Acoustic Navigation for Mobile Robots

Computer System DesignSpring 2003

Current Status

• We are currently conducting breadboard testing and circuit analysis with individual subcomponents of the design

• We are on schedule but are beginning to run into some unexpected problems.

Current Design

Deviations from Proposal

• Addition of an adjustable filter controlled by a microcontroller

• Switched microphone sampling control to microprocessor

• Now have 8 frequency bands to select from• Went from a 4-bit to an 8-bit A/D

Microphone Array

• Separate PCB for increased modularity and function

• Implementing Plexiglass frame for Sound Dampening and increased directionality.

• Have created the circuit/pcb design in Eagle 4.0, currently investigating etching facilities.

Signal Rectification

Adjustable Filter Addition

• Dual Switched Capacitor Filter• In conjunction with an oscillator, counters,

and a multiplexor, design offers multiple frequencies to be polled at the microprocessors request.

• Allows for more variability of the sensor system for future expansion into the communications realm.

Ideal Transfer FunctionBode Plot of Ideal Transfer Functionof National Semiconductor LMF100

High Performance Dual Switched Capacitor FilterQ = 3

0

0.2

0.4

0.6

0.8

1

1.2

1 10 100 1000 10000 100000

Frequency (Hz)

Gai

n (V

/V)

Newly Encountered Problems

• Oscillator causes drastic noise leaving the microphone signal to be almost indistinguishable

• Have not been able to get the filter to function as expected

• Original Panasonic microphones do not react to sound sources at distances much greater than 6-12 inches

Possible Solutions

• Working filter ought to clean up the microphone signal noise caused by oscillator

• Plan to preamplify the microphone signals for better sensitivity

Schedule