ABSTRACT

A new assistive technology developed by engineers at the Georgia Institute of

Technology. It helps individuals with severe disabilities

lead more independent lives. The individual with disabilities such as to operate a computer

control a powered wheelchair and Interact with their environments simply by moving their

tongues. The "Tongue Drive" system is a tongue-operated assistive technology developed for

people with severe disability to control their environment. The tongue is considered an excellent

appendagein severely disabled people for operating an assistive device.

INTRODUCTION

Assistive technologies are critical for people with severe disabilities to lead a self-supportive

independent life Persons severely disabled as a result of causes ranging from traumatic brain and

spinal cord injuries to stroke generally find it extremely difficult to carry out everyday tasks

without continuous help. Assistive

Technologies that would help them communicate their intentions and effectively control their en-

vironment, especially to operate a computer, would greatly improve the quality of life for this

group of people and may even help them to be employed.

This device could revolutionize the field of assistive technologies by helping individuals

with severe disabilities, such as those with high-level spinal cord injuries, return to rich and ac -

tive, independent and productive lives. The TDS provides people with minimal or no movement

ability in their upper limbs with an efficacious tool for computer access and environmental

Control. Tongue Drive consists of A small permanent magnet secured on the tongue by

implantation, piercing, or tissue adhesives is used as a tracer, the

movement of which is detected by an array of magnetic field sensors mounted on a head-

set outside the mouth or on an orthodontic brace inside. The sensor outputs signals are wirelessly

transmitted to an ultraportable computer carried on the user’s clothing or wheelchair and are pro-

cessed to extract the user’s commands. The user can then use these commands to access a desk-

top computer, control a power wheelchair, or interact with his or her environment.

Use of Tongue for Manipulation

TDS chose the tongue to operate the system

because unlike hands and feet, which are controlled

by the brain through the spinal cord, the tongue is directly connected to the brain by a cranial

nerve that generally escapes damage in severe spinal cord injuries or neuromuscular diseases.

Tongue movements are also fast, accurate and do not require much thinking, concentration or

effort. Movement of the magnetic tracer attached to the tongue is detected by an array of

magnetic field sensors mounted on a headset outside the mouth or on an orthodontic brace inside

the mouth. The sensor output signals are wirelessly transmitted to a portable computer, which

can be carried on the user's clothing or wheelchair

TDS PROCES

.In Tongue Drive system, the motion of the tongue is traced by an array of Hall-effect magnetic

sensors, which measure the magnetic field generated by a small permanent magnet that is

contained within a nonmagnetic fixture and pierced on the tongue. The magnetic sensors are

mounted on a dental retainer and attached on the outside of the teeth to measure the magnetic

field from different angles and provide continuous analog outputs.

Fig. 1 shows the Tongue Drive System block diagram with two major units: one inside the

mouth, the mouthpiece, and the other outside, a portable body worn controller. Small batteries

such as hearing aid button-sized cells are intended to power the mouthpiece for extended dura-

tions up to a mouth. The power management circuitry scans through the sensors and turns them

on one at a time to save power. The time division multiplexes (TDM) analog outputs are then

digitized, modulated, and transmitted to the external controller unit across a wireless link. The

magnetic field generated by the tracer inside and around the mouth varies as a result of the

tongue movements. These variations are detected by an array of sensitive magnetic sensors

mounted on a headset outside the mouth, similar to a head-worn microphone, or mounted on a

dental retainer inside the mouth, similar to an orthodontic brace. The sensor outputs are wire-

lessly transmitted to a personal digital assistant (PDA) also worn by the user.

A sensor signal processing (SSP) algorithm running on the PDA classifies the sensor sig-

nals and converts them into user control commands that are then wirelessly communicated to the

targeted devices in the user’s environment. The principal advantage of the TDS is that a few

magnetic sensors and a small magnetic tracer can potentially capture a large number of tongue

movements, each of which can represent a particular user command. A set of specific tongue

movements can be tailored for each individual user and mapped onto a set of customized func-

tions based on his or her abilities, oral

anatomy, personal preferences and lifestyle.

The user can also define a command to switch

the TDS to standby mode when he or she

wants to sleep, engage in a conversation, or

eat. The signals received by the external con-

troller unit are demodulated and DE multi-

plexed to extract the individual sensor out-

puts. By processing these outputs, the motion

of the permanent magnet and consequently the

tongue within the oral cavity is determined.

