Vol. 1, Issue 1 -- March, 1995

Robotics Feature Research

The Consumer Innovation Lab is part of the Rehabilitation Engineering Research Center (RERC) on Rehabilitation Robotics. This RERC is funded by a federal grant from the National Institute on Disability and Rehabilitation Research to the University of Delaware. The RERC supports more than a dozen individual research projects. Each issue of The Innovator will present highlights from a different one of these activities.

(Orthosis Project)

By Bob Piech & Rungun Ramanathan

Our first feature will be the Orthosis Project. An "orthosis" is defined as a device which helps to improve the use of a limb, as opposed to prosthesis which replaces lost limbs. Common examples of orthoses are leg braces or canes which assist someone to use his/her limb(s) in carrying out normal tasks. In contrast to an orthosis, devices like a wheel chair, a robotic assistant or mouth sticks help in performing tasks, but do not support the limb directly, and hence are not orthoses.

The purpose of this research is three-fold. First, we want to clearly identify a set of tasks that people with very limited movement wish to perform. Second, we want to design an orthosis to perform some of these tasks. And finally, we want to identify and evaluate how such a device can be controlled by someone who needs it. Those the device is intended to benefit would be people with weak muscles but with no loss of sensation in their arms. It was realized early in the project that a major problem faced by such people was lifting their own arm against the forces of gravity. Providing this capability would greatly increase independence. So designing an anti-gravity device was the first major task.

Project staff have designed an anti-gravity device to compensate for the weight of the person's arm giving them the feeling of weightlessness in their arms. This allows the person to move their arm using whatever strength their muscles have. An actual prototype is being constructed for evaluation.

In some instances individuals have muscles so weak that movement is very hard even after providing gravity compensation. In this case a design solution is to attach electric motors to the above passive device. The motors will operate together so that the arm will be moved in a coordinated manner in the direction which the user intends. The direction will be sensed from information gathered from very sensitive force sensors which will be placed in the cradle where the arm will be supported.

There are many details to be resolved before making a final design. In the passive version of the device, there is presently no ability to adjust for the added weight encountered when picking up a book, cup, etc. The powered design has its weakness in that the movement of a person's arm tends to be jerky. There is also the question of what is important to control? Should attention be focussed on the applied force or the speed of movement or the position or some combination of these.

Looking to the future, the researchers are working on appropriately refining the devices to accommodate specific activities in home, school or work environments. Some consumer input would help greatly. If you have very limited arm strength and mobility, what specific things might you want to use these devices to do? Please call, write or e-mail us with your comments. See The Innovator Main Page for the necessary contact information.

For more information, check out the Orthosis Home Page.