Algorithms in the prototype device help visually impaired users avoid obstacles and find unoccupied chairs. (Source: MIT CSAIL)Researchers at MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) have developed a wearable system for people who are visually impaired that helps to give them more information about their environment.
For years, white canes have been the standard device to help visually impaired people identify clear walking paths. But canes can only do so much. They can’t determine if an object is a person or discern between a table or chair or even if someone is sitting in a chair already.
The system from MIT’s CSAIL uses a 3-D camera, a belt with separately controllable vibrational motors and an electronically reconfigurable Braille interface. The camera is worn in a pouch hung around the neck, a processing unit runs the algorithms, the sensor belt has five vibrating motors evenly spaced around its forward half and the Braille interface is worn by the user’s side.
“We did a couple of different tests with blind users,” says Robert Katzschmann, a graduate student in mechanical engineering at MIT. “Having something that didn’t infringe on their other senses was important. So we didn't want to have audio; we didn’t want to have something around the head, vibrations on the neck — all of those things, we tried them out, but none of them were accepted. We found that the one area of the body that is the least used for other senses is around your abdomen.”
How It Works
The algorithms are used to quickly identify surfaces and their orientations from the 3-D camera data. It first groups the pixels from the camera into clusters of three. Because the pixels have location data, each cluster determines a plane. If the orientations of the planes are within 10 degrees of each other, the system concludes that it has found a surface. It registers an obstacle at that location and begins to buzz the associated motor if the wearer gets within 2 meters of it.
For chair identification, the system needs to complete three distinct surface identifications in the same general area, rather than just one. This makes sure the chair is unoccupied. The surfaces need to be roughly parallel to the ground and fall within a prescribed range of heights.
The belt motors vary in frequency, intensity and duration to send different tactile signals to the user. An increase in frequency and intensity may indicate the wearer is approaching an obstacle in the direction indicated by that motor. But when finding a chair, a double pulse indicates the direction in which a chair with a vacant seat can be found.
The Braille interface is used to describe the objects in the user’s environment. A user adept at Braille should find that the signals from the Braille interface and the belt-mounted motors coincide. In tests of the wearable device, the chair-finding system reduced subjects’ contacts with objects other than the chairs by 80 percent and the navigation system reduced the number of cane collisions with people loitering around a hallway by 86 percent.
