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Transcript of SOUND SOURCE LOCALIZATION 2017-06-07¢  ¢â‚¬¢Sound source...

  • SOUND SOURCE LOCALIZATION SIS PROJECT – EPFL BA6

    Marco Vieira Ruas, Clara Barret & Nathalie Camplani

    Supervisor Bahar Haghighat

    Professor Alcheiro Martinoli

  • E-PUCKS

    • Invented by EPFL in 2004 (first edition) and performed until 2006 (third edition)

    • A robot Designed for Education in Engineering

    • Equipped with sensors  interaction with the environment

  • BASIC THEORY

    • Sound source localization using a “sound source” and a “searcher”

    • “searcher” receives the signal at its microphones with different phases  𝑝 𝑑, 𝑡 = 𝐴0 cos(𝑘𝑑 − 𝜔𝑡 + 𝜑)

  • METHODS STEP 1

    Analysis of the signal

    STEP 2 Determination of 𝜑

    and cos 𝜃

    STEP 3 Turn to the right

    direction

    STEP 4 Stop rotation

    STEP 5 Go forward

    STEP 6 Goal

    reached

  • • FFT (already given)  looking for the maximum peak

    • Obtain the corresponding coefficients  𝐹𝑖 = 𝐴𝑖 2 + 𝐵𝑖

    2

    • Maximal frequency: 𝑓𝑝𝑒𝑎𝑘 = 𝑓𝑠∙𝑖

    3∙𝐿

    STEP 1 Analysis of the signal

    Property Webots E-pucks

    Sampling frequency [Hz] 33’000 16’384

    Signal length [-] 128 256

    Index of maximum magnitude (FFT) [-] 4 15 or 7

  • • Phase for each microphone: 𝜑 = tan−1 −𝐵𝑖/𝐴𝑖

    • Time shifts: ∆𝑇 = ∆𝜑

    𝜔 =

    ∆𝜑

    2𝜋∙𝑓𝑝𝑒𝑎𝑘

    • cos 𝜃 = 𝑐∙∆𝑇

    𝑑

    STEP 2 Determination of 𝜑

    and cos 𝜃

  • • Based on ∆𝜑21 − ∆𝜑20

    • Webots

    • E-pucks  not as expected

    • Definition of the boundaries after trials

    • ∆𝜑21 − ∆𝜑20 < −0.2 turn clockwise

    • ∆𝜑21 − ∆𝜑20 > 0.2 turn counter clockwise

    STEP 3 Turn to the right

    direction

  • Webots

    • Is in front when: cos 𝜃01 < 0.15

    STEP 4 Stop rotation

    E-pucks

    If −0.2 < ∆𝜑21 − ∆𝜑20 < 0.2

    • When 0 < cos 𝜃12 < 4  e-puck is in front of the

    «sound source» : can go straight

    • When cos 𝜃12 > 4 or cos 𝜃12 < 0  e-puck is behind the «sound source» :

    before going forward it has to make a turn of 180°

    STEP 5 Go forward

  • • Use IR sensors

    • Webots: 𝐼𝑅0 or 𝐼𝑅1 > 200

    • E-pucks: less sensible, use also the 𝐼𝑅6 and 𝐼𝑅7

    STEP 6 Goal

    reached

  • DIFFICULTIES

    • E-pucks sensible to noises and limitations of memory

    • Frequencies recorded by the e-puck don’t have a constant index of the maximum peak • Chose the most common one

    • Wheels change the sound characteristics • Again look at the real values recorded

    • Too far from “sound source”, “searcher” recorded only NaN values • Implementation of a new condition: U-turn and go forward

  • DEMONSTRATION: WEBOTS

  • DEMONSTRATION: E-PUCKS «Sound source» «Searcher»

    ← ↓

    15 cm 30 cm

    «Sound source» «Searcher»

    ↓ →

    15 cm 30 cm

  • REFERENCES

    • SR, SIS Project, Project: E-puck sound source localization, Distributed Intelligent Systems and Algorithms Laboratory, EPFL, accessed on April 2017.

    • Xavier Raemy, Introduction to the e-puck robot, SWIS group, EPFL, Lausanne, 28 november 2006, project web page: http://www.e-puck.org.

    • Alcherio Martinoli, Signals, Instrumental and System, Course for SIE BA6, EPFL, Lausanne, 2017.

    • EPFL, e-puck education robot, http://www.e-puck.org., consulted the 28.05.2017.

    THANK YOU, QUESTIONS?