Wheelchair

Powered Wheelchair Information for High-Level Quadriplegics

Criteria for Purchasing a Powered Wheelchair

This section is written to help a recently injured high-level quadriplegic avoid the pitfalls of a poorly designed power wheelchair.

Mark believes that a powered wheelchair should maneuver outside as easily as it maneuvers on a flat surface inside a building. Mark has identified several criteria that he believes are essential for a wheelchair to maneuver properly both inside and outside. Note: The following criteria is based solely on Mark's experience over the last 32 years of being in a wheelchair. Recently injured high-level quadriplegic should consult a physical therapist for their particular situation.

Powered Wheelchair Frame Criteria
for Indoor or Outdoor

• The wheelchair should be equipped with two deep cycle marine gel cell batteries. When fully charged, these batteries should provide a wheelchair user a 10 to 20 mile driving range. The marine deep cycle gel cell batteries are expensive but they are worth the cost. A routinely charged gel cell batteries can last for up to five years and they are practically maintenance-free. Note: Do not let these batteries completely discharge. They will never hold another charge of any kind.

• The batteries should be mounted in the middle of the wheelchair frame. Two deep- cycle marine gel cell batteries can weigh up to 150 pounds. This weight can be used to either stabilize or destabilize the balance of the wheelchair. When the batteries are mounted on the back of a wheelchair frame, the wheelchair is prone to flipping backward when going up an incline. If a wheelchair has the batteries mounted in the center of the frame, the battery weight inhibits the wheelchair from flipping over when going up an incline.

• The powered wheelchair tires should be foam filled. Again, they are expensive but they are virtually maintenance-free. Mark has found that these tires will last about 2000 miles.

• The powered wheelchair drive tires should be from 5 to 12 inches high and 3 to 5 inches wide. The bigger the tire, the easier it is for the wheelchair to roll over holes, branches, or rough terrain. One disadvantage of large tires is that they will create more friction on the ground. Fixed-positioned turns will be more difficult for the wheelchair because the motors have to overcome the extra friction from the larger tires. Mark uses go-kart tires.

• The powered wheelchair's drive wheels should be mounted either in the front or the back of the wheelchair frame. If the wheelchair's drive wheels are mounted in the middle of the wheelchair, the wheelchair will tend to throw the wheelchair user forward when going from a flat surface to a steep drop-off. Middle-drive wheelchairs do have the advantage of making very tight fixed-positioned turns and work well indoors in tight maneuvering situations. Mark does not believe that tight fixed positioned-turns out weigh the danger of being whipped forward when going down steep drop-offs.

Powered Wheelchair Seat Criteria
for a High-Level Quadriplegic

• The powered wheelchair seat should be a recliner. The backrest of the seat should tilt back while the leg rests should move out and up. This lets the wheelchair user take the sitting pressure off of their rear and stretch their legs out to reduce swelling in the user's legs. Some wheelchair recliners tilt the entire seat but do not stretch out the leg rests. This type of recliner keeps the wheelchair user's hips bent and does not reduce leg swelling as well as a recliner that kicks out the leg rests.

• The powered wheelchair seat recliner should only have one motor. Some recliner seats use multiple motors. These recliners can be a nightmare to maintain.

• The powered wheelchair seat should have a headrest so that the wheelchair user can rest their neck during the day or sleep during the day without having to get into bed. The headrest should also have a kill switch that stops the wheelchair motor controller. A user would typically bump their heads against a switch on the headrest to stop the movement of the wheelchair motors. This is necessary if the wheelchair users control mechanism is not functioning properly or is out of position.

• The powered wheelchair seat should have trough armrests to give the wheelchair users elbows and shoulders support. When a wheelchair users arms are hanging down all day and every day, eventually the weight of the users arms causes the shoulder socket joints to separate. This can be very painful. Mark uses egg crate mattress foam under his elbows to avoid pressure sores.

• A powered wheelchair seat should have a seat cushion. This will help a wheelchair user avoid pressure sores on their rear. Mark uses a ROHO high-profile seat cushion. A newly injured high-level quadriplegic should consult with a physical therapist to choose a seat cushion that is appropriate for the user's situation.

Sip and Puff Wheelchair Motor Controller Project

Since the early 90's, Bill Beltz and Mark Sterle have been building wheelchair controllers for high-level quadriplegics. Bill Beltz is a scientific instrument maker for veterinary medical research and Mark Sterle has been a professional programmer for 20 years. Since Mark has been a high-level quadriplegic for over 30 years, Bill and Mark have a very good understanding of the requirements of a wheelchair controller for quadriplegics. Together, they have built a wheelchair controller that will have a dramatic impact on the mobility and environmental control of a high-level quadriplegic.

Air pressure, commonly known as SIP and PUFF control, is used as the means of wheelchair control for the following reasons :

• Arm movement is not required to control the wheelchair motors or their environmental controls.

• Rough terrain does not affect the user's ability to control the wheelchair. For instance, when Mark drives through rough terrain, the force of the wheelchair moves Mark around in the chair. Since he holds the control tube in his mouth, the tube moves with him as he rides over bumps and does not affect his steering.

• An electronic device does not need to be mounted in front of the wheelchair users face. Mark has a small tube to his mouth that he can move out of his way when he needs to type on a computer.

The Sip and Puff wheelchair controller is based on 5 different air pressure states.

• Hard Sip

• Soft Sip

• No Sip or Puff

• Soft Puff

• Hard Puff

With these 5 air pressures, Mark has demonstrated that the Sip and Puff control is more than adequate to precisely navigate a wheelchair or control his environment. The wheelchair controller has the following functionality :

• Three Drive Modes

  • Continuous Drive Motor Ramp Up and Ramp Down Control

  • Multi-Speed Drive Motor Ramp Up Control

  • Continuous Multi-Speed Drive Motor Ramp Up Control

• Wheelchair Seat Recline and Incline Motor Control

• Environmental Control

• 3 Auto Latched or Unlatched Aux Switch Outputs

• Battery Low Beeper

• System Fault Detection

• Headrest Recline or Incline Switch Fault Tolerance

• System Configuration Parameter Settings

• Dynamic Braking

Over the last several years, Mark has run their controllers for literally thousands of miles through streets, campuses, and through many other rough terrains without incident. The following video files demonstrate the controller.

Wheelchair Controller Demonstration Videos

Austin

Figure 8s (2 MB)
Up a Sidewalk (1 MB)
Bridge Crossing (1 MB)
Barrel Roll (1 MB)
Passing By (2 MB)

Figure 8s (2 Megs)

Up a Sidewalk (1 Megs)

Bridge Crossing (1 Megs)

Barrel Roll (1 Megs)

Passing By (2 Megs)