Wheelchairs take a stand for their users

Tom Shelley reports on an extraordinary development in electric mobility vehicles with big ramifications for the world of mobile robotics



A mobility chair that can stand up on its hind wheels is proving an extraordinary boon to its users, and points the way to all sorts of future vehicles.

Developed from the Segway self balancing human transporter, it is yet another example of why slightly weird engineering ideas are worth pursuing, even if a sensible market use for them cannot be conceived immediately.

The mobility chair is able to go up and down stairs and allow its users to be on a level with standing able bodied people. It thus gives them greatly improved quality of life while demonstrating a novel way forward for all kinds of robotic all terrain vehicles.

The iBot 4000 Mobility System is the brainchild of Dean Kamen's development team at Deka Research and Development Corporation in New Hampshire in the US, which was the originator of the Segway. Founded in 1982, the company has since come up with mostly medical products as diverse as the Homechoice Dialysis Machine, novel artery stents and the Hydroflex Irrigation Pump. The company is now nearly 200 strong and has its own on-site machine shop and moulding facility and speed prototyping and testing.

The iBot uses the same gyroscopic balancing system as the Segway but has a considerable number of enhancements. At first sight, it looks like an ordinary electric mobility chair on four wheels controlled by a joystick. However, the wheels are mounted on a four bar linkage that allows the machine to stand up and balance on the rear pair. This might sound a trivial capability but is of immense benefit for many users. Examples include a lawyer who uses it when he approaches the judge's seat in order to be able to look the judge in the eye over the top of his desk. An elderly couple is once again able to walk hand in hand and ordinary people in a social venue are able to communicate face to face at the same level. If pushed sharply, the chair automatically transitions down to four wheeled mode in a completely safe manner.

But even more remarkably, the device can be climb kerbs up to 5 inches (125mm) high in four wheeled mode and go up and down stairs. It does this by the users disabling the joystick, and moving their body weight forward and back while holding onto the hand rail, or in the case of some severely disabled users, an assistant. The body leaning motion is necessary in order to keep the wheels under the overall centre of gravity, and is taught. The pairs of wheel axles are then rotated about a common axis to perform the climbing motion. Steps can be up to 8.5 inches (216mm) high and should be at least 9 inches (229mm) wide.

The device employs a triple redundant computer control system made to aerospace quality specifications and is sold by Independence Technology, a subsidiary of Johnson and Johnson for around $26,000. It is rated for users weighing up to 250 lb: (114kg or nearly 18 stones). According to Luis Colom, a Deka design engineer who worked on the project, there are now, "Quite a few around" in the US. It is not yet on sale in other countries, although service support is available in the UK for machines purchased in North America.

From what Luis Colom said, the design work was quite a challenge. Deka is a PTC and Pro/Engineer user. The company has used other CAD packages in the past but he said, these were being, "phased out." Pro/Engineer Mechanism Design was used to analyse the four bar linkage and the mechanics of getting up and down stairs. It was originally designed using belt drives, but these were found to be a source of unreliability and have since been replaced by gear drives, which have a design life of at least five years. Files are managed by Pro/Intralink which is being upgraded to Pro/PDMLink and which will include the management of Mentor electrical and electronic files. Other software modules in use at Deka include Pro/Engineer Interactive Surface Design, Advanced Assembly and Reverse Engineering. Tooling to make die castings was made directly from Pro/Engineer models.

The original Segway, which was originally written off by many as an unnecessarily complicated novelty, is finding service in commercial enterprises and by some US police forces. It allows workers to travel short distances faster and increases their carrying capacity. with less wasted time. The same can also be said of roller skates and bicycles but roller skates require a level of skill most of us above teen age do not have, and bicycles are distinctly more cumbersome. According to a report by the Seattle Office of Sustainability and Environment, Fleets and Facilities Department, the City purchased ten Segways at $6700 each to research the costs and benefits of using them to replace vehicles in tasks such as reading water meters. The report concluded that overall cost savings were $8000 per year, mostly in productivity savings. On routes that involved mostly driving, savings were $5187 per year in reduced vehicle, fuel and maintenance costs.

Police forces find that a single battery charge allows officers to cover eight to ten miles of territory in less than half the time it takes to patrol on foot. They can also flow effortlessly with a crowd, or respond to urgent situations at 12.5 mph. Because the rider stands a head taller than everyone else, officers get a clear sightline in crowds and pedestrian environments.

The big future for the iBot technology, however, could well be in industrial and domestic robotics. Robots with two legs capable of useful work, while beloved by makers of science fiction films, mainly because they can be portrayed by human actors, have so far proved to be impractical to build. Industrial robots are mostly fixed firmly to the ground but there has been a lot of development work with domestic robots, particularly robotic vacuum cleaners, which use wheels to get around, but have real problems when encountering obstacles and no chance at all when faced with steps or stairs. While the cost of the iBot is considerable, this is mainly because of the need to ensure absolute safety when transporting vulnerable humans and its presently small scale manufacturing volume. Something very much cheaper could be devised to allow the movement of a go anywhere vacuum cleaner or other device.

Deka Research and Development Corporation
Independence Ibot 4000 Mobility System

Eureka says: Mobile robots and other vehicles may be able to follow an entirely new direction thanks to some truly inspired innovations

Pointers

* Electric mobility vehicles are able to stand up on their hind wheels and balance to bring their users up to the same level as able bodied people around them

* By users shifting their balance, the vehicles can also be made to safely make their way up and down stairs

* The principles encompassed are immensely applicable to other vehicles, especially those being developed for mobile robotic tasks

Author
Tom Shelley

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