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Professor And Former Graduate Student Create All-Terrain Wheelchair

Apoorva Mandavilli in New York

On a warm, sunny and perfectly ordinary spring day nine years ago, an elderly man in a wheelchair grappled with the hilly terrain of a park near the Delaware water gap. As the man struggled over obstacles with the help of his companion, he could have had no idea that his exertions would inspire the idea of a walking, climbing wheelchair.

Because in that same park, just a few feet away, Dr Vijay Kumar, a professor of mechanical engineering at the University of Pennsylvania, was idly strolling with his wife, Maneesha. As he watched the man in the wheelchair, Dr Kumar, thought, "Wouldn't it be great if the chair could walk like people can?"

Most wheelchairs available today are sophisticated, with automated controls and advanced navigational abilities. There have also been significant improvements in urban and suburban landscapes with curb cuts, ramps and elevators to improve the access available to wheelchair users.

But people bound to wheelchairs are still denied the pleasures of beaches, parks and gardens and can often be deterred by a small, seemingly insurmountable obstacle.

"It wasn't clear that a walking chair would do the job," said Dr Kumar who set to work on the 'all-terrain' wheelchair soon after that spring day. Instead, he wanted to design "a wheelchair with crutches to hoist up over obstacles."

A couple of months ago, Dr Kumar, 37, and his former graduate student, Dr Venkat Krovi, announced the functional prototype of a wheelchair that can climb stairs, navigate grassy surfaces and clear obstacles.

The wheelchair in question is essentially a conventional wheelchair fitted with two extra limbs. The extra set of arms can climb over curbs and step over obstacles in the path of the user. They can also be used to open doors and to pick up objects.

The seat of the wheelchair is taken from an ordinary classroom chair and sits in an aluminium frame. The weight of the entire chair is evenly distributed over the point where it touches the ground. There are two rubber tires in back, and two castors in front. The chair is powered by six motors, two for the rear wheels and two for each arm. The motors are controlled by a personal computer wired to the chair that tells the motors what to do.

To climb a stair, the arms, like crutches, first anchor the chair on a step or other obstacle. The motors enable the arms to pull the wheelchair up and over the obstacle. The arms then rotate behind the chair to push the rear end of the vehicle.

The wheelchair is designed such that the arms are set in motion only when they encounter a challenge such as potholes, rocks or other obstacles and to navigate sandy beaches and grassy lawns where conventional wheelchairs are inadequate. On ordinary surfaces, the vehicle functions like a conventional wheelchair. Ideally, the arms could also be used to help the user mount and dismount the chair, so that they have a greater degree of independence in their movements.

Dr Kumar is associated with University of Pennsylvania's General Robotics Automation Sensing and Perception Center. At GRASP, nearly 50 scientists from the physical and biological sciences study locomotion -- or movement. By studying the motion of insects and goats, the scientists design machines that can walk as skilfully as goats or spiders do.

The all-terrain wheelchair has not yet been licensed for commercial development and in its current version, has several limitations. Because of the way the model is designed, the wheelchair can only climb stairs that are as "deep" as the wheelchair itself, and is currently supported by smaller motors than would be needed for an adult user.

The model, designed on a shoestring budget, can only support a maximum weight of 60 lbs (Dr Kumar's five-year-old daughter, Priya, tested the model). For adults, the model can be scaled up using bigger motors.

Dr Kumar is surprised by the amount of attention the wheelchair has attracted. But what would be even more welcome, he said, is finance for a bigger model of the wheelchair. Although many individuals have expressed interest, he said, the wheelchair industry is fairly conservative.

"Since the (wheelchair) industry is tied to the healthcare system and is indirectly regulated, there is not a lot of incentive to change," he said.

"If somehow we're able to figure out how to build robots and assist people that would be a great accomplishment," he said. In fact, he continued, it would not be unreasonable in the future to have special purpose robotic servants and families with a "fleet of personal robots."

Apoorva Mandavilli, a science writer, studies journalism at New York University.

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