Return of the Lawn Dart (Inav autonomous)

[Try-n-glide]

Having originally set out to build an Rcandy rocket plank glider....
http://forum.flitetest.com/showthread.php?36156-Rocket-plank/

I ended up with something totally different.


The plane which I renamed the lawn dart ( because it was not a plank as originally planned ) now has an INav flight controller. With a few flights under his belt and a lot of work programming and learning a new system I have a very cheap fully stabilized, and GPS powered autonomous flight modes ( loiter and return to home).

All of this started when I pulled a $10 closeout clone F3 EVO quad flight controller out of a box and thought: What can I do with that?

It turns out you can do quite a bit these days. Betaflight has been reprogrammed as Inav which is very useful for fixed wing with a cheap $20 GPS unit (ublox m8n) as seen on the wing it has fully autonomous flight modes. I have tested and confirmed that programmable flight stabilization, loiter mode, and automatic return to home all seem to work quite well with some tinkering. You can literally flip a switch on the Taranis and it will fly in a circle maintaining altitude without pilot imput, or Fly back to the spot where it was armed and circle.

Future tests will be flying a pre-programmed route without pilot imput, and auto land at home without input. Pretty cool so far. Check out the painless 360 series on YouTube for more information about what Inav can do.

If you start out with an SBUS or CPPM plane you can add all these features for $30 or $40 worth of parts. Actually a whole lot more features that I haven't even scratched the surface of.


Fun!

 

[ElectriSean]

iNav is sweet, on the list of maidens this spring I have a FX-61 wing running iNav But seriously dude, one picture? Can't hardly get by on just one

 

[Try-n-glide]

iNav is sweet, on the list of maidens this spring I have a FX-61 wing running iNav But seriously dude, one picture? Can't hardly get by on just one

oh yeah pictures! My wing design flies well. It is beat up these days from testing varies CG etc. it lands too flat and beats up the nose. I'd love like to increase efficiency for longer flights also.



Yes, Inav is really incredible and powerful. Also a real head scratcher. But that is no surprise in the RC hobby these days and it is free after all. The things that can be done from settings for teaching a total newb to fly (altitude hold and bank angle limits, to auto righting when sticks are released, auto land, etc) along with advanced GPS options are really cool. Plus it is so cheap! A $15 xsr receiver plugged into most any cheap FC board (there is a list of Inav compatible FCs on the Inav wiki) will implement all the non-gps options.

If there is any interest on the forum I will post some vide of return to home.

 

[rockyboy]

Yes yes yes! :applause:

We need video and some more detailed info on how you've wired things up, configurations in iNav & the Taranis, etc. and links!

I've been interested in doing this for a long time but haven't taken the plunge cause of the lack of documentation I've found so far.

 

[Try-n-glide]

Rockyboy there is so much going on to learn Inav that it will take a few posts. I'll try the first few steps, and give some direction. There is WAY more after this trust me, but the hard parts are mostly covered:

Let's watch Ragthenuttsoff's (Matt) into to INAV and see what Inav can do!! https://youtu.be/1DCCjPbHl_I

1) Buy an Inav compatible flight controller board. Not every board is. See the list at the Inav Wiki:

https://github.com/iNavFlight/inav/wiki/Supported-boards

2) Next it's time to download the Inav configurator from the Google Play webstore - don't worry it's free.



EDIT: Google App version does not support all features. Download full desktop version here: https://github.com/iNavFlight/inav-configurator/releases

3) After you have a board you have to install the Inav firmware on the board using the Firmware Flasher function on the Inav Configurator. Luckily flashing firmware is the same as Betaflight which is well covered on Youtube - because if all of the correct drivers are not set up on the computer you can't do it. This Joshua Bardwell video is excellent for getting into "DFU" mode, which is required to flash drivers:

https://youtu.be/m4ygG6Y5zXI

Boards are flashed with USB to micro USB cable. Plug USB into computer, hold down the "bootloader" button (or if absent jumper the bootloader pads with a wire) while inserting the micro usb into the FC.



If all goes well you see DFU appear in the box - DON'T hit connect just yet!! Click on the Firmware Flasher tab off to the left.

Next choose your exact board, a firmware version (most recent or if that gives you problems try other versions later) then load firmware online, and hit flash firmware.



If all goes well you now have Inav firmware on your board. Congrats!!

Now pull the plug and plug it back in. Go back to the welcome screen with the tab on the left, and click the big blue CONNECT.

You should now see this screen:



You now have the ability to configure your board using the INAV GUI. Or if you are brave you can use the CLI "command line interface" tab and configure the board with command lines just like MS-DOS ! https://github.com/iNavFlight/inav/blob/master/docs/Cli.md

4) Let's take a step back, and connect a FrSky XSR SBUS receiver to our board. Get out your magnifying hood, jewelers loop, or hope you have 25 year old eyes. And sharpen you soldering skills - no globs and no bridging allowed. Here is an example of how to wire the XSR (Notice the CPPM and Telemetry wires aren't in use - you can cut the CPPM wire off. The Telemetry wire can be used but I haven't gotten there yet):



Different boards have different "UART" ports to wire in the receiver. Refer to wiring diagram for yours. This board also requires you to jumper a TINY connection to choose either SBUS or CPPM.

5) Once soldered up connect your board back to INAV because we need to configure Inav to talk to the receiver. It should power up the receiver. If not your board requires a BEC be wired in first to power the UARTS. At this point bind the receiver.

Then go to "Ports" tab on the left column and you have figure out which UART your receiver is connected to (see wiring diagram for FC) and slide the "SBUS" tab over on that UART.



