Raspberry Pi inspired autopilot

http://www.emlid.com/

by ivereninov • 12 years ago

110 59 12 years ago

Jeandon• 12 years ago

Looks very nice. Is Linux actually real-time enough to run autopilot code?

klinquist3• 12 years ago

Typically, APM/MavLink runs on a Arduino (my Quanum CX-20 quad runs an Mega 2650). This looks like this is a Raspberry Pi shield that I suspect contains an ATmega - so it's not Linux that is doing the flight controlling.

ivereninov3• 12 years ago

Actually we run APM code ported to Linux, there is no Atmega on the board. There was a lot done to make this possible including special real-time Raspbian. It flies very stable and with great timing performance.

CHY872• 12 years ago

Possibly not. It seems that this runs APM, which is an open source autopilot system. On their install pages, the Raspberry Pi is listed as a companion computer (presumably to be hooked to some other device that runs the code) (which this system might not do) but the Beaglebone Black (which I guess is similar to the Raspberry Pi, so might be what they do here) requires installation of realtime patches for Linux.

This works by patching the Linux kernel to make almost all of it preemptable, (replacing spinlocks with mutexes) so interrupts can be acted on more quickly.

ivereninov3• 12 years ago

We run APM on Linux. The port to Raspberry Pi is our effort and it is now supported in APM upstream.

pjc502• 12 years ago

It's fast enough in almost all cases to work. "Realtime" is more about proving worst-case bounds on all control loops.

lovelearning2• 12 years ago

They are using a realtime patch on Raspbian. [1]

They also say "autopilot’s code works directly on Raspberry Pi using the APM’s Linux HAL". [2]

[1] http://www.emlid.com/raspberry-pi-real-time-kernel/ [2]: http://www.emlid.com/navio-apm/

asynchronous132• 12 years ago

Yes. Linux is plenty fast to run autopilot code. There are real-time patches for Linux kernel, but in my experience those are not necessary for decent performance.

valarauca12• 12 years ago

A true real time system is likely over kill.

General time-sharing systems generally are accuracy to +/- 4ms. Which is acceptable for most applications, as 60fps is ~16ms per frame.

If you (ab)use Linux properly you can get most your threads to only halt on blocking for IO. So they'll get scheduled practically (not always) once that IO state is satisfied.

This requires heavy multi-threading not horrible, just isn't amazingly optimized for cache.

I control high pressure fuel systems and we don't need to use Real Time OS's (always), and generally sigh away from them when I don't.

lsaferite• 12 years ago

I would guess the PID loop benefits greatly from real-time execution. So much so that really the base control system should be on a dedicated controller with AP functionality as a secondary system driving the inputs to the PID controller.

MegaDeKay• 12 years ago

The second PDF in the link below compares the Raspberry Pi with the Beaglebone Black for a next gen APM. The nod went the the Beaglebone because of more GPIO, PWM support, and the two PRUs for realtime operation. The Pi B+ helps the first point, but not the other two. There is also a really interesting page in here on the latencies that are required.

BTW, this was written by Andrew Tridgell of Samba fame.

http://diydrones.com/profiles/blogs/a-peek-into-the-future-o...

2bluesc• 12 years ago

Thanks for this. Whenever I see people running around high fiving over the Raspberry Pi, I start to formulate an argument how the BBB would almost always be vastly superior for slightly more cost.

klinquist3• 12 years ago

Using the RPi as a video encoder may be the "killer app" for this. Currently, there isn't a "ready to fly" solution that will encode video and send it out over LTE.

ivereninov3• 12 years ago

Exactly! We are working on this and will include a very easy to use LTE streaming configuration for HD FPV experience.

shoggs• 12 years ago

Is it actually possible to fly FPV with that much of a delay?

spiritplumber• 12 years ago

You can use an Android phone with a Propbridge or IOIO board for control (disclaimer: I make and sell the Propbridge), however that is fairly heavy and contains components that you don't particularly care for, like a screen.

That said, I had 2G video off a flying wing in 2010 with this method.

bhhaskin2• 12 years ago

This is awesome! How much weight does it add compared to traditional autopilots?

igorvereninov5• 12 years ago

Thanks! Additional 23 grams for raspberry pi A+

bhhaskin2• 12 years ago

Not bad at all considering all of the extra processing power.

mjs7231• 12 years ago

Just curious here. The CC3D boards were also open source, hackable, and only 1/3 the price, and guessing, but looks about 1/5th the size. What makes using better than all those downfalls?

igorvereninov5• 12 years ago

This is completely different. Autopilot runs under Linux and that gives incredible flexibility. You can send HD video over LTE, run scripts in flight. SSH to drone in the air, how cool is that?

Phlarp3• 12 years ago

How is running scripts (locally?) or SSHing into it over a serial modem any different from the scripting functions or telemetry information available with APM or GCS (CC3D) based systems?

