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Cambridge IGCSE0478

Automated systems

Computer Science 0478 Chapter Notes

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Automated systemsRoboticsArtificial intelligence
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In this chapter

  1. 1Sensor, microprocessor and actuator
  2. 2How the three parts work together
  3. 3Naming the right sensor
  4. 4Applying the system to a scenario
  5. 5Advantages and disadvantages
  6. 6What robotics is
  7. 7Characteristics of a robot
  8. 8Sensors, microprocessors and actuators
  9. 9How the parts work together
  10. 10Roles, advantages and disadvantages
  11. 11What artificial intelligence is
  12. 12The characteristics of AI
  13. 13The parts of an expert system
  14. 14How an expert system finds a solution
  15. 15Machine learning

1. Sensor, microprocessor and actuator

An automated system uses three parts in turn. A sensor is an input device. It measures its surroundings, such as the temperature or the light level, and sends the data to the microprocessor.

The microprocessor processes the data. An actuator is an output device. It converts a digital signal into physical movement.

Examiner insight

“Candidates must understand that it is not the sensor that detects the change, that the sensor just measures the environment.” “An actuator converts a digital signal into physical movement for example to move a motor to open a door, it does not display a message on a digital screen.”

Worked example 12 marks

An automatic door opens when a person stands within 1 metre of it. State the name of the part that makes the door move, and what it does.

  1. 1

    An actuator (for example a motor) [1]

  2. 2

    It converts a digital signal from the microprocessor into physical movement [1]

2. How the three parts work together

The sensor continuously sends data to the microprocessor. The data is converted to digital form.

The microprocessor compares the data with a stored value. If the result is true, it sends a signal to the actuator.

