Roamer by Harm Andries Kingma

Roamer is an obstacle avoider. Its sole purpose in life is to drive around without colliding into
any obstacles on its path.To detect obstacles, Roamer makes use of a Polaroid sonar module with the
sensor element mounted on a servo. The sensor is the black turred mount on the front of the robot.
The servo is used to sweep the sensor from left to right in order to give the robot a wide field of
view. When it detects an obstacle it will turn left or right, depending on the direction the sensor
turret is facing. If it sees an obstacle on the left it will turn right and if an obstacle is
detected on the right it will turn left. Nothing more complicated than that. 

Roamer makes use of differential steering to navigate its way through the world. Its drivetrain
consists of three wheels. The two big front wheels drive the robot and are mounted on hobby servo's
modified for continuous rotation. The small wheel at the rear is a castor wheel and serves to keep
the robot upright. Steering goes as follows: When Roamer wants to go forward, both front wheels turn
forward. When he wants to turn left, the wheel on the right turns forward and the wheel on the left
backward. Similarly, when a right turn is necessary, the wheel on the left turns forward and the
wheel on the right backward. 

The brain of Roamer is an ATMEL AVR AT90S8515 microcontroller programmed completely in assembly.
This chip controls the complete bot: Sensors, display, locomotion, behaviour etc.

On my website: you can also find a movie of roamer in action. My
other three robots are are described there. 


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