Here you see that UART 2 is the receiver port, and notice UART 3 is hooked up to my GPS. Hit SAVE AND REBOOT otherwise all that tab sliding is for nothing. Save your work.

You aren't done just yet. Next you have to go to the configuration screen:



Hey look we've chosen Flying Wing as the model type and the picture tells you which PWM outputs on the FC go to which control servos and or ESC - but I digress because we are still setting up the receiver. Scroll down the the receiver setup box.



Now it's time to select Serial Based Receiver, and SBUS in box 2. Don't forget to SAVE AND REBOOT.

If you have done all of the above work correctly you can now go to the receiver tab and verify that your radio signal is getting to your FC. Here is the good news - NO MIXING. This is a standard 4 output control setup and INAV does all of the mixing for you. So verify your sticks move the correct slider on the receiver tab.



_________________________________________________________________________________

Wow, that's a lot of typing for tonight so let's end there for now. Too much reading? Head on over to Youtube and watch Painless360's complete INAV series:

8 whole videos with lots of info: https://youtu.be/T_4ph-YCnaA

 

[rockyboy]

Awesome write up! Thank you!

I'm itching to dig around in my junk drawer for an unused F3 board and order a GPS module now.

From your experience, do you suggest setting this up on a 'beater' airframe first to get comfortable with how it works before trying it on a 'nice' plane?

 

[Try-n-glide]

Awesome write up! Thank you!

I'm itching to dig around in my junk drawer for an unused F3 board and order a GPS module now.

From your experience, do you suggest setting this up on a 'beater' airframe first to get comfortable with how it works before trying it on a 'nice' plane?

That's pretty much what I did. You don't absolutely have to because in the modes tab on Inav you will find a "Manual" mode (aka "passthrough). This means that the board can be configured as a mixer only, but none of the auto stabilization or gps settings affect the plane. So you can fly it as normal and the switch to stabilized or other modes in the air with (hopefully) enough altitude to switch back.

However I think it makes a lot of sense to simply put it on a leftover FT foamie or similar. That way you can learn the details of FC orientation (the board really needs to be front directly forward - level, well not dead level because if you put the nose of the board a couple degrees down you will have slightly positive AOA when the board tries to level you) test features such as auto launch, auto land, failsafe settings, and GPS settings without fear of losing an expensive airframe.

A couple of more hints:

Your plane will NOT arm unless all of the check boxes are green on the initial screen (see the picture above with the box that says "back"? Off to the right are the arming check boxes - my gps boxes are red in the pic). If any are red you have to figure out why first. Example: You MUST do a 6 way gyro calibration or it won't arm. Or if you connect GPS it won't arm unless you have a gps lock. In my case I had red boxes when I hooked up gps - finally figured out the usb will not power gps on my board - once I plugged in a flight batt and the bec powered up the board I had gps lock in 30 seconds and all green boxes.

On the configuration tab there is a safety switch: upper right hand box a slider for 'enable esc and servo ouputs'. Unless that is turned on no signal will go out to esc or servos.

Also, when you are in stabilized modes on the ground servos will barely move. This is normal. Put it in Manual on the modes tab to test servo directions and throws. Do NOT use your transmitter for servo reverse. Use the servo tab, on a flying wing one of the servos will likely be set to 60% throw (or whatever) and the other servo to MINUS 60%.

 

[RMDC]

I had no idea that this category of controlled flight was so accessible and affordable. I think this summer I'm going to build a Spear and fly that sucker to Mars.

 

[Try-n-glide]

Guys a quick update: I tried to video a return to home flight, and loiter mode. The video was crap because I was trying to hold the QX7 with one hand and film and flip switches with the other - The features worked fine, but the filming not so much.


Another thing I just learned: The Chrome App version of the INAV Configurator does NOT support flight missions. You have to download the stand alone Mac/Windows version here: https://github.com/iNavFlight/inav-configurator/releases

 

[Try-n-glide]

Confirmed able to save PID/Configs/etc on my F3 EVO from my Iphone with a Bluetooth module. Also uploaded a GPS flight mission, and confirmed it saved, but haven't tested it.

There is a free Iphone app called Mobile Flight. It is compatible with Inav (that I'm using). Also supposed to be Betaflight/Cleanflight compatible.



What you do is purchase a $10 bluetooth HM-10 module (Amazon). It has 4 wires...RX/TX for signal, and VCC (5v)/Gnd. 5v connection should be obvious. RX on the module goes to TX on an unused UART on the FC, and RX on the FC goes to TX on the HM-10.



As you can see I permanently wired in the RX/TX to the board, and use a male to male connected to an unused power pin on my PWM header for 5v power to the HM-10. The HM-10 module uses a 6 pin header with only the middle 4 in use. So 2 standard three wire servo connectors with the 2 outside wires disconnected work great. Obviously you'll need to be careful about polarity on the power wire or fry something with my setup.

I have it configured to make changes then remove the Bluetooth module - simply because Bluetooth only has a very short range, so it is not useful in flight. However - There are people with long range setups that connect this, and you have a very nice HUD on your Iphone - artificial horizon, GPS tracking on a map, etc. That would be pretty cool but I don't know how to do it.

The you configure the UART for communication......I read you need to set it at 9600 baud or it overruns the Bluetooth speed.



As you can see my Bluetooth module is connected to UART 1 on my board with the MSP turned on at 9600.


There is a thread on RCGroups. Some folks seemed to have trouble connecting. I had zero issues, connected pretty much automatically on the first try with the above setup.

So there you go guys, a nice solution for PID tuning in the field.