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 withsevere 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 severelydisabled 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 environment, 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 active, 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 Driveconsists 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 headset 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 processed to extract the user’s commands. The user can then use these commands to access a desktop 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 durations 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 wirelessly 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 signals 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 functions 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 controller unit are demodulated and DE multiplexed to extract the individual sensor outputs. 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 software 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 moreexperiencedusers. 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
Allows disabled people to power a wheelchair
Allows disabled people to use a computer
.Allows disabled people to not depend on others
Allows disabled people to have more freedom
Allows disabled people to become employable
DRAWBACKS
Computer battery could die when not around charger
Could take a while to learn how to use it
Might not be affordable for some people
Decreases job opportunities for some
Computer could go down
CONCLUSION
Tongue drive system technology is a gift for the physically challenged and disabled persons to lead their life equal to the normal persons in the society. A tongue operated magnetic sensor 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 existing 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 custom designed low-power electronics that entirely fit within the mouthpiece is currently under development.
REFERENCES
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