ROSSLYN, Va., March 30, 1998 --- By studying how goats and spiders get around, a biomedical engineer at the University of Pennsylvania has designed and patented an all-terrain wheelchair that can climb up to 12-inch steps and amble over obstacles.
The prototype vehicle has powered rear wheels and two robotic arms that anchor the chair like crutches or ski poles and pull it from the front or push it from behind. To climb a stair, the arms pull the wheelchair up and over the raised ledge then rotate behind the device to push the rear end up and onto the elevated step. (The wheelchair cannot climb stairs narrower than the vehicle itself.)
The wheelchair is designed to cross potholes; hobble over tree limbs, rocks or other obstacles; and cruise along sandy beaches where conventional wheelchairs bog down. Vijay Kumar, Ph.D., an associate professor in the School of Engineering and Applied Science at Penn, developed the vehicle with support from The Whitaker Foundation and the National Science Foundation.
Kumar said he began to think about alternative wheelchair designs nearly 10 years ago after watching an elderly man's unsuccessful struggle to push his wheelchair over a step in a park. Kumar and colleagues at Penn's General Robotics and Active Sensory Perception (GRASP) Lab specialize in designing machines that can walk as nimbly as goats or spiders do.
"Insects and goats represent the ends of the spectrum of models for walking vehicles," Kumar said. For the wheelchair, Kumar and his research group followed the model of the spider, which keeps its body supported and stable while walking. Goats, while nimble, are unstable during the brief times that all their feet are off the ground, the same as humans.
The wheelchair has an aluminum frame with the plastic seat from a desk chair mounted on top, two rubber tires in back, and two casters in front. Six motors drive the robotic arms and rear wheels, all controlled by a personal computer wired to the vehicle.
The dimensions of the wheelchair were carefully calculated to distribute the weight of the device over the points where it touches the ground. The prototype will support a rider who weighs up to 60 pounds, the weight of the wheelchair itself.
Kumar is refining the design of the arms so they will be more useful for such tasks as opening doors or grasping objects. "The arms could also be used to help the user mount and dismount the chair, giving a greater degree of independence," he said. For comfort, the prototype's stationary seat could be replaced with a seat that slides to remain level when the chair tilts.
The all-terrain wheelchair has not yet been licensed for commercial development.
Contact:
Frank Blanchard
(703) 528-2430
fb@whitaker.org
Digital Video and Photos:
http://www.cis.upenn.edu/~venkat/wheel_noframe.html
Video Tape:
Ann Davis
(215) 898-1422
anndavis@pobox.upenn.edu