Here is my latest build 😀
The Copter :
The copter is a large one of my own design made from lightweight CF rods, equipped with a brushless gimbal. I am using very efficient low-kV pancake motors and large (17” props) with Panasonic NCR18650B cells in a 4S5P configuration. My target AUW is 2kg.
The Lynxpilot Flight Controller:
The quadcopter runs on a hybrid linux flight controller called LynxPilot, which I’ve designed myself. I had been experimenting for many days with a pcDuino , a 1GHz board with an ARM SoC which worked great for my purposes. But with it came the problems of running timing-intensive operations on Linux. Due to the non-realtime nature of Linux this was especially problematic. To work around this I patched the ‘linux-sunxi’ kernel sources with a RT-PREEMPT patch and got the realtime kernel running on my board. This took a long time since the kernel sources were hardly documented and also obsolete to some extent.
The software running on the board was my next consideration , since I couldn’t decide whether to port AP_HAL over to it or write my very own. In the end I decided to write my own. Now, I already had a spare APM 2.5 and i thought, why not use it as a slave for a robust autopilot system. I went ahead on this angle and ended up with running the computationally intensive algorithms (EKF , etc.) on the pcDuino while using the APM to get raw sensor data and R/C inputs and shoot it over a UART to the pcDuino. I was inspired by El Gallinazo’s work (http://gallinazo.flightgear.org/) to do this.
I had decided to use the APM for controlling the ESCs too, but I got some AfroESCs which are awesome and allow me to use i2c to control the motors. I ported a firmware patch (https://github.com/balrog-kun/tgy) to the latest version of SimonK which allows me to use the ESCs to get motor RPM feedback back to the flight controller allowing for major improvements in stability. My code is yet to implement this as of now as I still haven’t tested the firmware on the Afros (ordered some from HK). I presently use a very limited set of Mavlink parameters for telemetry, but will expand this in the future. Telemetry will be run via the same radio as below – the Ubiquiti Rocket M5
High Definition FPV:
I’ve been successful in streaming low-latency video over my wifi network using a crappy webcam and the pcDuino, so I decided to expand the same system for the downlink as it had worked well for me. I’m using the below equipment for the high-definition link.
2 x Ubiquiti Rocket M5’s – Air side one will be decased and carrying 2x cloverleaf antennas [lighter that a Bullet with a heavy N-Type connector at 85 grams]
1 x Logitech C920 webcam – has hardware H.264 encoding which means the pcDuino can just route packets without any computation required for encoding the video stream.
Current status of the project is that I’m waiting for the motors props and ESCs to arrive. I still don’t have the funds required to buy the Ubiquiti Rocket M5 pair and the 20 NCR18650B cells. If you would like to help me out with any contribution ($ , parts, or otherwise) you can email me at firstname.lastname@example.org
THANKS FOR READING!!