Ultrasonic path guidance for visually impaired

Details Ultrasonic path guidance for visually impaired Ultrasonic path guidance for visually impaired

2002-05-31

2003-12-30

Pihulic, Daniel T. (Department: 3662)

Communications, electrical: acoustic wave systems and devices

Echo systems

Distance or direction finding

Reexamination Certificate

active

06671226

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a system and method for providing visually impaired individuals and more particularly to a system and method of emitting ultrasound pulses to detect obstacles in the path of the visually impaired.
BACKGROUND OF THE INVENTION
Based on census data from the 1990 census, the mean monthly earnings for those without disabilities has been reported as $1,962. For the severe and non-severe “functional limitation in seeing” group, the mean monthly earnings was reported as $1,573. For the severe “functional limitation in seeing” group only, the mean monthly earning was $1,238. When these numbers are calculated for a mean yearly income, the no disability work force made $23,544, the severe and non-severe limitation in seeing group made $18,876, and the severe limitations only group made $14,856. The difference in mean earnings is alarming. The visually impaired were not only unable to compete for jobs, they were unable to compete for jobs with high earnings.
Any device or technique that enables the visually impaired to move more easily in their surroundings would be of benefit. The most familiar aids are, of course, the cane and the guide dog. The cane does not alert the visually impaired to obstacles they are approaching that are beyond the reach of the cane, nor to those located above ground level, like an overhanging branch, for example. A guide dog may stop the individual from proceeding, but does not provide feedback as to obstacles in the path of the individual. In any event, neither the cane nor the guide dog is as unobtrusive as may sometimes be desired. Neither the cane nor the guide dog permits the visually impaired to navigate with both hands free.
A U.S. patent to Nelkin, Pat. No. 3,337,839 describes a guidance apparatus that uses a plurality of ultrasound transducers in an array worn by a visually impaired person. The transducers are directional and are pointed into separate locations in front of the individual. Echoes of the ultrasound pulses from the transducers are identified on the basis of time of receipt and are used to stimulate an array of vibratory devices also worn by the user. The vibratory devices mimic the locations of the ultrasonic transducers to indicate where, in front of the user, an obstacle may be encountered.
Elchinger U.S. Pat. No. 4,280,204 dated Jul. 21, 1981 describes a modified mobility cane for the visually impaired. It is described as capable of chest and/or face height detection at multiple distances. The transducer is ultrasonic and is mounted on the cane. The output is auditory, sent by wire to an earphone. The design is advantageous to the extent that it allows the user to have one free hand. It also is described as having a short range and a long range option for detecting chest height obstacles or face height obstacles. The zone of detection is described as being adjustable. The design is disadvantageous because the output is through an earphone, which could be uncomfortable and impede the visually impaired user's ability to hear. The user does not have both hands free. The single transducer does not appear to provide sufficient information as to location of an obstacle being approached.
U.S. Pat. No. 4,459,689 of Biber dated Jul. 10, 1984 is for a multiple zone object detection system. This system uses ultrasonic sensors to detect multiple environmental zones. Like the Nelkin patent, Biber distinguishes between each zone on the basis of the time of receipt of echoes of the serially transmitted ultrasound signals. The Biber patent does not refer to guidance for the visually impaired.
Two U.S. Pat. Nos. 4,658,385 and 4,636,996, both to Tsuji, describe an ultrasonic obstacle detection system and methodology using a CPU for mobile robot control. The system uses three transmitters, two receivers, a CPU and data ROMs. It calculates the location of an obstacle with spatial coordinates and the time difference between wave transmission and reception. The timing of echoes received at the two receivers is used to specify location coordinates of obstacles.
Vanmoor U.S. Pat. No. 5,982,286, issued Nov. 9, 1999, is for another electronic travel aid for the visually impaired. The frame of a pair of eyeglasses houses the sensors, circuitry and power source. The output is auditory. A benefit is that the system must always be worn in the same way, insuring proper sensor placement. As the wearer moves closer to an obstacle a beeping output becomes louder and more frequent. The patent does not describe any output indication of location other than distance from the wearer. The audible outputs are by the individual's ears, which can interfere with the user's hearing.
In 1970, Geoff Mowatt, created a sensor that, when it detected an obstacle, a vibratory output would stimulate its user's hand. As the distance to an obstacle decreased, the frequency of vibration increased. This device had an adjustable detection range for short distance (3′) and long distance (12′). The Mowatt sensor is believed to have been commercially the most successful electronic travel aid (ETA) thus far. It had roughly 30 years of commercial availability.
In 1971, the United States Veterans Administration evaluated the C-4 Laser Cane to be used by blind veterans. One of the veterans in the evaluation program wrote, “it was designed to detect obstacles hanging overhead or protruding from the sides at head level within the path of travel; to detect objects in front and between the left and right arc; and to detect such downdrops as deep curbs, stairways, and from platforms.” The advantage of the Laser Cane is that is was a primary aid that could detect all obstacles in front of its user. This was also one of the major disadvantages. A complex electronic device, such as the Laser Cane, consumes power and runs out of power. The user may end up stranded. Another disadvantage is the extensive amount of training required to be proficient with the Laser Cane. The veteran who used the device went through five weeks of intense training. Few people with full time employment can afford to take such time away from their jobs. A further disadvantage is cost. Complex devices like the Laser Cane are expensive to manufacture and are built with expensive state-of-the-art sensing equipment. Few visually impaired people are in the position to take the time and spend the money to use the Laser Cane.
The newest generation of electronic travel aids (ETAs) is far more sophisticated than previous generations, thanks to the microprocessor. A research team at the University of Michigan developed an ETA called the “GuideCane.” It is an enhanced seeing-eye cane that uses an array of ultrasonic sensors to detect obstacles in its user's path. The sensors and processor circuitry are at the front end of the cane, attached to two large wheels. The user chooses the direction of travel by using ajoystick attached to the cane's handle. This propels the cane and user in the desired direction. When an obstacle is detected, the GuideCane measures the distance and orientation to the obstacle and steers the user around. Unfortunately, the design of the GuideCane system warrants some questions about user safety. It is not clear how well the GuideCane handles floor obstacles, such as curbs and steps. There is a strong possibility of injury to the user or other people when navigating through crowded places. The system guides the user past detected obstacles, but if someone or something moves between the user and the sensory equipment (i.e., a closing door or a hurried pedestrian), the user or intervening person could sustain injuries. It is not clear whether or how chest and face height obstacles are detected. Once again cost is believed to be a drawback.
Another new ETA, the Navbelt, uses a belt of ultrasonic sensors to create a complete environmental map of its wearer's surrounding environment. The technology is based on real-time signal processing optimized to solve for obstacle avoidance. Eventually, it could be combined with global posi

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