7TONGUE DRIVE SYSTEM

Presented by:

Anagha Balakrishnan

ER & DCI-IT,Vellayambalam

RollNo: 07

What is TDS?

TONGUE–OPERATED assistive

technology for people with severe

disability to control their

environment

DEVELPOED by GT Bionics Lab

Assistive Technology ?

ASSISTIVE TECHNOLOGY is an umbrella term

that includes assistive, adaptive, and

rehabilitative devices for people with

disabilities and also includes the process

used in selecting, locating, and using

them.

Why Spinal Cord Injury is Fatal?

•SPINAL CORD is located

inside the spine

•CONNECTS the brain to

nerves in the body

•MESSAGE travel in very high

speed from brain to rest of

the body

Cause of Spinal Cord Injury…

SPINAL CORD is squashed or blood

circulation of the spinal cord is cut off,

which will result in..

PARALYSIS

UNABLE to easy breath

UNABLE to feel pain or sensation

SORES on skin not being able to move around

SEXUAL dysfunction

Existing Assistive Technologies…

Sip-and-Puff wheel chair

•USE air pressure to

control wheel chair by

sipping and puffing

•NOT good for people

with week breathing

Voice activated powered wheelchair

•WHEN user speaks

commands, a

microphone in a throat

detects the vibration of

vocal cord

•UNSTABLE for powered

wheelchair control in

noisy

environments

Head control

•WHEELCHAIR

controlled by head

control device

•NOT good for the

users with bad head

movement ability

Why Tongue?...

TONGUE and mouth occupies the major part

MUSCLE fibers in tongue is similar to heart muscle

fibers

LOW rate of Perceived Exertion

DIRECTLY connected to the brain

HIDDEN inside mouth will give a certain degree of

privacy

TDS – Overview

TDS –Overview…

SMALL permanent magnet pierced on the tongue

ARRAY of Hall-effect magnetic sensors senses the magnetic field

SENSORS mounted on a dental retainer and attached on the outside of the teeth

SMALL batteries are intended to power

POWER management circuitry scans through the sensors and turn on one at a time

TDM analog output are digitized, modulated and transmitted to the external control unit through a wireless link

FROM their signals are demodulated, demultiplexed to extract individual sensor output

BY processing these output command is identified

TDS Prototypes

BUILD on a face shield

FUNCTION is to directly emulate mouse

pointing and selection function with the

tongue movement

SIX COMMANDS : up, down, right, left,

single click & double click

SSP algorithm running in background

MAGNETIC TRACER : small, cylindrical,

rare-earth permanent magnet

PAIR of two-axis magnetic field sensor

modules- each contained a pair of

orthogonal magneto-inductive sensor

THREE AXIS MODULE: used as a reference

electronic compass to minimize the effect

of external magnetic field interference

CONTROL unit & reference compass

hidden under face shield cap

ENTIRE system was powered by a 3.3V

coin-sized battery(CR2023)

SENSOR output where send serially to the

ultralow-power MSP430 microcontroller

MICROCONTROLLER took 11 samples from

each sensor

SAMPLES are arranged in a data frame

and wirelessly transmitted to a PC across

a 2.4 GHz wireless link established

between nRF2401 transceivers

Sensor Signal Processing algorithm DEVELOPED in MATLAB environments

2 phases: Training & Testing

•TRAINING : USES principal components

analysis

(PCA) to extract the most important

features of the sensor output waveforms

for each specific command

• USER repeats each of the

six designated commands 10 times in 3-

second intervals

• TOTAL of 12 samples

(3 per sensor) are recorded in 12-

variable vectors

• THE PCA-based

feature-extraction algorithm calculates

the eigenvectors and Eigen values based

on the 12-variable vectors

• THREE eigenvectors

with the largest Eigen values are then

chosen to set up the feature matrix [v1,

v2, v3]

• BY multiplying the

training vectors with the feature matrix,

the SSP algorithm forms a cluster (class)

of 10 data points from training for each

specific command

•TESTING: k-nearest neighbour (kNN)

classifier is then used in real time to

evaluate the proximity of the incoming

data points to the clusters formed earlier

in the training phase

• kNN starts at the incoming new

data point and inflates an imaginary

sphere around that data point until it

contains a certain number (k) of the

nearest training data points

• IT associates the new data point

to the command that has the majority of

the training data points inside that

spherical region.

AFTER finding the intended user

command, the mouse pointer starts

moving slowly in the selected direction

FOR faster access the user can

hold his or her tongue in the position of

the issued command and the pointer will

gradually accelerate until it reaches a

certain maximum velocity

Training Session

GRAPHICAL user interface (GUI) prompted

the user to define each command by moving

his tongue from its resting position to the

corresponding command position when the

command light was on and returning it back

to the resting position when the light went

off

THIS procedure was repeated 10 times for

the entire set of six commands plus the

tongue resting position, resulting in a

total of 70 training data points.

Implementation

- Controlling a Powered Wheel Chair

SYSTEM consists of the hall effect sensors

(A1231),

MSP430 microcontroller, H-Bridge driver

(SN754410)

Block diagram & hardware component

4 ADC channels of MSP430 convert analog

signals from sensors to digital for

processing

BASED on the processed information

microcontroller drives the driver IC

DRIVER IC drives the DC powered

wheelchair

SENSOR- Linear Bipolar Hall effect sensor

TRANSDUCER which varies its output

voltage in response to changes in magnetic field

•VOLTAGE:4.5V-5.5V

•OUTPUT is an analog

voltage that vary

from 0-5V

•THAT is converted to

a digital value by ADC

H-BRIDGE DRIVER : used to drive the

wheelchair

SN7454410:BidirectionalH-Bridge driver

5V power supply is given

SPEED of the wheelchair is controlled by the

PWM signals from MSP430

•4 SWITCHES

•WHEN A and D are closed,

a positive voltage applied

across the motor

•WHEN B and C are closed ,

voltage is reversed,

allowing reverse operation

of the motor

DC Motors and Gear Box•5V DC motors with a gearbox

for driving the vehicle

•USED 2 motors: Left and right

•LEFT motor at rest and right

in motion turn vehicle left and

vice versa

•FOR forward and backward

motion both the motors are

driven in same direction with

same speed

Software Components

ADC10(Analog to Digital converter)

•MSP430G2252 has 8 ADC channels of 10 bit each

•ADC10 convert the analog signal from the sensor

into digital value

•WE get the value ranging from 0-1023

Pulse Width Modulation

•MODULATING technique which generates

variable width pulses is used to vary the

speed of the motor

Algorithm

•ROUND ROBIN algorithm that implements

polling technique

•SENSOR values are always read one after

other in a continuous loop

•FEW threshold values set for each sensor

•IF reading from sensors reaches the threshold

value program triggers the change of state

S1 & S2 front sensor , S3 & S4 back sensors

WHITE circle in the middle- resting position of

tongue

DIFFERENT flag values for each sensor

IF sensor is high, then the flag value remains high

until the operation is performed, then it is reset

again

f1 - S1 > 750 // forward

f2 - S2 > 600 // backward

f3 - S3 > 700 // speed increase

f4 - S4 > 700 // speed decrease

f5 - S1 > 600 & S3 > 600 // turn left

f6 - S2 > 600 & S4 > 600 // turn right

Advantages SIMPLE to implement , low cost, easy to

operate flexible

NO surgery needed

OFFERS better privacy to the user

Drawbacks

USERS should avoid inserting

ferromagnetic objects in their mouth

MAGNETIC tracer should be removed

if the user is undergoing MRI

CONCLUSI

ON

QU

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