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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?