The pseudocode shows this decision for a window blind that closes when the light level is above 800 lux.

``` WHILE TRUE DO INPUT LightLevel IF LightLevel > 800 THEN SendSignal ← TRUE ELSE SendSignal ← FALSE ENDIF ENDWHILE ```

Examiner insight

“There seem to be a misconception from some candidates that the sensor only takes a sample when it notices something has changed or moved.” “Candidates needed to demonstrate their understanding of the steps involved in this decision and action, i.e. the value is compared, and then if the result is true the microprocessor sends a signal to the actuator to make the movement.”

Worked example 13 marks

A window blind closes when the light level is above 800 lux. Describe how the microprocessor makes the blind close.

  1. 1

    It compares the data from the light sensor with the stored value of 800 lux [1]

  2. 2

    If the light level is greater than 800 lux, the result is true [1]

  3. 3

    It sends a signal to the actuator, which moves the blind to close it [1]

3. Naming the right sensor

Name the type of sensor, not an example of it. A gas sensor measures gases such as oxygen and carbon dioxide. A pH sensor measures acidity; a moisture sensor does not.

A sensor that detects a person nearby is an infra-red sensor. Other types in the papers are light, pressure and level sensors.

Examiner insight

“Some candidates gave motion sensor which was not precise enough to indicate the actual sensor that would be used to detect the motion, which is most commonly an infra-red sensor.” “The most common error made was candidates not using the correct name for a type of sensor and rather listing and example of the type of sensor, such as O2 sensor or CO2 sensor for gas sensor, and acidity sensor for pH sensor.”

Worked example 13 marks

Name the most suitable sensor for each application.

(a) Switching a street lamp on at dusk.

(b) Checking the acidity of soil in a greenhouse.

(c) Detecting a person within 1 metre of a door.

  1. 1

    (a) light sensor [1]

  2. 2

    (b) pH sensor [1]

  3. 3

    (c) infra-red sensor [1]

4. Applying the system to a scenario

A question names a scenario. Use its details: its sensor, its values and what its actuator moves.

Name the sensor, say it sends data continuously, and say the microprocessor compares the data with the stored value given in the question. Then say what the actuator does.

Examiner insight

“Many candidates provided a generic description of a system that uses a sensor and a microprocessor, and did not relate their description to the system given in the question.” “Some candidates applied it to a different context such as an automatic lighting system or a security system.”

Worked example 15 marks

A greenhouse window opens automatically when the temperature is above 30 °C. Describe how the sensor, microprocessor and actuator work together.

  1. 1

    A temperature sensor measures the temperature in the greenhouse [1]

  2. 2

    It continuously sends the data to the microprocessor, converted to digital form [1]

  3. 3

    The microprocessor compares each reading with the stored value of 30 °C [1]

  4. 4

    If the reading is above 30 °C, it sends a signal to the actuator [1]

  5. 5

    The actuator (a motor) converts the signal into physical movement and opens the window [1]

5. Advantages and disadvantages

An advantage or disadvantage must fit the scenario and the person the question asks about. A generic point such as "it can work 24/7" is not an advantage to an employee.

Give a benefit, not a feature. "It can measure the heat level" is a feature. A benefit is that the system can instantly indicate when the level is too hot.

Disadvantages that earned marks were high setup or maintenance costs, and that robots could take employees' jobs. Scenarios in the syllabus are industry, transport, agriculture, weather, gaming, lighting and science.

Examiner insight

“Many candidates gave generic reasons such as the robots will not need to take breaks. They did not consider the context given in the question and were not relevant as advantages to the employee.” “It would be beneficial for candidates to state a benefit, rather than a feature, of the sensor in this context.”

Worked example 14 marks

A factory uses an automated system with a temperature sensor to control an oven on its production line. Give two advantages of the system to the factory owner and two disadvantages of using it.

  1. 1

    Advantage: the system can work 24/7, so the owner's oven keeps running without breaks [1]

  2. 2

    Advantage: it measures the oven temperature and can instantly indicate when the oven is too hot [1]

  3. 3

    Disadvantage: high setup or maintenance costs for the owner [1]

  4. 4

    Disadvantage: the system could take employees' jobs on the production line [1]

Recap

  • A sensor measures its surroundings and sends the data to the microprocessor.
  • A microprocessor compares the data with a stored value.
  • An actuator converts a digital signal into physical movement.
  • The sensor sends data continuously, not only when something changes.
  • Name the type of sensor, for example infra-red, light, pH or gas.
  • Use the details of the scenario in every answer.
  • Fit each advantage or disadvantage to the scenario and to the person asked about.

6. What robotics is

Robotics is a branch of computer science. It incorporates the design, construction and operation of robots.

Robotics is the field of study. A robot is one thing the field produces. Examples include factory equipment, domestic robots and drones.

Examiner insight

