Acoustic Navigation for Mobile Robots Computer System Design Spring 2003

Background  Microphone arrays have been in use for over 30 years.  Array can outperform even the best directional microphones.  Digital conversion increases possibilities of realistic implementations.  Applicable in conference rooms/auditoriums, concerts, surveillance equipment and robotic designs.  Rutgers University developed 380 microphone array system proving the usefulness of this technique.

Problem Statement  Design an acoustic navigation module with the ability to detect sound in a 360°environment using a microphone array that will allow a mobile robot to perform movement based on sound location.

Design Objective  Develop a printed circuit board interface for the microphone array  Design acoustic fixtures to increase directionality of microphones  Develop algorithms to determine the angle and position of the transmitted sound  Design must be able to detect certain frequency ranges in which the robot will respond differently based on the frequency received.

Existing Solutions Phonotaxis – University of Stirling, Scotland  4 microphone array to model female crickets homing in on the sound of a male cricket Signal Rectifier – Elliott Sound Products  Developed an LED audio VU meter that uses simple full-wave rectifier and pre-amplifier hardware circuitry

Existing Solutions (con’t) Convict Episcopal de Luxembourg, Bouyette Group Sound Sensor  Sound sensor that measures the difference in phase of two audio signals to determine the source of the sound  Robot searches for and advances toward pulsing sounds Audio Frequency Sensor  A single microphone implementation that measures the pulses of the audio signal to determine the frequency

Microphone Array  Implementing 8 microphones, allowing each microphone 45° of coverage.  Electret microphones – best compromise between response, cost, and ease of design.  To increase directionality, we will implement a sound dampening system.

Proposed Hardware Design  Interface the Coldfire 8-bit UART  4-bit Signal Resolution  3-bit representation of selected microphone  1-bit to represent filter type  Each microphone polled sequentially  Clock and counter to perform polling

Proposed Design Diagram

Design Constraints  Cost  Size/Weight  Compatibility  Power  Sound Frequency Range  Environment  Robot Mobility  Single Tone Testing  Time

Alternative Solutions  Finding single largest amplitude  Analog comparison and digital comparison  Digital Signal Processing  Beamforming  Time and amplitude differential

Design Validation

Economic Analysis

Societal, Safety, and Environmental Analysis  Electronics in society  Manufacturing process chemicals  Capacitor, resistors, integrated circuit proper usage  Water hazards  Proper power and ground sources

Management  Trent Foley  Lead hardware design engineer, documentation.  Josh Earley  Development of mic array, acoustic directionality, board design.  Chris Gonzales  Software design, budget, procurement of parts.  Thomas Garner  Lead software engineer, board design.

Scheduling  M  6:15 p.m. (meeting with advisors)  M-W-F  1:30 p.m. - 4:00 p.m. (regular design meetings)  Weekends  open (when necessary)