ArduPilot now supports TiltWing VTOL aircraft! First test flights done earlier today in Canberra

We did the first test flights of the Unique Models CL84 TiltWing VTOL with ArduPilot today. Support for tilt-wing aircraft is in the 3.7.1 stable release, with enhancements to support the tilt mechanism of the CL84 added for the upcoming 3.8.0 release.

This CL84 model operates as a tricopter in VTOL flight, and as a normal aileron/elevator plane in forward flight. The unusual thing from the point of view of ArduPilot is that the tilt mechanism uses a retract style servo, which means it can be commanded to be fully up or fully down, but you can't ask it to hold any angle in between. That makes for some interesting challenges in the VTOL transition code.

For the 3.8.0 release there is a new parameter Q_TILT_TYPE that controls whether the tilt mechanism for tiltrotors and tiltwings is a continuous servo or a binary (retract style) servo. In either case the Q_TILT_RATE parameter sets the rate at which the servo changes angle (in degrees/second).

This aircraft has been previously tested in hover by Greg Covey (see http://discuss.ardupilot.org/t/tiltrotor-support-for-plane/8805) but has not previously been tested with automatic transitions.
Many thanks to Grant, Peter, James and Jack from CanberraUAV for their assistance with testing the CL84 today and the videos and photos!

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Comment by Ravi on January 26, 2017 at 6:40am

wow, the ultimate VTOl aircraft. this uses minimum motors and is the optimum way for a VTOL fixed wing. another aircraft is boeing OSPRAY which uses similar technology. very simple to built from scratch. only challenging part will be tilt mechanism. welcome AP2.8. I am sure one day AP will bring this surprise.

Comment by Tommy Larsen on January 26, 2017 at 8:02am

Nice work!

Does it mean that a one-engine Delta wing can take off from standing postition (like on the picture in this link: http://diydrones.com/profiles/blogs/miniracewing-fly-fast-stay-low)  and then do a transition to forward flight ??

A funny idea anyway :)

Comment by JB on January 26, 2017 at 8:38am

Sweet! Well done. 

I'd really be interested in the next step which would be to use separate servo's on the tilt wings for yaw control, so the rear prop could be fixed instead. Differential tilt on the wings could then could also become aileron control, or elevon on a wing type aircraft. That plus using larger wing prop/motors to produce most of the lift would probably shrink the components of a VTOL/QP to the absolute minimum (3 motors and two servos).

Comment by James on January 27, 2017 at 1:22am

@JB I have written a fork to do this on a custom airframe using the tilt servos for yaw.

It works very well in a hover, very hard to make the mechanism strong enough for forward flight while being fast enough for yaw.

Most tiltwings use geared servos with high ratio which does not allow use for yaw


Developer
Comment by Andrew Tridgell on January 27, 2017 at 4:29am

@Tommmy, not yet, but I am planning on adding tail-sitters soon.

@JB, it would be simpler to just make it behave like a dual-copter, using large elevons for pitch control in hover.


Developer
Comment by Andrew Tridgell on January 27, 2017 at 4:33am

@Ravi, I think supporting an Osprey type model in ArduPilot won't be hard now. Maybe you should buy one (there are several available) and we can work on it?


Moderator
Comment by Graham Dyer on January 27, 2017 at 5:59am

Tridge, are front-motor-yaw tricopter layouts supported? I know there was a PX4 version but not sure if that's the same thing here.

Comment by JB on January 27, 2017 at 7:47am

Hey James. Nice!

I'd be interested in trying it if I may. Can you link to the fork please?

I'm looking at a small custom airframe, sub 1kg, with a lift body, so I'm hoping for fairly small high aspect ratio wing area that should be easier to move fast enough for yaw. Like that it's mostly just the wingtips with rotors that rotate instead of the whole wing, which need not be as structural.

The idea is to use a very large, third, non-pivoting rotor as the main lift rotor (that stows in the fuselage when not in use, by braking the rotor at the right spot), meaning the two smaller rotors on the wings can have props/motors optimised for forward winged flight (read high cruise pitch props on small motors). That way it avoids the orientation problems that tail sitters suffer from, so wings can always point into the wind, even in hover. (ie the airframe maintains the same level attitude regardless if in hover/forward flight). 

Essentially a Osprey configuration with small props for attitude control in forward flight and hover, and one large fixed prop for hover, that shuts off in forward wing flight.

--

Tridge do you mean a dual motor tailsitter like this?

Comment by James on January 28, 2017 at 6:09am

@JB

Your idea is very interesting and sounds promising. Getting majority of lift with a non tilting motor would solve a lot of structural issues as the tilting mechanism can be weaker. I think your solution would be easy to code for.

My branch is here: https://github.com/JMare/ardupilot/commits/tiltyaw

Its designed for a +quad configuration with counterrotating tilting wing motors. I built it on tridge's tiltrotor code but i had to hack the tiltrotor stuff up a bit to make it work.

The code smells but it works in the sim and is promising in real life.

Comment by Tommy Larsen on January 28, 2017 at 6:22am

Would it be possible to use an original MTD(My Twin Dream) with engines placed as is. Put it uprised on it's tail somehow (with some kind of legs) and take of vertical and then do a transition to horizontal flight? The 2 engines are CW/CCW...

Almost like this one, but one engine on each wing

https://www.youtube.com/watch?v=5J6D8a3SIvg

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