Assigning a certain control function to each

particular tongue movement is done in soft-

ware and can be easily customized control

functions may then individual user. These

customized control functions may then be

used to operate a variety of devices and

equipment including computers, phones, and

powered wheelchairs

PROTOTYPE TONGUE DRIVE SYSTEM

The system can potentially capture a large number of tongue movements, each of which

can represent a different user command. A unique set of specific tongue movements can be

tailored for each individual based on the user's abilities, oral anatomy, personal preferences and

lifestyle.

An individual could potentially train our system to recognize touching each tooth as a

different command. The ability to train our system with as many commands as an individual can

comfortably remember is a significant advantage over the common sip-n-puff device that acts as

a simple switch controlled by sucking or blowing through a straw.

The Tongue Drive system is also non-invasive and does not require brain surgery like some

of the brain-computer interface technologies.

TASKS PERFORMED IN TDS

Computer mouse tasks – left, right, up and down pointer movements and single-

and double-click. For each trial, the individual began by training the system. During the five-

minute training session, the individual repeated each of the six designated tongue movements 10

times.

During the testing session, the user moved his or her tongue to one of the predefined

command positions and the mouse pointer started moving in the selected direction. To move the

cursor faster, users could hold their tongue in the position of the issued command to gradually

accelerate the pointer until it reached a maximum velocity.

Results of the computer access test by novice users with the current Tongue Drive

prototype showed a response time of less than one second with almost 100 percent accuracy for

the six individual commands. This is equivalent to an information transfer rate of approximately

150 bits per minute, which is much faster than the bandwidth of most brain-computer

interfaces

The research team has also begun to develop software to connect the Tongue Drive

system to a wide variety of readily available communication tools such as text generators, speech

synthesizers and readers. In addition, the researchers plan to add control commands, such as

switching the system into standby mode to permit the user to eat, sleep or engage in a

conversation while extending battery life.

MODES IN POWERED WHEEL CHAIR

Operated the powered wheelchair using two different control strategies:

DISCRETE MODE

Discrete mode, designed for novice users, and continuous mode for more experienced users. In

discrete mode, if the user issued the command to move forward and then wanted to turn right, the

user would have to stop the wheelchair before issuing the command to turn right. The default

stop command was when the tongue returned to its resting position, bringing the wheelchair to a

standstill. Discrete mode is a safety feature particularly for novice users, but it reduces the agility

of the wheel chair movement.

CONTINUOUS MODE

In continuous mode, however, the user is allowed to steer the powered wheelchair to the left or

right as it is moving forward and backward, thus making it possible to follow a curve.”

ADVANTAGES OF TDS

Ø Allows disabled people to power a wheelchair

Ø Allows disabled people to use a computer

Ø .Allows disabled people to not depend on others

Ø Allows disabled people to have more freedom

Ø Allows disabled people to become employable

DRAWBACKS

Ø Computer battery could die when not around charger

Ø Could take a while to learn how to use it

Ø Might not be affordable for some people

Ø Decreases job opportunities for some

Ø Computer could go down

CONCLUSION

Tongue drive system technology is a gift for the physically challenged and disabled per-

sons to lead their life equal to the normal persons in the society. A tongue operated magnetic sen-

sor based wireless assistive technology has been developed for people with severe disabilities to

lead a self-supportive independent life enabling them to control their environment using their

tongue. This technology works by tracking movements of permanent magnet, secured on the

tongue, utilizing an array of linear Hall-effect sensors. The sensor outputs are a function of the

position-dependent magnetic field generated by the permanent magnet.

This allows a small array of sensors to capture a large number of tongue movements. Thus,

providing quicker, smoother, and more convenient proportional control compared to many exist-

ing assistive technologies. Other advantages of the Tongue Drive system are being unobtrusive,

low cost, minimally invasive, flexible, and easy to operate. A more advanced version with cus-

tom designed low-power electronics that entirely fit within the mouthpiece is currently under de-

velopment.

REFERENCES

1.http://www.sciencedaily.com/releases/2008/06/080630090821.html

2.http://www.infoniac.com

3. http://www.wired.com/wiredscience