Create your Line follower Robot

Create your Line follower Robot

Line follower (or Grid follower) is a Autonomous robot, which follows a color line works on microcontroller.

Mechanical Features of a Line Follower RobotJ

Has a zero degree turning radius (can rotate in place). It has near omni-directional movement, minus singularities at maximum servo rotations and the time it takes to turn a wheel. This allows Taurus 2(Line follower=T2) to travel sideways, forwards, straff, and even drive in sinusoidal shapes - yet still face in the same direction. And lastly, it can handle rough terrain.

Mechanical DesignJ

T2 was made in 2D CAD (my first time using CAD) and built using HDPE and aluminum as the chassis material. A long metal rod attached to two ball bearings created the rocker-bogey system, as shown in this assembly picture:

Electrical Design J

I used a PIC based microcontroller programmed in C. Eight digital outputs controlled each of the servos independently, while the Microcontroller camwas interfaced by the serial port. The eight servos drained large amounts of power, so I had to use two NiCad battery packs. As additional contactless 'bumper' sensors I made three infrared emitter detectorsensors, as shown here:

Programming and ControlJL

I programmed T2 to read in the middle mass (centroid of a color in an image) of the colors green and blue in whatever it saw from the camera. I then would have the servos rotate in such a way so that T2 would always drive to that middle mass. I wanted T2 to follow a white line, and so this worked really well. To control four wheels independently, you must have each wheel turn to a specific angle so that the axis of each wheel goes to a single central point (or axis of rotation). This image will explain it well:

If the front two wheels had equal angles, the rotation axis will not be common, and you will have high friction and skidding. If the wheels were to never change the angles as shown in the above image, the robot would follow the imaginary circle perfectly about the common central axis. Just use basic trigonometry, knowing the turn radius and wheel locations, to determine required wheel angles.

When I programmed it, I made a continuous fuzzy logic algorithm to relate wheel angles to target direction. The front wheels and back wheels were inverted so I just needed to do two angle calculations per cycle. I also did a few mixes of other algorithms, as seen in the above video. Another method is to make a trigonometric lookup table to control wheel angles.

Parts Used

 (2) 7.2V nicad battery packs .

(1) CMUcam .

(1) Cerebellum Microcontroller, by AVR.

(3) IR Sensors.

(8) HS-311 servos .

(1) null modem cable(jumper wires) .

(4) foam 4 inch diameter model aircraft wheels .

(2) ball bearings (found in a scrap pile).

Chess.

Help:- http://www.societyofrobots.com/