Follow black line

[antogrim2]

I trying to write a program in which my robot would follw a black line, but i don't know how to do this...Can you help me? This is an university project, most important for me...thanks a lot...

[ChrisB01]

What kit do you have, most inportant light sensors and nxt/rcx's. There are diffrent ways of atacking the problem but it depends on what kit you have.

Thanks,

Chris

[antogrim2]

[quote="ChrisB01"]What kit do you have, most inportant light sensors and nxt/rcx's. There are diffrent ways of atacking the problem but it depends on what kit you have.

Thanks,

Chris[/quote]

I have RCX. and one LightSensor.

[JavaMan]

I hope you have two motors, or one with a differential gear.

Here is the basic steps of a line-following robot I built with a rcx:

Robot drives forward a little bit.
Checks to see of light sensor is still reading black:
If it is then drive forward a little bit more.
If it is not then turn left a little bit then turn right a little bit to try to find the black line.
When the line is found the drive forward a little bit more.
Repeat process.

Make sure you have the RCX drive forward only a little bit because if it drives forward too much then you loose the black line, and finding it can be hard.

Jman

[antogrim2]

[quote="JavaMan"]I hope you have two motors, or one with a differential gear.

Here is the basic steps of a line-following robot I built with a rcx:

Robot drives forward a little bit.
Checks to see of light sensor is still reading black:
If it is then drive forward a little bit more.
If it is not then turn left a little bit then turn right a little bit to try to find the black line.
When the line is found the drive forward a little bit more.
Repeat process.

Make sure you have the RCX drive forward only a little bit because if it drives forward too much then you loose the black line, and finding it can be hard.

Jman[/quote]

Thanks very well...do you know something about color recognizing of light sensor? I have understood that the sensor recognizes accuratly only 3 colors: Black White and Grey...in raw mode

[JavaMan]

Yes, the light sensor for the RCX can only detect light intensity levels. So, usually black has a lower intensity and white has a higher intensity. Gray would have a intensity somewhere in the middle. It can't detect different wavelengths. Here is a site I found describing how to build a Color Sensor
http://www.extremenxt.com/MUX2.HTM for the RCX.

Hope that helps.
Jman

[antogrim2]

[quote="JavaMan"]I hope you have two motors, or one with a differential gear.

Here is the basic steps of a line-following robot I built with a rcx:

Robot drives forward a little bit.
Checks to see of light sensor is still reading black:
If it is then drive forward a little bit more.
If it is not then turn left a little bit then turn right a little bit to try to find the black line.
When the line is found the drive forward a little bit more.
Repeat process.

Make sure you have the RCX drive forward only a little bit because if it drives forward too much then you loose the black line, and finding it can be hard.

Jman[/quote]

Hi,
I have written an algorithm in which robot go on the left OR on the right, but it isn't up to decide run-time the direction. Can you help me, please? I post you my alg.

Robot.backward(3,3);
Robot.pause(150);
Robot.right(3,3); // or Robot.left(3,3);
Robot.pause(80);
Robot.forward(1,1);

it is called when state of light sensor changed from black to white. The parenthetical numbers of the methods forward right and backward indicate the power of motors.

[JavaMan]

Ok, I think I understand what you mean.
I suggest when the rover notices that the the light goes from black to white:

Robot.backward(3,3);
Robot.pause(150);
Robot.right(3,3);
Robot.pause(80);
Robot.forward(1,1);
if(light.equals(white)){
Robot.left(3,3);
Robot.pause(80);
Robot.backward(3,3);
Robot.pause(150);
Robot.left(3,3);
Robot.pause(80);
Robot.forward(1,1);
//Hopefully the line is found.
}
else{
regular movement...
}


You could also have the robot sweep some degress left and right until he finds the line. Of course, depending on how curly your line is may screw this up.

Jman

[antogrim2]

[quote="JavaMan"]Ok, I think I understand what you mean.
I suggest when the rover notices that the the light goes from black to white:

Robot.backward(3,3);
Robot.pause(150);
Robot.right(3,3);
Robot.pause(80);
Robot.forward(1,1);
if(light.equals(white)){
Robot.left(3,3);
Robot.pause(80);
Robot.backward(3,3);
Robot.pause(150);
Robot.left(3,3);
Robot.pause(80);
Robot.forward(1,1);
//Hopefully the line is found.
}
else{
regular movement...
}


You could also have the robot sweep some degress left and right until he finds the line. Of course, depending on how curly your line is may screw this up.

Jman[/quote]


Ok thanks...I try this solution and then tell you results. bye

[DaliMe]

Thank you very much! I also hae the similar task in my course work. Read lots of manuals but I couldn't understand the logic. Now it is clear.

[rachael17]

So do I!!! Thank you very much cialis for explanation, very helpful for me!

[maccast]

I took some of the info in this thread and combined it with some other code and tutorials to write my version of a very simple line follower program. I am VERY new to lejos, so I'm open for any suggestions for improvement. I am posting the code mainly to help anyone else who might be working to figure this out as I could't find many actual code examples. This is code for the RCX and mine is a RCX 1.0. I am having one issue where at a certain point the RCX crashes (basically locks up on whatever the current command being executed is), but I'm not sure if that is me reaching a hardware limit or if there is an actual issue with this code. The RCX will make a beep and the LCD will display a 62 with a carrot (^) pointing to the #2 sensor. The number to the right of the "run" character will also change from a 0 to a 5. Not sure if that is significant or not. Again any suggestions are appreciated.

Code: Select all

import josx.platform.rcx.*;
import josx.robotics.*;

//////////////////////////////////////
/**
* Line follower
*
* @author Adam Christianson
* @url   http://www.terraform.com
* @version 1.0
*/
public class LineFollow {       

    ////////////////////////////////////////////
    // public methods
    ////////////////////////////////////////////

    ////////////////////////////////////////////
    /**
     * main method
     * @throws InterruptedException
     */
    public static void main(String[] args)
        throws InterruptedException {
      Sensor.S1.setTypeAndMode (3, 0x80);
      Sensor.S1.activate();
      Sensor.S1.addSensorListener (new SensorListener() {
        public void stateChanged (Sensor src, int oldValue, int newValue) {
          // Will be called whenever sensor value changes
          LCD.showNumber(newValue);
         TimingNavigator robot = new TimingNavigator(Motor.C, Motor.A, 1.6f, 0.54f);
         if (newValue > 35 ) {
            robot.travel(-15);
            pause(300);
            robot.rotate(-45);
            pause(300);
         } else {
            robot.forward();
         }
          try {
            Thread.sleep(100);
          } catch (InterruptedException e) {
            // ignore
          }
        }
      });      
      // just run until RUN button is pressed again
       Button.RUN.waitForPressAndRelease();
   } //main()
   
   public static void pause(int delay)
    {
      try { Thread.sleep(delay); }
      catch (InterruptedException ie) { }
    }
}


[Charis]

Yes, the light sensor for the RCX can only detect light intensity levels. So, usually black has a lower intensity and white has a higher intensity. Gray would have a intensity somewhere in the middle. It can't detect different wavelengths. Here is a site I found describing how to build a Color Sensor
http://www.extremenxt.com/MUX2.HTM for the RCX.

Hope that helps.
Jman

Thank you very much for this link! I have been wanting to create a sensor like this for a project that I am working on. It is a robot that will analyze and document the skid marks on a road after an accident, to help aid in accident reconstruction. I know that this might sound like a somewhat impractical, or far fetched concept, but if I get it working the way I designed, I can actually see it being quite a helpful contraption. I already have a coupe potential buyers waiting for a prototype. I am really excited about this project, and hope all goes well.