Objective:

The goal of this milestone is to implement line following and turning functionalities to our robot.

Line Following:

• The first step was to have our robot follow a line of black tape
• We used 2 IR sensors to detect the black line by determining a threshold value
• If a sensor went out of line, the corresponding servo would compensate by speeding up that side of the wheel so that the robot would remain on the line
  • If left sensor went out of line, speed up left servos
  • If right sensor went out of line, speed up right servos
  • Otherwise, servos rotate at same rate

               if(lRead<thresh){  // left side is out of line
                    left.write(170);
                    right.write(86);
                  }
                  else if(rRead<thresh){   // right side is out of line
                    left.write(94);
                    right.write(10);
                  }
                  else{     // go straight
                    left.write(100);
                    right.write(80);
              

• We tested the robot on a curved line as well

Figure-8:

Detecting Intersections:

• Our next step was to add two additional sensors to detect an intersection
• We added two wide sensors near the wheels, one on each side of the robot
• When either wide sensor detected black, we detect an intersection

Figure-8 Implementation:

• We then implemented turning

              void leftTurn(){
                while(analogRead(0)>=thresh || analogRead(1)>=thresh){
                    right.write(77);
                    left.write(77);
                }while(analogRead(0)<=thresh){
                    right.write(77);
                    left.write(77);
                }
                right.write(90);
                left.write(90);
              }
  
              void rightTurn(){
                while(analogRead(0)>=thresh || analogRead(1)>=thresh){
                    right.write(103);
                    left.write(103);
                }while(analogRead(1)<=thresh){
                    right.write(103);
                    left.write(103);
                }
                right.write(90);
                left.write(90);
              }
              

• When the robot detected an intersection, we programmed it to turn until the line/inner sensors detected black again (turn is finished)
• To implement the figure 8, we programmed the robot to turn left whenever it detects an intersection 3 times, go straight at the next intersection, and turn right when it detects an intersection 3 times. This sequence is in a loop, so the robot continues to navigate a figure 8
• To go straight we added a helper function goStraight():

              void goStraight(){
                while(analogRead(2)>=thresh || analogRead(3)>=thresh){
                  left.write(100);
                  right.write(80);  
                }
              }
              

• The code below shows the first few cases that we loop through while traversing the figure 8. Notice we used a cooldown to ensure that the robot doesn't detect the same intersection more than once.

              int detectCooldown = 0;
              int DETECT_COOLDOWN = 50;
              .
              .
              .
               if((lwRead >= thresh || rwRead >= thresh) && detectCooldown == 0){
                  switch (intsec){
                    case 0:
                      Serial.println("Case0");
                      intsec++;
                      detectCooldown = DETECT_COOLDOWN;
                      roboStop = 0;
                      goStraight();
                    break;
                    case 1:
                      Serial.println("Case1");
                      intsec++;
                      detectCooldown = DETECT_COOLDOWN;
                      roboStop = 0;
                      leftTurn();
                    break;
                    case 2:
                      Serial.println("Case2");
                      intsec++;
                      detectCooldown = DETECT_COOLDOWN;
                      roboStop = 0;
                      leftTurn();
                    break;
              

Final Robot of Milestone 1: