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Module 1 Quiz: Robotic Nervous System (ROS 2)

Quiz Objective​

Test understanding of fundamental ROS 2 concepts, including architecture, communication patterns, client libraries, URDF, and basic control systems.

Question 1: Architecture​

Which middleware does ROS 2 use to enable communication between nodes?

  • A) TCP/IP
  • B) DDS (Data Distribution Service)
  • C) MQTT
  • D) HTTP

Answer: B) DDS (Data Distribution Service)

Question 2: Nodes and Communication​

In the publisher-subscriber pattern, which statement is true?

  • A) Publishers wait for a response from subscribers
  • B) Communication is synchronous between publisher and subscriber
  • C) Communication is asynchronous, with publishers not knowing if subscribers exist
  • D) Only one subscriber can listen to a single topic

Answer: C) Communication is asynchronous, with publishers not knowing if subscribers exist

Question 3: Communication Patterns​

Which communication pattern is best suited for broadcasting a robot's current position to multiple subscribers?

  • A) Services
  • B) Actions
  • C) Topics
  • D) Parameters

Answer: C) Topics

Question 4: Client Libraries​

Which method is used to create a publisher in rclpy (Python client library)?

  • A) self.create_publisher()
  • B) self.make_publisher()
  • C) self.init_publisher()
  • D) self.add_publisher()

Answer: A) self.create_publisher()

Question 5: URDF​

Which URDF joint type allows continuous rotation without limits?

  • A) revolute
  • B) prismatic
  • C) continuous
  • D) fixed

Answer: C) continuous

Question 6: Quality of Service​

Which QoS policy in ROS 2 determines how many messages are kept in the queue?

  • A) Reliability
  • B) Durability
  • C) History
  • D) Deadline

Answer: C) History

Question 7: Topics vs Services​

What is the main difference between ROS 2 topics and services?

  • A) Topics are faster than services
  • B) Topics are asynchronous and unidirectional, services are synchronous and bidirectional
  • C) Topics can only send string messages, services can send any data type
  • D) There is no significant difference between topics and services

Answer: B) Topics are asynchronous and unidirectional, services are synchronous and bidirectional

Question 8: ros2_control​

Which of the following is NOT a standard interface in ros2_control?

  • A) Position
  • B) Velocity
  • C) Acceleration
  • D) Effort

Answer: C) Acceleration

Question 9: Nodes​

In ROS 2, what is a node?

  • A) A type of message passed between components
  • B) An executable that uses ROS 2 to communicate with other executables
  • C) A specific type of network protocol
  • D) A configuration file for robot hardware

Answer: B) An executable that uses ROS 2 to communicate with other executables

Question 10: URDF Elements​

What does the 'inertial' element in a URDF link define?

  • A) How the link appears visually
  • B) How the link interacts physically in simulation
  • C) The mass properties of the link (mass, center of mass, inertia tensor)
  • D) The geometric shape of the link

Answer: C) The mass properties of the link (mass, center of mass, inertia tensor)

Question 11: rclpy Implementation​

Which function is used to initialize rclpy in a Python ROS 2 node?

  • A) rclpy.start()
  • B) rclpy.init()
  • C) rclpy.setup()
  • D) rclpy.run()

Answer: B) rclpy.init()

Question 12: Actions​

What is the main advantage of using ROS 2 Actions over Services for long-running tasks?

  • A) Actions are faster than services
  • B) Actions provide feedback during execution and can be preempted
  • C) Actions use less memory than services
  • D) Actions can only be used with C++, not Python

Answer: B) Actions provide feedback during execution and can be preempted

Question 13: Package Structure​

What is the basic unit of software organization in ROS 2?

  • A) Workspace
  • B) Node
  • C) Package
  • D) Launch file

Answer: C) Package

Question 14: URDF Geometry​

Which of the following is NOT a valid URDF geometry type?

  • A) box
  • B) cylinder
  • C) sphere
  • D) pyramid

Answer: D) pyramid

Question 15: Lifecycle Nodes​

What is the purpose of lifecycle nodes in ROS 2?

  • A) To reduce memory usage
  • B) To provide explicit states and transitions for more robust applications
  • C) To speed up communication
  • D) To replace regular nodes entirely

Answer: B) To provide explicit states and transitions for more robust applications

Answer Key Summary​

  1. B 2. C 3. C 4. A 5. C 6. C 7. B 8. C 9. B 10. C 11. B 12. B 13. C 14. D 15. B