“The stronger responses included a description of the design and construction of robots, whilst the weaker responses described a robot as simulating human actions.”

Worked example 12 marks

State what is meant by robotics.

  1. 1

    a branch of computer science [1]

  2. 2

    that incorporates the design, construction and operation of robots [1]

7. Characteristics of a robot

The syllabus lists three characteristics of a robot. It has a mechanical structure or framework. It has electrical components, such as sensors, microprocessors and actuators. It is programmable. Mark schemes also credit that it can move.

Artificial intelligence is not on this list. Not all robots have artificial intelligence.

Examiner insight

“Some candidates described the actions of the drone and how it worked, instead of its characteristics related to it being a robot.” “Some candidates gave an inaccurate response of ‘artificial intelligence’. It would be beneficial for candidates to understand that not all robots have artificial intelligence.”

Worked example 12 marks

A drone is used to search for lost animals. The drone is a flying device that can be autonomous or operated using a remote control. The drone is a robot. Give two characteristics of the drone that identify it as a robot.

  1. 1

    any two from: mechanical structure / framework, electrical components, programmable, it can move [2]

8. Sensors, microprocessors and actuators

A sensor sends data to the microprocessor. To identify if an object is nearby, mark schemes credit a proximity sensor, an infra-red sensor, a light sensor or a magnetic field sensor. An acoustic sensor identifies a sound, such as a clap.

A microprocessor is an integrated circuit on a single chip that performs all the functions of a CPU.

An actuator produces physical movement. It is used to stop, change or control the robot.

Examiner insight

“Some candidates gave motion or movement sensor. These terms require more precision as to that actual type of sensor within it, for example infra-red.” “Some candidates linked a microprocessor to an embedded system and defined an embedded system instead of a microprocessor.”

Worked example 12 marks

The drone has a built-in system to stop it from crashing into objects, for example a tree. The system uses sensors and a microprocessor.

(i) Identify one sensor that could be built into the drone to detect if it is near an object.

(ii) State what is meant by a microprocessor.

  1. 1

    (i) proximity sensor // infra-red sensor [1]

  2. 2

    (ii) any one from: an integrated circuit that performs all the functions of a CPU, an integrated circuit on a single chip [1]

9. How the parts work together

The sensor continually sends digitised data to the microprocessor. The microprocessor compares the data to a stored value. If the test is true, it sends a signal to the actuator. The actuator makes the movement. If the test is false, no action is taken.

The process repeats until the robot is turned off.

Examiner insight

“Few candidates were able to demonstrate an understanding of a sensor continually sending data to the microprocessor for analysis, instead suggesting that the sensor only sends data when an object is detected.” “Candidates needed to demonstrate their understanding of the steps involved in this decision and action, i.e. the value is compared, and then if the result is true the microprocessor sends a signal to the actuator to make the movement.”

Worked example 13 marks

A child has a robot animal. If the robot animal is walking and it senses an object is less than 10 cm away, it will stop. The sensor continuously sends digitised data to the microprocessor. Describe how the microprocessor uses the data from the sensor to stop the robot animal when an object is less than 10 cm away.

  1. 1

    the microprocessor compares the received data to the stored value (of 10) [1]

  2. 2

    if the value received is less than 10, it sends a signal to stop the robot [1]

  3. 3

    the signal is sent to an actuator that is used to stop the robot [1]

10. Roles, advantages and disadvantages

Robots can be used in industry, transport, agriculture, medicine, domestic settings and entertainment. A drone that searches for lost animals is an example.

An advantage must be an advantage to the person the question names. Robots do not need to take breaks, but that helps the employer. It does not help the employees.

Disadvantages include that a robot is expensive to purchase and that robots could take employees' jobs.

Examiner insight

“Many candidates gave advantages to the employers instead of the workers.” “The most common correct disadvantage given is that the robots could take employees jobs.”

Worked example 12 marks

A factory replaces some of its workers with robots. Give two disadvantages of using robots in the factory.

  1. 1

    a robot is expensive to purchase [1]

  2. 2

    the robots could take employees' jobs [1]

Recap

  • Robotics is a branch of computer science: the design, construction and operation of robots.
  • A robot has a mechanical structure, electrical components and is programmable.
  • Artificial intelligence is not a key characteristic of a robot: not all robots have it.
  • A microprocessor is an integrated circuit on a single chip that performs all the functions of a CPU.
  • The sensor continually sends data. The microprocessor compares it to a stored value. If true, it signals the actuator.
  • An advantage must help the person the question names: no breaks helps the employer, not the workers.

11. What artificial intelligence is

Artificial intelligence (AI) is a branch of computer science. It deals with the simulation of intelligent behaviours by computers.

