Flight¶

Initialization¶

To control the quadcopter, instantiate a Clover2 object.

from clover2 import Clover2

drone = Clover2()
# or with a specific node name:
drone = Clover2("my_drone")

Clover2 serves as a wrapper around a ROS 2 node. Upon instantiation, the node is initialized, and a background thread is launched to handle ROS 2 operations.

Useful Commands¶

Use the following methods to control the quadcopter’s state:

drone.arm()          # Arms the motors to enable flight
drone.disarm()       # Disarms the motors to stop them
drone.land()         # Commands the quadcopter to land

drone.is_armed()     # Returns `True` if the motors are armed, `False` otherwise
drone.flight_mode()  # Retrieves the current PX4 flight mode

Waypoint Flight¶

To navigate the quadcopter to a specific waypoint, use the navigate_wait() function. Specify the coordinate system using the frame_id parameter. Define the target position with x, y and z, and set the cruising velocity using the speed parameter.

The following example demonstrates the quadcopter flying at 0.5 m/s. The navigate_wait() function blocks execution until the quadcopter reaches the target coordinates, allowing the program to proceed only after the waypoint is reached.

drone.navigate_wait(frame_id="map", x=1.0, y=2.0, z=1.5, speed=0.5, yaw=0.0)

In this instance, coordinates are defined relative to the map coordinate system. To adjust altitude relative to the quadcopter’s current position, use the base_link coordinate system.

The following example commands the quadcopter to ascend 0.5 m from its current height:

drone.navigate_wait(frame_id="base_link", z=0.5, speed=0.5)

Use navigate_wait() when subsequent command needs to be executed after the quadcopter has already reached the target point.

Flight Without Waiting¶

The navigate() function operates similarly to navigate_wait(), but it is non-blocking. Once the command is sent, the program continues execution immediately without waiting for the quadcopter to reach the destination.

drone.navigate(frame_id="map", x=1.0, y=2.0, z=1.5, yaw=0.0, speed=0.5)

Use navigate() when your program needs to perform other tasks while the quadcopter is flying.

Example: Flying a Square¶

In this example, the quadcopter ascends to a height of 1 m and sequentially navigates through four points to trace a square pattern.

import time
from clover2 import Clover2

drone = Clover2()

NAN = float("nan")
square_points = [(NAN, 2), (2, NAN), (NAN, -2), (-2, NAN)]

time.sleep(1)
drone.navigate_wait("base_link", z=1, speed=1.0)

for x, y in square_points:
    time.sleep(1)
    drone.navigate_wait("base_link", x=x, y=y, speed=0.8)

time.sleep(5.0)
drone.land()

The use of float("nan") creates a special NaN value to tell the controller not to change the specific axis. The four coordinate pairs define the following sequential movements relative to the current position:

x remains unchanged, y increases by 2 m
x increases by 2 m, y remains unchanged
x remains unchanged, y decreases by 2 m
x decreases by 2 m, y remains unchanged

By following these steps, the quadcopter traces the four sides of a square. After the final waypoint is reached, the program waits for 5 seconds and then initiates landing via the land().

How to Get Current Coordinates¶

To retrieve the quadcopter’s current position relative to the map, use the get_position() function.

print(drone.get_position())

Output:

DronePosition(x=-0.2, y=-0.05, z=1.0, roll=0.0, pitch=0.0, yaw=-0.4)

How to Get Coordinates Relative to Another Coordinate System¶

You can retrieve the quadcopter’s current position relative to any available coordinate system. For instance, to get the coordinates relative to the map_aruco_1 marker, specify its name:

print(drone.get_position("map_aruco_1"))

Output:

DronePosition(x=-1.0, y=-0.2, z=1.0, roll=0.0, pitch=0.0, yaw=1.17)

The specified coordinate system name must exist within the TF tree. If the system name is invalid, or if a transformation between the quadcopter and the target system cannot be calculated, the position cannot be retrieved.