ERBOT1

built by Eduardo Robles

*
Target Environment Locomotion Method
Indoors 3 Wheels
Sensors / Input Devices Actuators / Output Devices
40 KHz IR proximity sensor
2 Polaroid sonar units
Dinsmore compass
2 modified servo motors
servo motor for sonar array
Control Method Power Source
Autonomous Battery
CPU Type Operating System
PIC Microcontroller None
Programming Lanuage Weight
C N/A
Time to build Cost to build
N/A N/A
URL for more information
http://www.erbots.com/
Comments
ERBOT1 is actually the test platform for some of the sensors and interfaces that will go into ERBOT2, a bigger project that is under construction nowdays.

ERBOT1 has an infrared "eye" that works on the principle of reflection of a 40 KHz modulated burst of IR light to detect any near obstacles in the robot path. It also has two "back to back" mounted sonars transducers (Polaroid), that can rotate 180 degrees to monitor long range obstacles. Movement of the sonars head is accomplished by a servo motor being driven to get the desired rotation. The information from the sonars is then used in the navigation desitions.

To help with navigation I also installed a Dinsmore compass in the very top of the robot, to avoid interference from the electromagnetical noise from the motors.

The Compass uses a 12C509 microcontroller that communicates via an I2C bus with the "master" microcontroller, a 16F628. All servos are controlled by a separate 16F84A that communicates with the master controller using RS232. The servo controller has the choice of spanning the servor 90 or 180 degrees, and can drive up to 8 servos simultaneously. It took a while to fine tune this, but it is working fine now.

All the programming for all controllers was done in C, using the HT-PICC compiler, a superb compiler.

The navigation algorithm is very simple and will be greatly improved in ERBOT2. For now, ERBOT1 looks for open spaces using the sonars and then uses the IR "eye" to avoid any obstacles. Whenever it finds a dead-pocket corner where the IR sensor doesn't help anymore, it then stops, activates the sonar once more and uses the compass to find the best open space route again.

The whole mecanism was mounted using an old 3.5" floppy cover, and the electronics are breadboarded to allow easy modifications and testing. It is powered from a 9V rechargable battery for the electronics, and the motors are using 4 AA batteries, also rechargable.

Email: erobles@erbots.com

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