Using two motors, speech-recognition software and an exo-skeleton inspired by science fiction, three undergraduates in the Whiting School of Engineering this year designed and built a muscle-enhancement device that will help a disabled man grasp and lift a cup, a book and other household items.
The motorized plastic shell will fit over the right arm of the man, who has an extremely rare degenerative muscle disorder called inclusion body myositis. By uttering commands such as "open" and "raise," the man will receive mechanical help in moving his fingers and bending his elbow.
This device, which could be adapted for other people with disabilities, was developed during two semesters by students in the Department of Mechanical Engineering's Senior Design Project course. The project originated last summer when the man with the muscle disease sought help from Volunteers for Medical Engineering, a nonprofit Baltimore group that uses technology to assist people with disabilities. The client explained that his nerves were intact, meaning that he could control the placement of his fingers around an object, but progressive muscle deterioration had left him unable to grasp and lift even small objects.
To help him, the VME sponsored a project in the Johns Hopkins course. The task of designing and building the device went to a mechanical engineering major, Jonathan Hofeller from Needham, Mass., and two biomedical engineering majors, Christina Peace from Baltimore and Nathaniel Young from Dayton, Ohio.
The students researched prosthetic limbs and, taking a cue from props featured in the film Aliens, designed a plastic exo-skeleton that could slide over the client's right hand and arm. To help move his fingers and elbow, the students--after testing systems using electromagnets and air pressure systems--chose instead two small but powerful stepper motors that could move the fingers and elbow in small, slow increments, allowing the client to clasp a cup firmly without crushing it. In addition, these motors would preserve battery power because they did not require continuous electrical current to stay in position. The motors are linked to a series of cables and springs that enable the device to move the man's arm into position and help his fingers grasp and release.
The students opted for voice recognition software as an easy way to control the grasping device. Using software trained to his voice, the client can say "arm" or "hand" to take command of one of the two motors. The elbow motor will then respond to "raise," "down" or "stop"; the hand motor will respond to "open," close" and "stop." The device is hard-wired to a control box that contains a miniature computer and two programs that turn the voice commands into signals that tell the motors how to operate the bending and grasping motions. The unit is powered by a rechargeable 12-volt lead-acid battery commonly used for remote-control model boats and airplanes. The control box fits inside a small pack the man can carry on his waist, making the grasping device fully portable.
"The students did a wonderful job," said Jan Hoffberger, executive director of Volunteers for Medical Engineering. "They came up with a very creative design for the device. They purposely set it up to move very slowly, so that at any time in the grasping and lifting process, our client can tell it to stop. We believe he will find it very helpful."
The students had to work within a budget of $10,000; they ended up spending about $8,000 on the device. Designing and building it helped the undergraduates to understand some of the challenges that working engineers face. "In a textbook, there is always one right answer," Young said. "In this project, there were many different ways we could go. But once we were committed, we had to go in that direction." His teammate Hofeller said, "The project involved a lot of trial and error, but it was fun to apply what we'd been learning." The third team member, Peace, added, "When you're working out a problem in an engineering book, the conditions are ideal. In this project, the conditions were not perfect, but we still got the job done."
The grip-enhancing device was one of 11 projects completed this year in the Senior Design Project course, which is taught by Andrew F. Conn, a Johns Hopkins graduate with more than 30 years of experience in public and private research and development. Each team of two or three students, working within budgets of up to $10,000, had to design a device, purchase or fabricate the parts and assemble the final product. Corporations, government agencies and nonprofit groups provided the assignments and funding.