How To Build A Robot - Lesson 3: Build A Line Tracking Robot

Assembly Instructions

It is not difficult to assemble the Arduino robot. Please follow the following instruction.

Step 1: 
Firstly, you need 3 nylon supports and their accompanying screws and nuts.

Step 2: Attaching the Nylon supports
Using nuts, attach the nylon supports on top of the Mini sensors. When attaching the supports, please pay attention to their direction: the nuts and probes should both be in one direction.

Step 3: Assembling the sensor board
Remove the upper plate from the robotic platform. Then, attach the sensor board to the front of the platform.

Step 4: Assembling the line tracking sensor 
First, connect the sensor with the wire designated for data transmission. Then, use your M3 screws to affix the sensors to the expansion board protruding from the front of the platform. 

Configuring your Arduino Robot’s path

Transmission: How it works

How do we make the robot stay on its track? We need to ensure that the robot is consistently located in the middle of the track. The robot uses its 3 transmission sensors to calibrate its position relative to the track -- once it veers to the side, the robot will self-adjust back towards the middle. 

When Our robot moves, three conditions will happen.

(a)When the robot first begins moving along the track, only the middle sensor (B) detects the black line – the left and right sensors have not come into play yet. The car will remain centered along the track and move forward.

(b)After continuing on its track, the robot might start to veer off center. Under these circumstances, the left and right sensors will try to detect the black line and self-guide the robot back towards the track. For instance, if the robot veers towards the right side of the track, the car will need to re-center itself by turning towards the left – the left sensor will kick in and automatically turn the robot until it re-centers.

  
(c)Conversely, if the robot veers towards the left side of the track, the right sensor will kick in and adjust the robot’s path until it re-centers. 

Code Synopsis 

There’s no need to discuss the basic code – let’s just take a look at the part involving transmission.

    int RightValue;    //Right line tractor sensor on Pin 8

    int MiddleValue;   //Middle line tractor sensor on Pin 9

    int LeftValue;     //Left line tractor sensor on Pin 10

    //reading 3 pins values of Line Tracking Sensor

    RightValue=digitalRead(8);  

    MiddleValue=digitalRead(9);

    LeftValue=digitalRead(10);

Use three variables – RightValue, MiddleValue, LeftValue – to record the 3 sensors’ read values. 

The digitalRead(pin) function is used to read the digital Input/Output port value. If this part is still unclear, please check out our Terminology Manual or the Arduino website.

When the middle transmission sensor detects a black line (the track), it’ll produce a LOW energy output. When they detect a white space, they’ll produce a HIGH energy output.

Example A below illustrates the transmission code’s working principles. When the middle sensor detects a black line (the track), it’ll produce a LOW energy output. When the left/right sensors detect white space, they’ll produce a HIGH output.

    if (MiddleValue==LOW) {   //line in the middle

        Robot.Speed (100,100);  

        delay(10);

    }

    else if ((LeftValue==HIGH) && (RightValue==HIGH)) {     

        Robot.Speed (100,100);  

        delay(10);

    }

If the sensors detect the black line/track to the left while also detecting white space to the right, the robot will turn left. See Example B below:

    else if ((LeftValue==LOW)&&(RightValue==HIGH)){ 

        Robot.Speed (-100,100);  //turn left

        delay(10);

    }

Conversely, if the sensors detect the black line/track to the right while also detecting white space to the left, the robot will turn right. See Example C below:

    else if ((LeftValue==HIGH)&&(RightValue==LOW)){

        Robot.Speed (100,-100);  //turn right

        delay(10);

    }