Resources for Using Bitcraze Crazyflie Drones with Qualisys Systems

Qualisys motion capture systems can provide high-speed, reliable, precision position tracking for the closed-loop control of Bitcraze Crazyflie quadcopter systems. This repository contains a collection of resources for developing Crazyflie projects and related applications that interact with QTM.

Setup Instructions

• In QTM, the rigid body that corresponds to the Crazyflie quadcopter should have custom Euler angle definitions:
  • First Rotation Axis: Z, Positive Rotation: Clockwise, Name: Yaw, Angle Range: -180 to 180 deg.
  • Second Rotation Axis: Y, Positive Rotation: Counterclockwise, Name: Pitch
  • Third Rotation Axis: X, Positive Rotation: Clockwise, Name: Roll, Angle Range: -180 to 180 deg.
• The capture rate should be 100 Hz.
• The Crazyflie USB radio dongle must be set up correctly.
• The Crazyflie drone should be placed on the floor, visible to the cameras, with the front of the Crazyflie pointing in the positive x-direction of the QTM coordinate system. (Important: If the front of the drone is not aligned with the x-direction it may lose control and crash. The stability of the closed-loop position control algorithm is predicated on correct initial alignment.)

Python Script Examples

NOTE: The scripts are currently deprecated as they use an older version of the Qualisys Python SDK.

The example Python scripts in this repository are intended to serve as a starting point for implementing custom Crazyflie applications.

All scripts have been tested with Python 3.6.4 running on Windows 10 in a conda environment.

Dependencies

• cflib
• qtm
• xmltodict

Caveats

Albeit small and lightweight, the Crazyflie drone may damage itself, along with objects and people in its vicinity upon contact. Please be mindful of the surroundings and remember that a motion capture / position tracking system does not necessarily provide facilities for collision avoidance.

Additionally, while controlling Crazyflie drones programmatically using a Qualisys motion capture system, please be aware of the following issues:

• Running the control loop that issues send_setpoint() commands to the Crazyflie while no position information is relayed (via send_extpos()) may cause the drone to fly uncontrollably and crash. The control loop that issues commands to the Crazyflie must be stopped before stopping streaming from QTM.