ptarpley
Posts: 3
Joined: Wed Feb 10, 2016 10:27 pm

Hardware required for making an autonomous airplane which is optionally controllable via transmitter.

Sat Jul 20, 2019 3:12 am

I am hoping to use a Raspberry Pi 2 with appropriate sensors to write software which will allow for some autonomous RC airplane flight. I am new to using the Raspberry Pi in general (even though I've had it for a long time).

I am a software engineer by trade, and I would like to write something which will autonomously control the aircraft in various flight modes, including simple things like wing leveling and more advanced things like return to home, etc.

I think as long as I can get the data from the sensors, and be able to send commands to the servos I'll be good, but I need some advice on how to accomplish the setup.

How would one go about setting up a system where I can have a switch on my RC transmitter which will allow me to take direct control vs. enabling the software I write on the Pi to take over? Also, I would be using fairly substantial servos (as far as RC airplanes are concerned), such as https://servodatabase.com/servo/futaba/s9470sv and https://servodatabase.com/servo/futaba/s3071hv, so I imagine there are current draw considerations to be made.

In normal RC airplane scenarios, you obviously hook servos directly up to the receiver...what does a setup look like which allows for normal/direct control via the transmitter and also autonomous control via the Pi?

I am completely new to all this, so forgive me if anything I said doesn't make sense.

Thanks for any input!

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Gavinmc42
Posts: 3415
Joined: Wed Aug 28, 2013 3:31 am

Re: Hardware required for making an autonomous airplane which is optionally controllable via transmitter.

Sat Jul 20, 2019 4:33 am

Wrong forum for concise answers.
Try DIYdrones.
https://diydrones.com/

There is one Pi guy who did it from scratch
But that is a saga and makes interesting reading if you want to know what can go wrong.

You can get hats with the nav stuff on it.
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

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omegaman477
Posts: 148
Joined: Tue Feb 28, 2017 1:13 pm
Location: Sydney, Australia

Re: Hardware required for making an autonomous airplane which is optionally controllable via transmitter.

Tue Jul 23, 2019 3:40 am

To your RC control question. The catch here is if the servos are directly connected to the Pi, and the Pi takes in the RC commands, all is good until the Pi crashes. Then you have a dead stick.

To be failsafe, you would need to allow the servos to be controlled by both the Pi and the RC receiver, with some switching logic to assert RC connection if the Pi fails, or if you request via RC channel. RC servo interfaces are simple +5V digital PWM waveforms, so a simple 2 into 1 multiplexor would be relatively simple, a couple of AND gates and an inverter for each servo chanel.

You just cant combine the Pi signal and RC signal, as when a Pi cashes the state of the I/O pins is random.

To be totally failsafe, you would use two servo's per control surface, with a mechanical linkage to give the RC servo priority. Total redundancy.

The hardware design would be fairly straight forward, the software would be the challenge.

Autonomous systems are complex at best. There are several frameworks around for these sorts of applications, I would do some research.
..the only thing worse than a stupid question is a question not asked.

ptarpley
Posts: 3
Joined: Wed Feb 10, 2016 10:27 pm

Re: Hardware required for making an autonomous airplane which is optionally controllable via transmitter.

Tue Jul 23, 2019 1:40 pm

I appreciate both of your replies! I will check out the DIY drones website, and thanks for the detailed response, omegaman477.

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