Duration: Jan 2020 - Mar 2020
Purpose: This project was executed at the UAV Lab, Indian Institute of Science, Bangalore
As we started testing more complex autonomous applications, we needed more processing, more flight time, more sensors. The drones we had just weren't cutting it. Under the weight of an NVIDIA Jetson Nano, a 6000mAh battery, a camera and a laser, they were either struggling to get off the ground or running out of power very fast. The only one capable of carrying all this was an S500, but there wasn't enough space to comfortably mount the bulky and expensive Nano. So we decided to build our own drone to our custom specifications.
Requirements
The S500 had a maximum takeoff weight of 1.8kg, beyond which performance would suffer. We had about 1.2kg worth of electronics including motors, ESCs and battery to put on the drone.
In order to use the same motors, we needed to increase the size of the drone while maintaining it's payload capacity and maximum takeoff weight, which meant our frame had to be under 600g.
Design and Fabrication
We designed a frame with downward facing propellers as they gave us a three-fold benefit:
Pushers offer marginally higher efficiency as compared to conventional upward facing propellers
With a wider frame and no obstructions, we were able to use the larger propellers for our motors
Downward facing propellers allowed a large mounting space on top of the drone, where multiple sensors, processors and other components could comfortably be placed
The design was laser cut into Birch wood and assembled, the final configuration weighing only about 400g.
We found that the supporting square guard alone weighed close to 200g, so we got rid of it and applied a carbon fiber lay up to the wood instead for strength.
The resulting frame weighed only about 450g.
With all electronics onboard, the takeoff weight of this drone was 1.7kg.
Finally, it was time to test.
We managed to comfortably carry larger processors and extended the flight time from about 7 min on the S500 to about 12 min on the new drone.