GPS and Inertial Measurement Unit (IMU) as a Navigation System for the Visually Impaired
GPS AND INERTIALMEASUREMENT UNIT AS A NAVIGATION SYSTEM ICCHP 2012 FOR THE VISUALLY IMPAIRED Author s: Jesus ZEGARRA René FARCY Laborator y Aimé Cotton ( France)
OBJECTIVES-To develop a device which can give to the visuallyimpaired the possibility to navigate to new placesin the cities; as a consequence, give a betterquality of life.- To provide the instantaneous direction of theblind person even if stopped-To compensate GPS echoes and magnetic fieldperturbations in urban areas- Show the advantages and limitations of the wholesystem relatively to standard GPS devices.
PROBLEMS GPS signal deficiencies (SIRF 3 - last generation): do not give a right heading when they are in the cities (hard reception conditions). Real way urban environment Antenne GPS SIRF 3 GPS Smart Phone Samsung OMNIA GPS SIRF 3
PROBLEMS The GPS devices do not give the right heading when the user does not move (It is necessary a minimum of speed for updating the heading) 15 Km/h in average for having a right heading Basic solution : the use of one IMU for giving the right heading in magnetic field perturbation conditions. Objective: To update a correct heading every second for a speed less than 15km/h.
HOW TO GIVE THE VOCAL INFORMATION TO THE NEXT POINT? The unit system is : - meters for the distances - time dial for the directions i.e. : from 1 o’clock to 12 o’clock with one hour of precision for instance, “12 o’clock, 40 meters” means go straight, 40 meters, “9 o’clock, 90 meters” means turning left and walk 90 meters
INFORMATION TO THE NEXT POINT For improving the information-We have done extra information about the next point « Way to»:-For instance:<<Way to 2 hours>>, means that the next point n+ 1 turn to theright taking into consideration the orientation of the person - -
SOLUTION Use of an IMU (Inertial Measurement Unit), developed in the laboratory containing : a 3 axis accelerometer, a 1 axis gyroscope, a 3 axis compass and a module Bluetooth transmitter to merge information with the GPS. The device is placed on the right side of the person. GPS IMU
MAIN DESIGN Module 3 axis Bluetoothcompass Filter sensor Rx- Tx Bluetooth Internet 1 axis Smart Filtergyroscope dsPic Phone 3 axisaccelerometer Filter GPS sensor
HOW TO USE THE DEVICE? There are three ways of saving the GPS coordinates (latitude and longitude) of the destination point. Saving using the GPS antenna –used in the Navigation Window Saving the coordinates by writing the adress of the destination Saving the coordinates by writing directly the coordinates GPS Keyboard 12 bottons Window
NAVIGATION WINDOW-BRAILLE SYSTEM Chosing the point Boutton for saving of destination the current coordinates GPS Close the Navigation window The user can chose the points around him between 2km, 5 km and all the points closer to him Heading and Information about distance to the the current adress point of destination
TESTS ABOUT THE USE OF THE WHOLE SYSTEM-The tests were conducted in Paris in thethirteenth, fourteenth and tenth neighborhoodin bad GPS reception conditions : high buildingsin small streets and bad magnetic conditions :walking along the Senna river (electricalcables), crossing metallic bridges, etc.-Six points of destination were chosen (thedistance between the destination can vary from3 to 5 km). Ten visually impaired people testedthe system (in category 3, 4 and 5 according tothe World Heath Organization) .-
RESULTS All the subjects arrived to the destination points alone (except one who was not confident enough after training to make the tests). The benefits about the use of GPS seem to be proportional to the initial autonomy of the visually impaired. Teaching the way of using the device is faster for the subjects in category 3 than for those in category 4 and 5. The main problem is keeping the security for the user that suddenly increased his autonomy in unknown environments. The risk was the same for the three categories.
CONCLUSIONS The GPS system coupled to IMU is better because the heading is more stable in the pedestrian navigation and, the person does not have to walk for knowing the direction to go. The information about heading and distance is important because it lends us to arrive to the final destination with only the coordinates GPS of the final destination . It also works even when the cartography of the place is not well elaborated because the person can take any direction and the system can guide him until the destination . It seems to be one reliable guiding system option for the blind people in the cities . Good autonomy of the whole system (6 hours enough for arriving one destination of 7 km)