RASPBERRY PI BASED QUADCOPTER
OVERVIEW
This Raspberry Pi based quadcopter was built using the Emlid Navio2 flight control board. Automatic flight was successfully implemented using QGroundcontrol's mission planning capability.
MATERIALS
This quadcopter was designed with the intention to carry lightweight camera a payload. The design uses a 2200 mAh LiPo 4 cell battery to power flight supporting a carbon fiber airframe.
The flight control board was selected from among many options. Since autopilot was the goal, the Emlid flight control board containing on board GPS and dual IMU's was selected.
FLIGHT TIME MODELING
Using open source drone modeling software developed by MIT CSAIL I was able to calculate the flight time corresponding to a drone using a 2200 mAh battery and 10 inch propellers with a weight of roughly 2.8 lbs, which was 12 minutes and 20 seconds. There was considerable design margin for flight time since the total design weight of all my components was roughly 1.3 lbs.
FLIGHT CONTROL
Q Ground Control was used to connect to the drone for mission planning and configuration. This program uploads Mavlink based mission configuration files to the drone to instruct the drone on what flight modes to use. For autopilot, Q Ground Control can be used to upload autopilot mission instructions to the drone.
CHALLENGES
Co-site interference between the flight control radio and components such as magnetic sensors and the GPS receiver presented challenges to the IMU. After adding a metallic ground plane beneath the GPS antenna, GPS performance improved significantly. In addition, swapping out the original on-board radio for a less interfering option improved the accuracy and stability of all on-board sensors.
Magnetic Interference Prior to RF Shielding
The data plot on the left shows measurements for magnetic field strength in 3 dimensions. Prior to installing RF shielding between the on-board radio and IMU, magnetic variation was significantly higher than acceptable, as indicated in the plot to the left. High magnetic field noise reduced EKF (Extended Kalman Filter) accuracy and therefore limited guided flight capability.
Magnetic Interference with RF Shielding
The data plot on the left display measurements for magnetic field strength in x-y-z dimensions after installing RF shielding between the on-board radio and IMU. Magnetic field variation was significantly reduced after adding RF shielding between the flight radio and the IMU.
Flight Test
The videos to the right and below contain flight test footage from the automatic flight test performed in February 2022. A happy landing!
Flight Test Recording
This video shows the measured flight locations over the course of the flight shown above.