AI is not the same as a robot. Not all robots have AI, and AI does not define a robot.

Examiner insight

“It would be beneficial for candidates to understand that not all robots have artificial intelligence.”

Worked example 12 marks

State what is meant by artificial intelligence (AI).

  1. 1

    AI is a branch of computer science. [1]

  2. 2

    It deals with the simulation of intelligent behaviours by computers. [1]

12. The characteristics of AI

The main characteristics of AI are the collection of data and the rules for using that data, and the ability to reason.

AI can also include the ability to learn and adapt.

A characteristic is a feature of AI itself. A scenario that uses AI, or a type of AI such as an expert system, is not a characteristic.

Examiner insight

“This question asked for the characteristics of artificial intelligence; some candidates describe different scenarios that could make use of artificial intelligence or described different types or categories of artificial intelligence, which did not answer this question.” “Some candidates repeated the characteristics given in the question, or gave this in another form, for example that it learns from its mistakes.”

Worked example 11 mark

A computer game uses artificial intelligence (AI) to create extra characters (players) in the game. One characteristic of the AI is that it can adapt and learn. Give one other characteristic of the AI.

  1. 1

    It collects data, or it applies rules to the data, or it has the ability to reason. [1]

13. The parts of an expert system

An expert system is one of two kinds of AI system you must know. The other is machine learning.

An expert system has four parts: a knowledge base, a rule base, an inference engine and an interface.

Examiner insight

“Candidates seemed to either know this fully, or not at all.” “They mainly identified the component parts of an expert system and what they contain.”

Worked example 14 marks

A doctor uses an expert system to help find the cause of an illness. Name the four components of the expert system.

  1. 1

    Knowledge base [1]

  2. 2

    Rule base [1]

  3. 3

    Inference engine [1]

  4. 4

    Interface [1]

14. How an expert system finds a solution

The user inputs data about the problem. The inference engine uses this data.

It searches for similar knowledge in the knowledge base and applies it to the rule base to find a solution. If it needs more data, it decides which question to ask next.

When a question asks how an expert system works, describe the role of each part in the context given. Naming the parts is not enough.

Examiner insight

“Very few candidates were able to accurately describe the role of the inference engine.” “Some candidates were able to name some or all of the components involved but very few could describe their role in the process.”

Worked example 13 marks

The computer game has an expert system that can be used to find a solution to any problems with the game. The expert system uses an inference engine. Explain the role of the inference engine in finding a solution to a problem with the game.

  1. 1

    It uses the data input by the user about the problem. [1]

  2. 2

    It searches for similar knowledge in the knowledge base. [1]

  3. 3

    It applies it to the rule base to find the solution. [1]

15. Machine learning

Machine learning is when a program has the ability to automatically adapt its own processes and/or data.

One way a program can do this is to store successful and unsuccessful actions, then use them the next time.

When a question asks how machine learning is used, apply it to the context. Do not only define it.

Examiner insight

“Few candidates were able to explain how machine learning would be used in the given context. Most candidates just gave a description of what is meant by machine learning.” “Some of the weaker responses described the use of an expert system in this scenario, which is not appropriate for the scenario due to there not being a user to answer the questions to move to an outcome.”

Worked example 14 marks

A child has a robot animal. The robot animal uses artificial intelligence (AI). Explain how the robot animal can use AI to learn where objects are in a room.

  1. 1

    It can use machine learning, adapting its own data/rules/processes. [1]

  2. 2

    It can create a (digital) map of the room, recording the shape and dimensions of the room. [1]

  3. 3

    It can record/store the location of objects. [1]

  4. 4

    It can update its map to record when objects are moved, removed or added. [1]

Recap

  • AI is a branch of computer science that simulates intelligent behaviours by computers.
  • AI characteristics: the collection of data and the rules for using it, the ability to reason, and it can include the ability to learn and adapt.
  • An expert system has a knowledge base, a rule base, an inference engine and an interface.
  • The inference engine uses the user's data, searches the knowledge base and applies it to the rule base.
  • Machine learning is a program that automatically adapts its own processes and/or data.
  • Apply machine learning to the context in the question. Do not only define it.

End-of-chapter exercise

Test yourself on the whole chapter. Work through these before moving on.

  1. State what a sensor does and what an actuator does in an automated system.2 marks
  2. A greenhouse system checks the acidity of the soil. Name the sensor it needs.1 mark
  3. A door opens when a person is within 1 metre of it. Name the sensor the system needs.1 mark
  4. A barn has a roof vent that closes when the temperature is below 12 °C. A temperature sensor sends data to a microprocessor. State what the microprocessor does with the data.2 marks
