A few weeks ago, I started putting together various different quadcopter builds and comparing cost, efficiency, and lifting power. I've come up with a few builds that I think are pretty solid:
I also had two drones laying around in my dorm that I'd built the previous year, and I figured I could use those to do some tests on how long they could stay in the air with a payload of a given weight, since that would give us concrete data on what specs might or might not work.
However, to do that I needed to rewrite the flight controller I'd written previously, because the old version used rate mode - which means that the quad didn't know which way was up, and it was up to the user to make sure it stayed pointing in the right direction. To carry a payload (and eventually navigate autonomously) I needed to make the quadcopter autolevel - meaning the flight controller needs to know which way is up, and can stay pointing up (instead of say, pitched 30 degrees forward).
So for the last few days, I've been putting together a new flight controller paired with an IMU (instead of a standalone gyroscope) and trying to get that working. I had an issue that kept me grounded for about half a week where the MPU6050 (the IMU I'm using) wouldn't start up unless the Arduino Uno was plugged in through USB - I'm still not sure what exactly was causing that, but I wired it up to a UBEC and it worked fine.
Today, I flew the drone with a payload roughly the same weight as the RFID reader we'll be using - about 750 grams. The drone flew surprisingly well with the extra weight, although it was still very difficult to manage - the PID values are tuned for a drone about 750 grams lighter. Here's a picture of me trying my best to keep it in one spot (hence the facial expression):
However, I encountered an issue where it seems like the Arduino Uno shuts off randomly, while leaving the motors spinning - usually resulting in the drone flying into a wall or nearby bush. This isn't a very desirable outcome when carrying a sensor package worth almost $500, so I need to figure out what's causing that before we do any testing with it. I have a feeling it's due to a crappy solder connection on my part, so over spring break I think I'll just rebuild the whole thing and see if it keeps happening.
-Jonah Siekmann, URSA researcher