1. TONGUE DRIVE SYSTEM
Presented by:
Anagha Balakrishnan
ER & DCI-IT,Vellayambalam
RollNo: 07

2. What is TDS?
TONGUE–OPERATED assistive technology for
people with severe disability to control
their environment
DEVELPOED by GT Bionics Lab

3. 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.

4. 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

5. Cause of Spinal Cord Injury…
 SPINAL CORD
PARALYSIS is squashed or blood circulation of
the spinal cord is cut off, which will result in..
UNABLE to easy breath
UNABLE to feel pain or sensation
SORES on skin not being able to move around
SEXUAL dysfunction

6. 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

7.  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

8.  Head control
•WHEELCHAIR controlled by
head control device
•NOT good for the
users with bad head movement
ability

9. Why Tongue?...

10.  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

11. TDS – Overview

12. 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

13.  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

14. TDS Prototypes

15.  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

16.  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

17.  CONTROL unit & reference compass hidden under face
shield cap
 ENTIRE system was powered by a 3.3V coin-sized
battery(CR2023)

19.  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

20. 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

21. • 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]

22. • 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

23. • 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.

24. 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

25. 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

26.  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.

27. Implementation
- Controlling a Powered
Wheel Chair

30. Block diagram & hardware component
 SYSTEM consists of the hall effect sensors (A1231),
MSP430 microcontroller, H-Bridge driver (SN754410)

31.  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

32.  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

33.  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

34. •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

35.  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

36. 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

38.  Pulse Width Modulation
•MODULATING technique which generates variable width
pulses is used to vary the speed of the motor

39.  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

41.  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

42.  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

43. Advantages
 SIMPLE to implement , low cost, easy to operate
flexible
 NO surgery needed
 OFFERS better privacy to the user

44. Drawbacks
 USERS should avoid inserting ferromagnetic objects in
their mouth
 MAGNETIC tracer should be removed if the user is
undergoing MRI

46. QUESTION TIME