Prototype Tiltrotor Development using APM 2.5

We are a two-man team that just completed the first major phase of our yearlong APM 2.5 tiltrotor project. We wanted to keep things in the dark until we knew it had potential. Here is a quick summary, but if you’re interested in VTOL aircraft, we’d really like you to read our detailed project summary (attached PDF) and give us some feedback.

Just some of many major accomplishments include:

Design and manufacturing of a tiltrotor on a relatively low budget.

  • Utilized many free software applications to make educated design compromises
  • Utilized 3D printing to create complex flight control components
  • Slow, methodical engineering to identify problems and solutions before first flight

Stable hover with conversion to 23 m/s full airplane flight

  • Light hover maneuvering completed in STABILIZE
  • Hovering tested in LOITER
  • Thrust vector can be set at any intermediate angle and flown carefree all the way to airplane mode

Merged several significant portions of Arducopter and Arduplane software on APM 2.5 hardware

  • Heading strategies for quad and plane merged with unique tiltrotor control
  • Seamless blend of servo actuated aerodynamic surfaces, and 2 brushless motors to achieve stable flight at any speed and intermediate thrust angle

 

Tiltrotor 1 Prototype Stats:

  • All-up Gross Weight = 2.4 KG
  • Motors= 2x G15 810kv with 14 inch CF props / single 3300 mah battery
  • OGE Hover Power Required - 40 amps
  • Conversion Power Required – Thrust vector at 30 degrees from vertical 10 m/s = 20 amps
  • Airplane Power Required - 23 m/s = 30 amps

 

We have lots left to do, but would love to get some feedback to help guide us.

Here is what we have planned next:

Autonomous Flight

  •  Merge Copter and Plane navigation strategies to suit a tiltrotor.

Pixhawk

  • We’d love to incorporate the new capabilities of EKF, spline waypoints, terrain following ect someday. The APM 2.5 has not limited our development at all, and is still our bread and butter.

Tiltrotor 2?

  • We learned A LOT in a year. There are numerous things we can make better on this prototype, or improve upon with the “next generation” model. We’d like to build a bigger, better, more efficient tiltrotor with all the lessons learned. This is where we need some feedback from the community. Please read the detailed design summary (attached).

 

Of course we are not going to brag about designing a tiltrotor and NOT post a video.

 Tiltrotor_1_Design_Summary.pdf

This barley summarizes a year of work in 10 minutes.

 

Views: 9110

Comment by Giovanni Esposito on November 26, 2014 at 9:46am

Great work guys! APM Plane and copter branch integration is definitly the right way to go for me, not only for tilt wings/rotors, but for all the hybrid VTOL fixed wings. Glad to see that you are doing that so seriosly!

I bet it wasn't easy...

Comment by Doug Walmsley on November 26, 2014 at 10:11am

What I think you VTOL needs now is a ESC with feedback for RPM control.  Have you read Gerard Toonstra's Redesigning multirotor ESCs post?  Wondering if you could use Mikrocopter's ESCs.


Developer
Comment by Andrew Tridgell on November 26, 2014 at 2:07pm

fantastic work! Cramming everything into an APM2 is very impressive, and the flight control you demonstrate in the video is amazing. Thanks also for the detailed write up in your paper, particularly the description of the iterative process to develop the control code.

I'd love to see this continue and work out how we are going to support VTOL in the official releases.

Cheers, Tridge

Comment by Rob_Lefebvre on November 26, 2014 at 2:31pm

Very interesting development. And a really fun read on the paper you produced, thanks.  I haven't watched the videos yet, but I am curious to see what your pitch stability is like in various wind conditions while hovering.  This is typically the problem that tilt-rotor designs face.

It seems like you have done some very interesting work on VTOL code, and I'd love to see it.  I've been looking into doing this myself.  Your comments at the end about sharing the code...  I completely understand your situation.  As lead helicopter code developer, I've been concerned about the exact same thing.  That I do all this hard work for years, and some other helicopter vendor comes along and benefits.  However, you should understand that there is no way you could sell a system, using your Arducopter-derived VTOL code, without distributing the source code.  That is the nature of the software license.  (I could be wrong here, but pretty sure I'm not).  If you distribute the program in any way, the source code must be released.

I'm hoping you do share, as you've obviously done a lot of work to get this far.  And sharing it into master would make it easier for you to keep moving forward, without having to constantly worry about porting your changes to each new release.  Also, there's a lot of people looking at doing this.  More minds looking at the problems will lead to a better solution.  That is why Ardupilot is where it is now.  

I do have to take exception with the comments about swashplates reliability. They are very reliable.  I've never had one fail in flight. Cost, yes, more expensive than a plastic fixed pitch prop. Complexity, yes a bit.  Really not that bad though.

I do think that if it you can make it work, fixed pitch props make sense, particularly on small machines where it can be hard to squeeze 2 swashplate systems in. But on larger machines, swash plates still bear consideration.

Comment by R. D. Starwalt on November 26, 2014 at 2:54pm

Bravo! Thank you for the write up and revelations.

There is a fellow over at RC Groups working on an scale Osprey would could benefit from your work.

-=Doug

Comment by Tipu on November 26, 2014 at 5:37pm

Great Work.

Keep it up guys

Comment by Team Tiltrotor on November 26, 2014 at 5:49pm

@Giovanni- Thanks! It was certainly not easy.

@Doug- We'd really love to have RPM feedback. We did do some research into it, but eventually we overcame some of the thrust problems with better flight control software. 

@Tridge- Thanks! We'd sure love to see VTOL in the software menu someday!

@ Rob- Hover pitch certainly is the weakest link in our design. We have some ideas we'd like to incorporate in our design to improve things. The nature of our testing did require pretty low winds in general so we did not push hover pitch very hard, but by operating smartly, taking off into the winds and landing into the winds without gross maneuvering we felt pretty comfortable. Neither one of us has any RC heli experience, and the swashplate was quite intimidating both mechanically and with the number of channels on APM 2.5. I'm sure swashplate on each rotor would make this a truly awesome flying machine, so we will not give up on the idea! We don't have any plans or desires to manufacture and sell tiltrotors to people. We (kind of) understand the code rules about releasing branches of the code.

Is it generally the case that the developers here do not get or expect anything in return for their countless hours and personal financial expenses? It is very admirable if that is true. I really wish / hope the people that gave us the power to create our own tiltrotor were compensated for it in some way! You guys have opened many doors for others to be successful. Such a interesting new way to invent.

@R.D. Ill take a look at the scale Osprey. If you could post a link that would be awesome.

Comment by Jiro Hattori on November 26, 2014 at 5:58pm

Great video!

Are you looking into this thread ?

https://groups.google.com/forum/#!topic/drones-discuss/HC0b1L5MIuE

Comment by Team Tiltrotor on November 26, 2014 at 6:11pm

Thanks Jiro- We were unaware of this link. That is an awesome looking RC tiltrotor. 

Comment by Rob_Lefebvre on November 26, 2014 at 7:22pm

It is sort of outside the scope of this blog post to discuss pay for coding, but it is definitely possible.

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