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Mobility options for people who are blind

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10% of people considered legally blind also have mobility impairment, leading to reliance on others for mobility. Although there are limited specialty options available for blind people with mobility impairments, people have been successful using the current obstacle detection options like ultrasonic or infrared sensors.

A list of electronic travel aids for the blind can be accessed from the link below. These include different types of ultrasonic and infrared sensors, which provide users with an audio feedback with changing frequency and pitch according to the obstacles in the path. The range of a typical ultrasonic sensor is between 3-5 meters. These sensors can be either attached to the users cane or the wheelchair, depending on the user’s range of mobility. Other technology options include using GPS to provide direction.

Although the ultrasonic sensors seem to work well when traveling in the forward direction they do not provide the user any information about what is behind them making it difficult to back up or turn. A way of solving that problem would be to attach a sensor to the back of the wheelchair; a parking sensor similar to the one shown in the link below is used by some.

A specialty wheelchair is also being developed called the SPAM (Smart Power Assistance Module). The SPAM addresses some of the major concerns people with visual impairments have when using wheelchairs. SPAM uses multiple rangefinders, including both infrared and ultrasonic technology to detect obstacles. The hubs are modified to provide for a shorter stopping distance and the users are provided with a haptic feedback according to the proximity of obstacles. Preliminary tests showed positive results and the number of collisions were reduced for simple navigation tasks. However, the SPAM is still in the development stage.

In conclusion, the preferred option is using an ultrasonic or infrared sensor to extend the range of the cane to detect obstacles. Increasing the braking capability is also helpful along with a separate sensor to detect obstacles behind the user. Some additional useful links are also posted below.

Intermediate Seminar in Orientation and Mobility

Smith-Kettlewell Institute

The Bat K-Sonar

The Ultracane

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Author: Azeem Meuani
Affiliation: Georgia Institute of Technology