smart wheelchair is controlled via a
computer, has a suite of
sensors and applies techniques in mobile
robotics, but this is not necessary. The type of sensors most frequently used by smart wheelchairs are the ultrasonic acoustic range finder (i.e.
sonar) and
infrared red (IR) range finder. The interface may consist of a conventional wheelchair joystick, a "
sip-and-puff" device or a touch-sensitive display. This differs from a conventional powerchair, in which the user exerts manual control over speed and direction without intervention by the wheelchair's control system. Smart wheelchairs are designed for a variety of user types. Some are designed for users with
cognitive impairments, such as
dementia, these typically apply collision-avoidance techniques to ensure that users do not accidentally select a drive command that results in a collision. Others focus on users living with severe motor disabilities, such as
cerebral palsy, or with
quadriplegia, and the role of the smart wheelchair is to interpret small muscular activations as high-level commands and execute them. Such wheelchairs typically employ techniques from
artificial intelligence, such as
path-planning.
Technological developments Recent technological advances are slowly improving wheelchair and powerchair technology. A variation on the manually propelled wheelchair is the Leveraged Freedom Chair (LFC), designed by the
MIT Mobility Lab. This wheelchair is designed to be low-cost, constructed with local materials, for users in developing countries. Engineering modifications have added hand-controlled levers to the LFC, to enable users to move the chair over uneven ground and minor obstacles, such as bumpy dirt roads, that are common in developing countries. It is under development, and has been tested in Kenya and India so far. The addition of geared, all-mechanical wheels for manual wheelchairs is a new development incorporating a
hypocycloidal
reduction gear into the wheel design. The 2-gear wheels can be added to a manual wheelchair. The geared wheels provide a user with additional assistance by providing leverage through gearing (like a bicycle, not a motor). The two-gear wheels offer two speed ratios- 1:1 (no help, no extra torque) and 2:1, providing 100% more hill climbing force. The
low gear incorporates an automatic "hill hold" function which holds the wheelchair in place on a hill between pushes, but will allow the user to override the hill hold to roll the wheels backward if needed. The low gear also provides downhill control when descending. A recent development related to wheelchairs is the
handcycle. They come in a variety of forms, from the road and track racing models to off-road types modelled after
mountain bikes. While dedicated handcycle designs are manufactured, clip-on versions are available that can convert a manual wheelchair to a handcycle in seconds. The general concept is a clip-on front-fork with hand-pedals, usually attaching to a mounting on the footplate. A somewhat related concept is the Freewheel, a large dolley wheel attaching to the front of a manual wheelchair, again generally to the footplate mounting, which improves wheelchair performance over rough terrain. Unlike a handcycle, a wheelchair with a Freewheel continues to be propelled via the rear wheels. There are several types of hybrid-powered handcycles where hand-pedals and used along with the electrical motor that helps on hills and large distances. The most recent generation of clip-on handcycles is fully electrical
wheelchair power add-ons that use
lithium-ion battery,
brushless DC electric motor and light-weight aluminium frames with easy to attach clamps to convert almost any manual wheelchair into electrical trike in seconds. That makes long-distance journeys and everyday tasks much easier and keeps wheelchair users hands clean. There have been significant efforts over the past 20 years to develop stationary
wheelchair trainer platforms that could enable wheelchair users to exercise as one would on a
treadmill or
bicycle trainer. Some devices have been created that could be used in conjunction with virtual travel and interactive gaming similar to an
omnidirectional treadmill. This convergence of virtual reality and a treadmill have been used for pediatric and adult rehabilitation to regain walking skills. In 2011, British inventor Andrew Slorance developed
Carbon Black the first wheelchair to be made almost entirely out of
carbon fiber Recently,
EPFL's CNBI project has succeeded in making wheelchairs that can be controlled by brain impulses. Interest in electric-powered wheelchairs that are able to climb stairs has increased over the past twenty years. Therefore, many
electric wheelchairs with the ability to climb stairs have been developed. Electric-powered wheelchairs with climbing ability need to be stronger and have greater movement in comparison to an electric-powered wheelchair that cannot climb stairs. They must also be stable in order to prevent injury to the wheelchair user. There are currently a number of electric powered wheelchairs that are able to climb stairs available to purchase. Technical developments are continuing in this area. Experiments have also been made with unusual variant wheels, like the
omniwheel or the
Mecanum wheel. These allow for a broader spectrum of movement, but have made no mass-market penetration. The
electric wheelchair shown on the right is fitted with Mecanum wheels (sometimes known as Ilon wheels) which give it complete freedom of movement. It can be driven forwards, backward, sideways, and diagonally, and also turned around on the spot or turned around while moving, all operated from a simple joystick. Beach wheelchair Netherlands.jpg|A beach wheelchair at a public beach in the Netherlands Snow wheelchair.jpg|A snow wheelchair at an outdoor park Leveraged wheelchair Kenya.jpg|A Leveraged Freedom Chair wheelchair user in Kenya. The chair has been engineered to be low-cost and usable on the rough roads common in developing countries. MecanumWheelchair.jpg|Wheelchair fitted with Mecanum wheels, taken at a trade fair in the early 1980s
Other variants • Foot propulsion of a manual wheelchair by the occupant is possible for users who have limited hand movement capabilities or simply do not wish to use their hands for propulsion. Foot propulsion also allows patients to exercise their legs to increase blood flow and limit further disability. Users who do this commonly may elect to have a lower seat height and no footplate to better suit the wheelchair to their needs. •
Wheelbase chairs are powered or manual wheelchairs with especially
molded seating systems interfaced with them for users with a more complicated
posture. A molded seating system involves taking a cast of a person's best achievable seated position and then either carving the shape from
memory foam or forming a plastic mesh around it. This seat is then covered, framed, and attached to a wheelbase. • A
bariatric wheelchair is one designed to support larger weights; most standard chairs are designed to support no more than 250 lb (113 kg) on average. •
Pediatric wheelchairs are another available subset of wheelchairs. These can address needs such as being able to play on the floor with other children, or cater for children in large hip-spica casts due to problems such as hip dysplasia. •
Hemi wheelchairs have lower seats which are designed for easy foot propulsion. The decreased seat height also allows them to be used by children and shorter individuals. • A
knee scooter is a related device with some features of a wheelchair and some walking aids. Unlike wheelchairs they are only suitable for below knee injuries to a single leg. The user rests the injured leg on the scooter, grasps the handlebars, and pushes with the uninjured leg. • Some
walkers can be used as a wheelchair. These walkers have seat and foot plates, so an attendant can push while the patient is sitting on the walker. This is useful for a person who gets tired while walking with a walker, or has a limited walking range meaning the person can walk, but after a while, the person will collapse and fall to the ground. • A
commode wheelchair is a wheelchair made for the bathroom. A commode wheelchair has a hole in the seat so the user does not have to transfer into the toilet. Sometimes the hole can be covered. Sometimes there is a pan attached to the hole, so the user can urinate/defecate without having to wheel over the toilet. == Mobility and access ==