Rescue robot challenge

Learn

What you’ll build

A robot for a rescue-style challenge, inspired by events such as RoboCup Junior Rescue Line: follow a line through a “disaster zone”, detour around obstacles blocking the line, and find a “victim” (a coloured or silver object) at the end. Rules differ between events, so this project uses simplified rules you can set up at home.

Home challenge rules

1. Black line track with curves, on white.
2. One obstacle (a box) placed on the line: go around it and re-find the line.
3. A green or red end zone: stop there and signal (LED or buzzer).
4. Time limit: 3 minutes.

Parts

Line follower car plus a front distance sensor and a colour sensor (TCS34725) looking down, or use a third line sensor and a coloured tape end zone.

Behaviour plan (state machine)

State	Does	Leaves when
FOLLOW	Line following	Obstacle < 10 cm → DETOUR; end colour seen → FINISH
DETOUR	Turn right, arc left around the box	A line sensor finds the line → REALIGN
REALIGN	Turn until the line is between the sensors	Aligned → FOLLOW
FINISH	Stop, flash and beep	—

Why this is hard

Every piece works alone; the challenge is integration: the detour must reliably end back on the line, and sensors must not confuse the obstacle box or the end zone with the line.

Examples

Skeleton of the program

rescue-skeleton.ino

enum State { FOLLOW, DETOUR, REALIGN, FINISH };
State state = FOLLOW;
unsigned long since = 0;

void enter(State s) { state = s; since = millis(); }

void loop() {
  switch (state) {
    case FOLLOW:
      followLine();                                   // from the line follower project
      if (frontCm() < 10) enter(DETOUR);
      if (endZoneSeen()) enter(FINISH);
      break;
    case DETOUR:
      if (millis() - since < 400) drive(150, -150);   // turn right
      else drive(90, 170);                            // arc left round the box
      if (millis() - since > 800 && (leftOnLine() || rightOnLine())) enter(REALIGN);
      break;
    case REALIGN:
      drive(120, -120);
      if (!leftOnLine() && !rightOnLine()) enter(FOLLOW);  // line now between sensors
      break;
    case FINISH:
      drive(0, 0);
      flashAndBeep();
      break;
  }
}

Fill in followLine(), frontCm(), endZoneSeen() and the others from earlier projects. Tune the times on your own robot.

Practice

Practise each part in the simulator

Line following:

Part 1: follow the line

▶ Run↺ Reset

Your code (JavaScript)Load starter code

Robot commands

• motors(left, right): wheel power, −100 to 100
• lineLeft(), lineRight(): true over the black line
• distance(): cm to the nearest thing ahead (max 200)
• distanceLeft(), distanceRight(): cm to the sides
• linePosition(): where the line is, −1 (left) to 1 (right), or null
• millis(): milliseconds since Run
• print(value): show a message below
• setup() runs once; loop() runs 50 times a second

Obstacle detection and detours:

Part 2: detours

▶ Run↺ Reset

Your code (JavaScript)// Detour practice: when blocked, turn right then arc left let since = -1; function loop() { if (since < 0 && distance() < 20) since = millis(); if (since >= 0) { const t = millis() - since; if (t < 600) motors(50, -50); else if (t < 3000) motors(35, 60); else since = -1; } else motors(55, 55); }Load starter code

Robot commands

• motors(left, right): wheel power, −100 to 100
• lineLeft(), lineRight(): true over the black line
• distance(): cm to the nearest thing ahead (max 200)
• distanceLeft(), distanceRight(): cm to the sides
• linePosition(): where the line is, −1 (left) to 1 (right), or null
• millis(): milliseconds since Run
• print(value): show a message below
• setup() runs once; loop() runs 50 times a second

Build the trackEasy

Lay out a home rescue track with tape: one gentle curve, one sharp curve, an obstacle on the line and a coloured end zone.

Reliable detourMedium

Tune your detour so it gets back onto the line 5 times out of 5. Record each attempt in a table.

Full runHard

Complete the whole course in under 3 minutes three times in a row. Write down what you changed between attempts.

Quick check

1. What makes a rescue robot harder than its parts?

Integration: combining behaviours reliablyIt needs more LEDsIt must be biggerNothing

2. Why add a REALIGN state after the detour?

To get the line back between the sensors before followingTo chargeTo play a soundIt’s not needed

3. Rules for real rescue competitions…

Are the same everywhereDiffer by event: read the current rulesDon’t existBan sensors

Check my answers