6a: Simulators slides |

Simulators

• Software to allow work even without actual robots

• For ROS they implement a series of nodes that pretend to be a robot
  • publish topics that a robot would publish (e.g. /odom)
  • Subscribe to topics that a robot would (e.g. /cmd_vel)
  • Uses a “physics engine” to simulate what would happen in the real world

• Simulator creates the 3d world

  • Maintains an imaginary x,y where the robot is right now
  • Uses 3-d dynamic model of the robot
  • Has 3-d models of obstacles like walls
  • Changes all these states based on motion commands it receives
  • Of course, much more complex
• Gazebo is a complete simulation environment
  • Really sophisticated 3d simulator plus visualization
  • Can simulate all kinds of things not just our robots
  • I have seen Gazebo models of a complete Amazon Warehouse Floor
  • With multiple Robots running around
• RViz can only visualize data in 3D but it is not the source of the data
  • While it looks similar, it is not a simulator
  • It “simply” visualizes topics that it subscribes
  • In a 3-d space