  5. A fish tank heater switches on when the temperature sensor reads below 22 °C. Four readings in order are 24 °C, 23 °C, 22 °C and 21 °C. Give the first reading at which the heater switches on, and why.2 marks
  6. A student says: "The sensor only sends data to the microprocessor when the light level changes." Explain why this is wrong.2 marks
  7. A weather station uses an automated system with a temperature sensor to warn of frost. A student writes this advantage: "It can measure the temperature." Explain why this earns no mark, and give a better answer.2 marks
  8. A factory fits an automated system to pack boxes. A question asks for an advantage and a disadvantage to the employees. A student writes: "Advantage: the system can work 24/7." Explain why this earns no mark, and give one disadvantage to the employees.2 marks
  9. A corridor light switches on when movement is detected. It switches off when no movement has been detected for 120 seconds. The microprocessor uses a timer that counts in seconds. Movement is detected at 0 s, 50 s and 130 s, and not again. (a) State the time at which the light switches off. (b) Describe how the microprocessor uses the sensor data and the timer to decide when to switch the light off.5 marks
  10. A farm waters a field automatically. A moisture sensor is in the soil. A water valve opens when the reading is below 35. It closes when the reading is 60 or above. For any reading in between, the valve stays as it is. The valve starts closed. Seven readings in order are 41, 35, 34, 52, 60, 58 and 33. (a) State each reading at which the valve changes, and whether it opens or closes. (b) Describe how the microprocessor and the actuator make the valve open. (c) Give one disadvantage of this system to the farmer.7 marks
  11. State what is meant by robotics.2 marks
  12. A student writes: “Robotics is a robot that copies human actions.” Explain what is wrong with this.2 marks
  13. Give three characteristics of a robot.3 marks
  14. A student says that every robot uses artificial intelligence. State whether the student is correct and give a reason.2 marks
  15. State what is meant by a microprocessor.1 mark
  16. A domestic robot must stop before it hits a wall. Give one suitable sensor for the robot to detect that the wall is near.1 mark
  17. A warehouse replaces some workers with robots. The manager says: “The robots do not need to take breaks.” Explain why this is not an advantage to the workers.2 marks
  18. A robot stops if an object is less than 15 cm away. Its sensor continually sends digitised data to the microprocessor. Describe how the microprocessor and an actuator stop the robot.4 marks
  19. A hospital uses a robot to carry medicines between rooms. The robot must stop if a person is less than 50 cm in front of it. A student describes how this works: “A motion sensor sends data to the microprocessor when it detects a person. The microprocessor checks that the person is less than 50 cm away. An actuator then displays a warning on the robot's screen.” Identify four mistakes in the description and correct each one.4 marks
  20. A farm uses a robot to carry boxes of fruit along a path. The robot stops if an object is less than 40 cm in front of it. It moves again when the object is 40 cm or more away. (a) Explain how the sensor, the microprocessor and an actuator work together to stop the robot and to move it again. (b) The data received gives a distance of exactly 40 cm while the robot is stopped. State what the robot does and give a reason. (c) Give two disadvantages of the farm using the robot.9 marks
  21. AI is a branch of computer science. State what AI deals with.1 mark
  22. The syllabus limits AI systems to two types. One is an expert system. Name the other.1 mark
  23. An expert system has a knowledge base, a rule base and an interface. Name the fourth component.1 mark
  24. State what is meant by machine learning.1 mark
  25. A translation program uses AI. Give three characteristics of AI.3 marks
  26. A heater switches on at 06:00 every day. It follows this one fixed instruction and never changes what it does. A student says the heater uses AI. State two characteristics of AI that the heater does not show.2 marks
  27. A bank uses an expert system to help decide whether to lend money. State the component the inference engine searches for similar knowledge, and the component it then applies that knowledge to.2 marks
  28. A music app recommends songs. After each recommendation it records whether the user played the song or skipped it, and uses this to change what it recommends next. Explain how this is machine learning.3 marks
  29. A garage uses an expert system to find faults in cars. A mechanic inputs two facts: the engine will not start and the lights do not work. The system then asks: 'Is the battery more than five years old?' Asked to explain how the system finds the fault, a student writes only: 'It has a knowledge base, a rule base, an inference engine and an interface.' Write an answer that would earn 4 marks. Include why the system asked about the battery.4 marks
  30. A greenhouse is watered by a computer system. No person is present. Each day the system records how much water it gave each plant bed, and a reading of whether the soil was too dry, too wet or correct the next day. One designer suggests an expert system. Another suggests machine learning. Explain why an expert system is not appropriate here (2 marks), and explain how the system could use machine learning to improve its watering (4 marks).6 marks

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