Tongue drive system


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Tongue drive system

  1. 1. TONGUE DRIVE SYSTEM Presented by: Anagha Balakrishnan ER & DCI-IT,Vellayambalam RollNo: 07
  2. 2. What is TDS?TONGUE–OPERATED assistive technology for people with severe disability to control their environmentDEVELPOED by GT Bionics Lab
  3. 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. 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. 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. 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. 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. 8.  Head control•WHEELCHAIR controlled byhead control device•NOT good for theusers with bad head movementability
  9. 9. Why Tongue?...
  10. 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. 11. TDS – Overview
  12. 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. 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. 14. TDS Prototypes
  15. 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. 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. 17.  CONTROL unit & reference compass hidden under face shield cap ENTIRE system was powered by a 3.3V coin-sized battery(CR2023)
  18. 18.  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
  19. 19. 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
  20. 20. • TOTAL of 12 samples (3 per sensor)are recorded in 12-variable vectors• THE PCA-based feature-extractionalgorithm calculates the eigenvectors and Eigen valuesbased on the 12-variable vectors• THREE eigenvectors with the largestEigen values are then chosen to set up the featurematrix [v1, v2, v3]
  21. 21. • BY multiplying the training vectorswith the feature matrix, the SSP algorithm forms acluster (class) of 10 data points from training for eachspecific command•TESTING: k-nearest neighbour (kNN) classifier is thenused in real time to evaluate the proximity of theincoming data points to the clusters formed earlier inthe training phase
  22. 22. • kNN starts at the incoming new data pointand inflates an imaginary sphere around that data pointuntil it contains a certain number (k) of the nearesttraining data points• IT associates the new data point to thecommand that has the majority of the training datapoints inside that spherical region.
  23. 23. AFTER finding the intended user command,the mouse pointer starts moving slowly in the selecteddirection FOR faster access the user can hold his orher tongue in the position of the issued command andthe pointer will gradually accelerate until it reaches acertain maximum velocity
  24. 24. 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
  25. 25.  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.
  26. 26. Implementation - Controlling a PoweredWheel Chair
  27. 27. Block diagram & hardware component SYSTEM consists of the hall effect sensors (A1231), MSP430 microcontroller, H-Bridge driver (SN754410)
  28. 28.  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
  29. 29.  SENSOR- Linear Bipolar Hall effect sensor TRANSDUCER which varies its output voltage inresponse to changes in magnetic field•VOLTAGE:4.5V-5.5V•OUTPUT is an analogvoltage that vary from 0-5V•THAT is converted to adigital value by ADC
  30. 30.  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
  31. 31. •4 SWITCHES•WHEN A and D are closed, apositive voltage applied across themotor•WHEN B and C are closed , voltageis reversed, allowing reverse operationof the motor
  32. 32.  DC Motors and Gear Box•5V DC motors with a gearbox for drivingthe vehicle•USED 2 motors: Left and right•LEFT motor at rest and right in motionturn vehicle left and vice versa•FOR forward and backward motion boththe motors are driven in same directionwith same speed
  33. 33. 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
  34. 34.  Pulse Width Modulation •MODULATING technique which generates variable width pulses is used to vary the speed of the motor
  35. 35.  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
  36. 36.  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
  37. 37.  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
  38. 38. Advantages SIMPLE to implement , low cost, easy to operate flexible NO surgery needed OFFERS better privacy to the user
  39. 39. Drawbacks USERS should avoid inserting ferromagnetic objects in their mouth MAGNETIC tracer should be removed if the user is undergoing MRI