crazyflies-Package

Crazyflie and Safeflie Classes

If you want to start scripting your own application logic, you can use the crazyflies package to create a Crazyflie or Safeflie.

The Crazyflie and Safeflie classes are examples of how to use the underlying interface to control a Crazyflie, they use the crazyflie interfaces package to do so. It is the easiest way to start implementing your own logic. A Crazyflie/Safeflie will automatically call the gateway to establish a Crazyflie connection.

If reduced functionality is required, it is recommended to use the Client classes to implement only parts of the communication on the application layer. This is especially important when using many Crazyflies to limit the number of ROS Topic connections.

The following class diagram shows the Crazyflie and Safeflie classes and how the user can interact with them.

Note

The ds-crazyflies repository tries to provide a universal framework for crazyflies. For a more detailed but therefore also more use-case specific example on how to use ds-crazyflies also check out the Pad Swarming repository. The repository allows to fly up to 50 Crazyflies equipped with QI-Charges.

Safeflie

A big problem of the high level commander inside the crazyflie is the limited supported update rate when sending go_to commands. These should ideally not be sent out with more than 1Hz. The Safeflie tries to mitigate this by using the high level commander only for takeoff and landing, while during flight the low level command cmd_position is used. This however has to be sent continously while flying and the transitions between the two command modes have to be handled carefully.

State machine of safeflie

The Safeflie allows to safely switch between the high level commander and the low level commander. It provides 3 topics:

  • safeflieID/takeoff

  • safeflieID/land

  • safeflieID/sendTarget

With takeoff and land the crazyflie can be started and stopped (they are of the type std_msgs/msg/Empty). During flight, targets can be sent using the sendTarget topic:

SendTarget.msg
geometry_msgs/Point target # Target position

Start your first Safeflie

Make sure your Webots instance is running with the crazyflie you want to connect to. Also make sure the framework.launch.py is running.

Then in a new terminal you can start a Safeflie with:

ros2 launch crazyflies safeflie.launch.py id:=0 channel:=100 initial_position:=[0.0,0.0,0.0] type:=2

  • id: The id of the crazyflie.

  • channel: The channel of the crazyflie, if a real crazyflie is used.

  • initial_position: The crazyflies initial position, if a real crazyflie is used.

  • type: 1 if you want to connect a hardware crazyflie. 2 if you want to connect a webots crazyflie.

For webots crazyflies only the id is necessary.

Note

The safeflie automatically adds the crazyflie to the appropriate gateway (hardware or webots) when instantiated. Do not add the crazyflie with rqt or service call before instantiating the safeflie.

Class diagram of Crazyflie and Safeflie

Note

Not shown in the diagram are the connections of the Crazyflie with the underlying software stack.

Crazyflie class

class crazyflies.crazyflie.Crazyflie(node, id, channel, initial_position, type)

Bases: ConsoleClient, EmergencyClient, GenericCommanderClient, HighLevelCommanderClient, LoggingClient, RPYTCommanderClient

Represents a crazyflie.

Allows user to interchangeably use different crazyflie implementations (currently Webots or Real Hardware)

Parameters:

  • node (rclpy.node.Node)

  • id (int)

  • channel (int)

  • initial_position (List[float])

  • type (CrazyflieType)

Safeflie class

class crazyflies.safeflie.Safeflie(node, id, channel, initialPosition, type)

Bases: Crazyflie

Parameters:

  • node (rclpy.node.Node)

  • id (int)

  • channel (int)

  • initialPosition (List[float])

  • type (CrazyflieType)