← IGCSE Computer Science Paper 1

Example robot: domestic robots

A robot used in the home, such as a robot vacuum cleaner or lawnmower, that senses its surroundings and moves automatically to do a household job.

Part of: IGCSE Computer Science 0478 — 6.2 Robotics — Module 13

Understanding Example robot: domestic robots in IGCSE Computer Science Paper 1

What it does: A robot lawnmower cuts the grass by itself in a garden, so it is a domestic robot used at home. The wheels are part of the robot's frame, and the motors (actuators) turn them so the robot can move around. Drop (cliff) sensors detect a sudden change in floor height. The robot stops or turns, so it avoids falling. Storing dust is the job of the bin. A domestic robot is programmed and uses sensors, so it moves automatically. It does not need constant human control. Drop sensors send data to the microprocessor, which tells the wheels to stop or turn away from the edge.

Common mistakes: The IF statement is missing THEN. It should be IF wall_sensor = TRUE THEN so the robot vacuum turns when its sensor detects a wall. The loop condition is wrong. With FALSE the loop never runs, so the robot lawnmower would not cut any grass. It should be WHILE mower_on = TRUE.

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Learning
Duo
Which of these is a domestic robot?
A robot arm that welds car parts in a factoryA robot vacuum cleaner that cleans the living room floor
Matches
A robot vacuum cleaner has no sensors and just follows a fixed path
↓
A domestic robot needs sensors to sense its surroundings, such as walls and furniture, so it can avoid bumping into things
Applying
Meanings
Term
domestic robot
Meaning
A robot used in the home, such as a robot vacuum cleaner or lawnmower, that senses its surroundings and moves automatically to do a household job.
Practice
WHILE battery > 10
Testing
Gaps
battery > 20
Check Answer
Spots
1WHILE battery > 10
2 IF wall_sensor = TRUE

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Quick Questions

1. Which of these is a domestic robot?
A. A robot arm that welds car parts in a factory
B. A robot vacuum cleaner that cleans the living room floor ✓
A domestic robot is used in the home to do a household job. A welding arm is industrial, not domestic.
2. Which job could a robot lawnmower do?
A. Cut the grass in a garden by itself ✓
B. Pick fruit from trees on a large farm
A robot lawnmower is a domestic robot that does a household job: cutting the lawn at home. Fruit picking on farms is an agricultural role.
3. Which sensor job helps a robot vacuum cleaner avoid damage?
A. A sensor detects a wall so the robot turns away ✓
B. A wheel detects a wall so the robot turns away
Sensors detect the surroundings. Wheels are part of the mechanical structure and help the robot move.
4. Why does a robot vacuum cleaner have a drop sensor?
A. To detect stairs so it does not fall down them ✓
B. To store dust until the bin is emptied
Drop (cliff) sensors detect a sudden change in floor height. The robot stops or turns, so it avoids falling. Storing dust is the job of the bin.
5. In a robot vacuum cleaner, what are the wheels part of?
A. The sensors that detect walls and drops
B. The mechanical structure that lets it move around ✓
Wheels are part of the mechanical structure of the robot. Sensors are the input devices.

Match the Pairs

robot vacuum cleaner → A domestic robot that moves around a room on wheels and cleans the floor automatically
cliff sensor → A sensor that detects a drop, such as stairs, so the robot does not fall down
A domestic robot is used in the home to do a household job such as mowing the lawn → robot lawnmower
Wheels are the mechanical structure that lets a domestic robot move across the floor → wheels driven by motors
A robot vacuum cleaner has no sensors and just follows a fixed path → A domestic robot needs sensors to sense its surroundings, such as walls and furniture, so it can avoid bumping into things
A robot lawnmower is not a robot because it is used in a garden at home → Being used in the home or garden does not stop it being a robot; it is a domestic robot because it senses and moves automatically

Key Term

domestic robot
A robot used in the home, such as a robot vacuum cleaner or lawnmower, that senses its surroundings and moves automatically to do a household job.

Fill in the Blanks

1. WHILE battery > 20 IF wallSensor = TRUE THEN turn(90) ENDWHILE
Hint: Type the keyword that makes the robot vacuum keep repeating its cleaning while the battery is above a level.
2. IF dropSensor = TRUE THEN stopWheels() ENDIF
Hint: Type the keyword that closes the selection block after the robot reacts to a drop.
3. wheelSpeed ← 5 IF dropSensor = TRUE THEN wheelSpeed ← 0 ENDIF
Hint: Type the number that means the wheels are not turning when a drop is sensed.
4. REPEAT mowGrass() UNTIL batteryLow = TRUE
Hint: Type the keyword that ends a post-condition loop for the robot lawnmower once the condition is true.
5. distance ← frontSensor() IF distance < 5 THEN turn(90) ENDIF
Hint: Type the comparison operator that checks whether the wall is closer than 5 cm.

Spot the Error

Question 1
A WHILE battery > 10
B IF wall_sensor = TRUE
C turn_right()
D ENDIF
E ENDWHILE
Line B — The IF statement is missing THEN. It should be IF wall_sensor = TRUE THEN so the robot vacuum turns when its sensor detects a wall.
Question 2
A mower_on ← TRUE
B WHILE mower_on = FALSE
C cut_grass()
D ENDWHILE
Line B — The loop condition is wrong. With FALSE the loop never runs, so the robot lawnmower would not cut any grass. It should be WHILE mower_on = TRUE.
Question 3
A IF path_clear = TRUE THEN
B left_wheel ← ON
C right_wheel ← OFF
D ENDIF
Line C — To drive straight forward, both wheels must turn. With the right wheel OFF the robot would spin around. It should be right_wheel ← ON.
Question 4
A battery ← 100
B WHILE battery > 20
C clean_floor()
D battery ← battery + 1
E ENDWHILE
Line D — The battery level should go down as the robot cleans. Adding 1 means the battery never drops below 20 and the loop never ends. It should be battery ← battery - 1.
Question 5
A WHILE floor_dirty TRUE
B vacuum_on()
C move_forward()
D ENDWHILE
Line A — The condition is missing the comparison operator. It should be WHILE floor_dirty = TRUE.

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