Crazyflie Leader Follower System

This is an implementation of a leader follower system based on a linear consensus protocol for maintaing formation.

Built under the mentorship of Dr. Vishwesh A. Vyawahare & Ms. Ritika Thusoo @ Robotics Lab, Ramrao Adik Insitute of Technology.

demo video

leader-follower-demo.mp4

how does it work?

• Each follower drone is assigned a transform function that calculates its position based on the leader's position.
• The Leader Drone is controlled via the operator via a REST API.
• The Leader Drone communicates command and it's position via the websocket which all followers have subscribed to.
• The followers receive the leader's position and calculate their own position based on the transform function and execute it.

how do I use it?

IMPORTANT: You will need to have as many crazyradio dongles as the number of drones you want to control.

setup

(optional) create virtual environment using python3.8

# using conda
conda create -n lfdemo python=3.8

# using venv
python3.8 -m venv venv

Activate Environment

# using conda
conda activate lfdemo

# using venv
source venv/bin/activate

install dependencies

pip install -r requirements.txt

running the system

1. Start the Leader Server

python leader.py <LEADER_URI>

Replace <LEADER_URI> with the URI of the leader drone. For example, radio://0/80/2M/E7E7E7E7E7

Wait until the server is started. You should see a message like this:

INFO:     Uvicorn running on http://0.0.0.0:8000 (Press CTRL+C to quit)

2. Start the Follower Server you can repeat this for each follower you want to add to the swarm

python follower.py <FOLLOWER_URI> <TRANSFORM_FUNCTION>

Replace <FOLLOWER_URI> with the URI of the follower drone. For example, radio://1/20/2M/E7E7E7E7E7 Replace <TRANSFORM_FUNCTION> with the function name from formations/__init__.py. Refer to the resources section for creating your own transform functions.

example

5 drones with ids 10-50, 10 being the leader and the rest being followers.

# Terminal 1 (leader)
python leader.py radio://0/10/2M/E7E7E7E7E7

# Terminal 2 (follower 1 - right position)
python follower.py radio://1/20/2M/E7E7E7E7E7 right

# Terminal 3 (follower 2 - left position)
python follower.py radio://2/30/2M/E7E7E7E7E7 left

# Terminal 4 (follower 3 - behind position)
python follower.py radio://3/40/2M/E7E7E7E7E7 behind

# Terminal 5 (follower 4 - front position)
python follower.py radio://4/50/2M/E7E7E7E7E7 front

resources

creating a transform function

All the transform functions are defined in formations/__init__.py. You can create your own transform function by adding a new function to the file.

Here is an example of a transform function that calculates the position of a drone to be in diagonally in the front to the right of the leader drone.

def front_right(leader_position: dict):
    new_position = {
        'x': leader_position['x'] + 1,
        'y': leader_position['y'] + 1,
        'z': leader_position['z']
    }
    return new_position

endpoints

1. Take Off

POST http://localhost:8000/takeoff

This will make the leader and all connected followers take off to a height of 1 meters.

2. Land

POST http://localhost:8000/land

This will make the leader and all connected followers land.

3. Set Position

POST http://localhost:8000/setpos
{
    "x": 1,
    "y": 1,
    "z": 1
}

This will set the leader drone's position to the specified coordinates. The followers will adjust their positions accordingly.

4. Shutdown

POST http://localhost:8000/shutdown

This should be run after the drones are landed. This will close the links between the server and drones.