What advantages would the raspi have in streaming HD video over LTE that strapping last years android phone to the drone wouldn't give me?

eots• 12 years ago

Yes, SSH-ing to my drone and running scripts while doing low passes and tight turns is just what I need. Sarcasm aside, this looks really cool from a hacker perspective but I'm straining to find a practical use case. Both CC3D and Naze32 platforms are open (hardware and software), smaller in size, cost 5 times less -- but are, I guess, nowhere near as flexible as this thing.

georgemcbay2• 12 years ago

Not sure how different it really is.

I have to admit, as someone who is into quads (and embedded software) my first thought was that it would be cheaper to buy a $35-60 CC3D or knock-off dedicated APM module and then just add a Raspberry Pi to the quad as a separate unit. Having the two communicate is a bit more complicated but totally doable via serial if you're willing to hack on APM or OpenPilot code and a lot of the use-cases people are bandying about don't actually need the two units to communicate anyway.

NietTim• 12 years ago

I have thought about doing this before, but figured this would be too heavy. Guess I was wrong, very cool!

nakedrobot2• 12 years ago

Is this only 8-bit? That is not really responsive enough.

Currently the best-in-class are naze32 with baseflight/cleanflight firmware (stunt, mini copters) or APM / pixhawk (mapping, cinematography, GPS)

igorvereninov5• 12 years ago

It runs on 32bit ARM at up to 1GHz with 512MB of RAM. Completely different league.

Quai• 12 years ago

APM is powered by a 8 bit controller.

tomswartz07• 12 years ago

This is very neat!

Has there been any thought about using the 'Compute Model' RasPi? It's the RasPi in the DIMM form factor. Perhaps this would help lighten up the payload even more?

mavkhimenia7• 12 years ago

Thanks! We've been thinking of it, but rejected the idea. RPi A+ is quite light, so RPi+Navio weighs as the normal autopilot. Also, A+ is much cheaper.

scoot• 12 years ago

RPi A+ is quite light, so RPi+Navio weighs as the normal autopilot

Not to detract from the novelty value of an RPi based flight controller, but if you were involved in the design, you must know that's just not true:

RPi A+: 23g, Navio: 24g, Total: 47g

APM Mini: 7g

That's a significant difference in a situation where every gram counts towards flight time.

The Navio also costs 6X an APM mini, and that's before you add the RPi and power module, which brings it to 8X.

I get why someone might develop this as a hobby project, but I can't think why anyone would buy one.

Alupis2• 12 years ago

For those looking at the pictures and thinking "that's not a Raspberry Pi!", it is... under the black Navio+ board is a new Raspberry Pi model B+[1]

[1] http://www.raspberrypi.org/products/model-b-plus/

gadders• 12 years ago

When I read things like this, it always reminds me of the Kiwi chap that was trying to build a cruise missile in his garage [1]. Although this is smaller than what he had planned, I would imagine you could add a "release" functionality to the Pi Autopilot so it could drop something when at a certain position.

[1] http://aardvark.co.nz/pjet/cruise.shtml

Alupis2• 12 years ago

That's called a "Drop Box"[1] and they're fairly common. You just need a spare servo to operate the bay door.

[1] http://www.hobbyexpress.com/senior_telemater_plus_drop_box_1...

tomsunax• 12 years ago

Bruce is very much into quadcopters and other hobby-rc stuff these days. Check out his YouTube channels if you want to see more of him, quite informative

https://www.youtube.com/user/RCModelReviews (educational)

https://www.youtube.com/user/xjet (fun stuff)

pjc502• 12 years ago

Ssh, this is going to happen sooner or later and result in quadcopters being banned forever. :(

zo12• 12 years ago

How much hacking and/or electronics knowledge is required to set this up and get it running?

#Edit. Another question, will the Reach (when it comes out) integrate easily with the boards coming out in Februaray, and be supported as part of Navio+?

VereninovIgor2• 12 years ago

Not much. Write an SD card image, install APM, connect to Wi-Fi or Ethernet and you are ready to go. After that it requires calibration and setup in APM Planner like any other autopilot.

Reach will be a replacement of normal GPS for any autopilot. It will be compatible with Navio+.

simpsond• 12 years ago

I'm somewhat intrigued by the HAT spec and how the daughter card provides the OS a device tree fragment. Can you comment on the pains/gains from conforming to it?

igorvereninov5• 12 years ago

Did not help us much(since we are working with spidev and i2cdev), but did not cause much trouble either.

nacnud• 12 years ago

How do the power requirements for the autopilot compare to that of the rest of the flight hardware?

asynchronous132• 12 years ago

miniscule. The electronics will consume a few watts, the main motors will consume several hundred watts.

Raspberry Pi inspired autopilot

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