Using an Electromagnetic and Acoustic Sensing Device to Determine Direction and Range Part of the Intelligent Ground Vehicle Project Maria 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 TIME t Elapsed = 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 < MAX 700<R< MAX ROBOT TURNS 300 < L < < R < 700 L = R 0 < L < < 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