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Acoustic Navigation for Mobile
Robots
Computer System Design
Spring 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 Function
Bode Plot of Ideal Transfer Function
of National Semiconductor LMF100
High Performance Dual Switched Capacitor Filter
Q=3
1.2
Gain (V/V)
1
0.8
0.6
0.4
0.2
0
1
10
100
1000
Frequency (Hz)
10000
100000
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