Using an Electromagnetic and Acoustic Sensing Device to

Determine Direction and Range Part of the Intelligent Ground

Vehicle ProjectMaria Pacana

Objective

• The implementation of an electromagnetic and acoustic sensing device that determines range and direction to enable one autonomous vehicle to follow another.

Sensing array:

• PIC-C microcontroller

• Radio transmitter

• Radio receiver

• Sonar transmitters and receivers

Sonar and Radio Transmitters

• Sonar and radio transmitted together

• Controlled by an LMC 555 CMOS

Timer at 1.66 Hz

• Rolling code radio transmitter, hard

to electronically ‘crack’.

The Radio And Sonar Receivers

• The sonar receiver must transmit in order to receive.

• When the radio receiver gets a signal, it initializes the sonar and enables it to receive.

The Radio and Sonar Recievers

•The sonar receiver must transmit in order to receive

•When the radio receiver gets a signal, it initializes the sonar and enables it to receive.

RADIO XMIT

ACOUSTIC XMIT

RADIO RCVR

BINAURAL SENSOR

TIMER

Diagram of Sensing Array

PIC -C

MCU

SPEED OF LIGHT

SPEED OF SOUND

. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

How It Works:

• The radio receiver gets the electromagnetic part of the signal at the speed of light.

• The sonar receiver gets the acoustic part of the signal at the speed of sound.

• The difference between the electromagnetic and acoustic signals indicates range.

• The difference between each ‘ear’ of the binaural receivers indicates direction.

RADIO RCVR

LEFT ‘EAR’

RIGHT ‘EAR’

T = 0

Diagram of the Signals

TIMEtElapsed = 20 ms

Navigation

• To test this system, the receivers were mounted on an autonomous mobile robot and connected to a PIC-C microcontroller.

• The robot takes the difference in readings between each ear of the binaural sonar receivers in order to correct itself.

• The greater the difference, the more the robot ‘corrects.’

START

RADIO ?

INIT COUNT

DELAY .5 ms

SET MAX = 1000

Y

N

700 <L < MAX700<R< MAX

ROBOT TURNS

300 < L < 700300 < R < 700

L = R

0 < L < 3000 < R < 300

GO FORWARD

N

STOP

N

GO FORWARD

Y

N

ROBOT CORRECTS

Advantages and Disadvantages

• Is not affected by sunlight

• Has more range, less resolution than IR

• The 400 V excitation pulse that switches the sonar on and off can cause electrical noise in other circuits

• ‘Echoes’ from the receiver

Thanks to:

• Professor Roman Kuc

• Ed Jackson

• The Intelligent Ground Vehicle Team