Targeting

1, 2 and 3 Targets

Introduction

The purpose of this lab is to spin the servo to find an IR emitter, which is in the center of a target. Once the IR emitter has been located, the goal is to fire a laser at the center of the target. The robot could be in any position, such that the target could be anywhere in a 180 degree range in front of the robot.

First we were asked to make an algorithm based on the recorded data of the servo making a sweep.

Data

Here is an example of what the robot sees when it sweeps its servo

Note: We are using a moving average. As a result, we have to account for the error in degrees. The lowest point is not seen right away. Rather, it must make its way through the moving average first.

Since we are using a moving average of size 4, it is off by about two degrees. You will see corrections for this n our code.

An Algorithm

Our basic idea for code is:

Sweep the 180 degrees with the servo
At each degree, take a reading and check if it is the lowest value.
If the current degree is the lowest value, save that location
At the end of the sweep, simply go back to the degree that had the lowest value

Code

void target() {

  delay(200);                                              //wait for button to lift

  if (!myservo.attached()) myservo.attach(servoPin);

  myservo.write(0);                                        //move servo to beginning

  long now=millis();

  while(millis()-now<2000);                                //wait for it to get there

  //setup moving average for readings

  int iravg[4] = {0,0,0,0};

  int total=0;

  for (byte i=0; i<4;i++) total+=iravg[i]=analogRead(analogIRPin);

  byte iravgindex=0;

  int lowestDegree=0;                                      //for keeping track of the lowest point

  int readings[180];                                       //keeps every reading so we don't have to sweep again

  for (byte degree=0;degree<180;degree++) {                //for every degree

    myservo.write(degree);                                 //move the servo to that degree

    now=millis();

    while(millis()-now<20);                                //wait for it to get there

    //update the moving average

    total=total-iravg[iravgindex]+(iravg[iravgindex]=analogRead(analogIRPin));

    iravgindex=(iravgindex+1)%4;

    readings[degree]=analogIRSensor=total/4;               //and store that reading

    if (readings[degree]<readings[lowestDegree]) lowestDegree=degree; //if the new reading is lower, save it

    if (useSave) saveData(useSave);                        //logs data if enabled

  myservo.write((lowestDegree-4<0)?0:lowestDegree-4);      //go to lowest point. -4 accounts for moving average.

  now=millis();

  while(millis()-now<2000);                                //delay for servo to get there

  digitalWrite(laserPin, HIGH);                            //turn on laser

  now=millis();

  while(millis()-now<5000);                                //for five seconds

  digitalWrite(laserPin, LOW);                             //and turn it off again.

  //code for 2nd and 3rd targets. simply a repeat of what's above without the servo sweep.

  for (int i =0; i<2; i++) {

    while (digitalRead(button)==LOW) digitalWrite(ledPin, HIGH);  //the light comes on when it's ready for the next pass

    digitalWrite(ledPin,LOW);                                     //after button is pressed, turn off the light and cont.

    for (byte index=((lowestDegree-15<0)?0:lowestDegree-15); index<((lowestDegree+15>180)?180:lowestDegree+15); index++)

      readings[index]=1000; //fill in array +/- 15 degrees on either side of the previous lowest point.

    lowestDegree=0;

    for (byte degree=0;degree<180;degree++) {

      if (readings[degree]<readings[lowestDegree])  lowestDegree=degree; //find the new lowest point

      if (useSave) saveData(useSave);                      //log data

    myservo.write((lowestDegree-4<0)?0:lowestDegree-4);    //go to lowest point. -4 accounts for moving average.

    now=millis();

    while(millis()-now<2000);                              //delay for servo to get there

    digitalWrite(laserPin, HIGH);                          //turn on laser

    now=millis();

    while(millis()-now<5000);                              //for five seconds

    digitalWrite(laserPin, LOW);                           //and turn it off again.

  servoOff();

  currentMenu = draw;                                      //back to main menu

The Bonus Mark

Could we do it with three targets? Watch below to find out.

received_412295782485812.mp4

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