Yeah,that’s a major issue with the direct drive. I get it from a mechanical simplificity point of view, but you then add one more motor/esc that can also fail, so I’m not quire sure what the benefit is.
Yes, I have on both Helis DDVP with an electric motor.
TR700 ( Jet-ranger ) and TR600 with longer tail. It is so easy to fiddle around this way. The main motor uses all its power for the main rotor only. As Jakob is saying for mechanical simplicity.
If I am building a new Heli and the Autonomous Auto-rotation is working ( available) for that reason, I would use a torque tube or belt driven tail for sure. But I cannot change the others back because their tail booms are not standard anymore. No tail failure for several years now.
That’s a really good looking Jet Ranger Fred.
In principle, a DDVP heli can be autorotated as well. I suppose it does depend on how it’s wired. Either the tail motor and esc is still functional in which case yaw control is still available. Or, the tail motor/esc is out, in which case it is just like a mechanical tail rotor failure case when the tail is driven off of the main shaft (a failure case that I will be developing for in the code).
For direct drive tails I would need to add in some extra functionality to the code to prevent the tail rotor esc from being shut down in the ‘practice autonomous autorotation’ whereby the pilot initiates. I don’t have the capacity to add this in at this point in time as I am still getting the fundamentals sorted. But, that’s not to say its not something I could look into later down the line.
Matt thank you for the reply. I will watch your development with interest!
I have some exciting news to share!
As some of you will already be aware, I submitted a funding request for a larger airframe to support the autorotation development. Well, this funding request was accepted by the ArduPilot funding committee! As an added bonus, @cczeets of Terraplane (an ArduPilot partner) has also contributed to the cause to enable me to get a larger 700 size heli for testing. So a huge thank you to both parties for the support that you have shown me in this project!
Call for Test Data
I am currently working on the flare phase. I am trying to define a target trajectory that the heli will attempt to follow during the flare. I would like some test data from autorotations from various helicopter sizes. If anybody has any log files where they have performed autorotations (or would be willing to go out and record some), I would be very appreciative if you could share them with me. The main things I need are the positions and velocities which come in any log file. An added bonus would be if you have an RPM sensor fitted so that I can look at the head speed as well. Any data would be most appreciated!
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Setting LOG_BITMASK to 65535 (Default) will give me all the data I need.
I have spent some time now grappling with the flare-phase controller. It has taken me a while to get my head around it but I am now making some steady progress. The video below shows the progress so far.
What can be seen:
- AP is monitoring its current state and looking forward to determine if it can safely complete a flare. It does this by balancing altitude, decent velocity, and acceleration requirements.
- When AP believes it can complete the flare it does so. Adjusting its trajectory to again balance the exit requirments placed upon it (i.e. finish at this altitude, with this vertical speed, and don’t demand more deceleration than X).
At this point in time it is still very crude and I have a list as long as my arm of improvements to be made (e.g. add in forward speed and head speed requirements to be balanced, improve decision making using statistical distributions to award ‘confidence’.)
But, I wanted to share this, as im not going to lie, I am pretty excited about it 
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Hi Bart,
Thanks for your interest in the project, my apologies for not doing an update in a while. In short I am at the phase whereby I need to do more testing in real life and I am currently tuning a larger heli that will require a less ‘aggressive’ autorotation. If your interested here is the maiden flight of that aircraft:
Also, in case you haven’t seen it and are interested, I gave a presentation at this years ArduPilot unconference whereby I gave an overview of what the current state of the controller looks like:
I have also added support for autonomous autorotation bailout for external governors. This has already been merged into Master:
I needed this functionality for improved bailouts on my test vehicle setup. As part of that PR I also added support for governed DDVP tail rotors (and the accompanying bailout). I have modified my little 450 to have a DDVP tail rotor now:
The only trouble is I messed up when I was threading the rotor shaft, so at the moment it has horrendous vibrations that completely upset the EKF so I need to find some time to redo the shaft. Then I will have another configuration available for tests
Let me know if you have any specific questions.
Matt
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Thanx Matt, looking forward to your progression. Just for the fun, here’s a video of last week’s test of autoland that went smoothly. if only I got autorotate on it 
Autoland
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Hi Matt,
Any update on your autorotation project?
Is there anything I can do to help you progress/finalize this project?
Bart
Hello I have little 450 that’s perfectly tuned, and I want to test automatic autorotation
Can I test it on 4.1.1 stable firmware?
I see that there is the AROT params, can I test it under our own responsability?
@kuspower are you seeing the AROT param in the parameter list when connected to your flight controller or only in SITL? You should only see it in SITL. You would have to compile your own version and change the define to allow autorotation features to be available on your flight controller. However currently the only features available are the entry and glide phases of autorotation. It doesn’t have the ability to perform the flare and landing.
@bnsgeyer just flashed stable to a board. AROT params are not there, so it is still SITL only.
@kuspower as Bill says this is SITL only still. The reason being is that its not complete. The copter will literally glide itself into the ground as is. It is something I am still working on. Rest assured it has not been forgotten, I am still working on it, it is just something that I struggle to find the time to work on, hence it is slow progress.
Hello, I see it on sitl at this time.
And I tried it on sitl but there is no way to make it work….
I take off in guided mod, to 100 meters alt and i cut motor interlock to stop engine, i tryde to quickly activate autorot mod, but no way, rotor lost all its rpms….
In the final feature i hope that autorot engage automaticaly below set rpm?
And in sitl, how to make it work?
Envoyé de mon iPhone
There is no in built SITL functionality to enable autorotation. Simply put the physics for autorotation hasn’t been programmed.
All development has been done using real flight.
Hi Matt,
I was wondering if you have any spare time to continue progressing the autorotate code.
If you need an resource to help test it I have a 500 and a 760 helicopter currently flying on ardupilot that I would be happy to test with .
Hi Tom @TomBarwick
@Ferrosan has continued with this work and has submitted code for a PR that is currently in review. Here is a link to the blog that Ferruccio posted on his progress.
Automatic autorotation update
We have one hurdle to overcome which is a reliable high rate height above ground sensor. Currently Ferruccio is using a laser rangefinder where the sample rate was increased to 100hz. We are looking at developing a complementary filter that utilizes the rangefinder data at a lower sample rate with another vertical rate source.
The PR for the full autorotation capability is at this link
We will keep you posted and will take you up on your offer to test this PR.
Thanks,
Bill