@ZvikaF thanks for sanity checking that. I will take a look later and make the correction.
@ZvikaF Are you sure you aren’t looking at the previous document. That was an error I made in the original version of the first document for the ATNH-rc1 version. I checked my links and they point to the correct release and document.
Testers @JoshW, @ZvikaF, @Steve_Mitchell, @Murdoch
Although I put ATC_ACCEL_Y_MAX as 27000 in my instructions, I think we could multiply that by 4 for your initial testing. I don’t know where this original value came from but I think it was derived from multicopters who have a much lower yaw acceleration capability than tradheli’s. At a minimum I would suggest at least doubling it.
It won’t affect the rate P and rate D tuning. It will make a big difference in the angle P tuning
EDIT: I added the analysis guide to the release page.
@bnsgeyer You are right, I was looking in the old doc, now I recall I have seen this before, sorry. 
I will try ATC_ACCEL_Y_MAX = 108000. ( gets out of limits error on MP)
Great job on the analysis guide (Power Point) 
As for the autotune procedure: do you want us to clear the resulted saved parameters from the previous tuning step / Axe ?
No, let it save the tuning values and continue with the next step. And you can keep tuning values as you tune the other axes too. That is why I removed he statement from the tuning instructions. I think this will be able to provide a full tune. But it has to be done in steps for now.
OK. will do … a bit later than scheduled …
Had some mishap today, probably not connected to the autotune.
installed the new FW, checked hoovering on my confined garden, all seemed well, then decided to see how the heli handles on alt hold takeoff, had some jump up at the previous flights, checked again H_COL_MIN / MID / MAX and fine tuned them.
at the following takeoff had a nasty jump, succeeded evading the house roof but ended up hitting nearby tree shade, needs new main gear, blades, main shaft, LG… horns… nothing special
it is probably something wrong i did, can not find it.
stabilized mode is ok and controllable, checked altitude command and could not figure it out.
here is the link to the bin file
https://drive.google.com/file/d/1Odg4LMHhEI8Xvz8RQab3p5T4wM1PMXfZ/view?usp=sharing
@ZvikaF I am sorry to hear of your crash. hopefully you’ll be able to get back into the air soon.
I reviewed the log and it appears that this was a vibration issue that caused problems with vertical rate and altitude estimations. This was not an issue with the Autotune firmware. I have flown this firmware multiple times and on every flight have used althold. I have had no issues with takeoff, hover or landing in althold.
You can see where the two z accel traces from the two IMUs have a bias between them and then the EKF error. After that the altitude grows as you begin your takeoff which lift off isn’t until when the desired and actual altitude separate between time 17:13 and 17:14.
In this plot you can see the vertical vibrations are shown to increase quite dramatically at the same time you get the EKF error. I think above 40 for the vibe signal is considered unacceptable for EKF.
So I am not sure what caused the IMU z accel measurements to diverge. Again sorry to hear about the crash and hope you can get back in the air soon.
@Leonardthall could you look at this and make sure I am not missing something with the position controller. I know that you had made some changes to it in 4.1.
Regards,
Bill
Thanks a lot Bill @bnsgeyer
Almost back to air, found more problematic parts (crooked tail rotor axle, bad tail servo…) it’s a part of the hobby.
As I noted before, I did not think it was autotune firmware related, but could not find the crash reason.
Out of the 3 450 helis I have, this one was making trouble from the beginning. (bought it second hand in bad shape).
I thought that I’m repeating an error and wanted another opinion.
Might be, that the tail rotor axle was crooked from the beginning and i have not noticed that.
Sorry to see you crash mate, I am glad you were not hurt. I think Bill is correct in his assessment. It is a good idea to keep an eye on your VIBE outputs on mission planner before testing Alt Hold for the first time, or have a look at the dataflash log to make sure everything is going well.
Both EKF are getting completly different values for height and the baro is also suffering from the ground effect.
Very large amounts of noise:
Thanks mate, another important point to check in the future, i usually checked it once at the beginning.
is it a good practice to takeoff on Alt Hold mode ?
@bnsgeyer is the man to ask what best practice is for Heli, but I my attitude with any aircraft is to treat it like it is trying to destroy itself or me until I have tested and validated each part of the tune and dependent modes.
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Just a quick update @bnsgeyer , finished all balancing and tuning, still getting high VIBE in hoovering.
Looked for the difference between the two helis that work fine and this troubled one, found that this is the only one without shock absorbers installation under the Pixhawk, need to install one
Hello Bill @bnsgeyer, Finished the new pixhawk shock absorber installation, and all the necessary alignments and tuning.
A big difference
had some tail wagging, had to decrease yaw P and D rates gain, still can see some fluctuations on the PIDY target versus actual. but ot seen on the heli tail movement.
Is there anything to do to eliminate it ? can i proceed to auto tune ?
Attached a .bin file of very low hover with some ground touches.
https://drive.google.com/file/d/1wMgFjBGzzoLivDGEc7K-FWsIt9umM5ru/view?usp=sharing
@ZvikaF Glad to hear that you were able to quickly get back into the air. Vibes look acceptable and the IMUs are tracking each other. How high are you flying? Your altitude is barely showing anything. Looking at the vertical accelerations, they are ok. Did you make sure your blades are tracking well? I believe I am seeing a 1/rev or 2/rev in there. By the way don’t forget to add fast attitude and PID to your LOG_BITMASK settings. The attitudes seem to be tracking well enough to start the autotune. Yaw looks good enough as well to start autotune. I’m surprised that your rate P gain is that low. Do you know the rate P gain value where it starts to oscillate?
Do another flight to look at althold and be sure it isn’t having issues again before doing the autotune. When you do start conducting autotune testing, Please be sure that you are flying in an area that is at least 50m by 50m. In the Max Gain, Rate P and Rate D testing, it will wonder a bit and you don’t have the ability to control it while it is testing like you do with the Angle P test. So if you make any inputs to the controls it will stop the test and give you control and start the test again once it sees the controls centered for 2 seconds. I would suggest starting with the yaw axis to see if it can tighten up the tune in that axis.
@bnsgeyer Thanks for the quick response, as i have some stock of spare parts for my fleet of 450, it was only a matter of dis / assembly time. this one needs a mast of 108 mm and I had only 111, so i had to extend too much the horns, and apparently, the new must is also slightly crooked, this might gives the 1-2/rev you see. tracking is fine, ordered the 108mm mast that will be changed on arrival.
Dew to a gusty day and tight area, hovering was at about 20-50 cm above ground, the high Z acc. readout seen, happened when slashed to the ground.
Having RPM telemetry on my radio (the newest Yappu LUA) helped a lot, the ESC seems to respond differently for every flight. this may explain the powered decent that had me soft crash the heli, during the last auto tune session a few months ago,.
Took the yaw P + D rates down to stop tail hunting, will check razing P influence.
Had fast attitude and PID bits on (65533) will add IMU_FAST as well, do you need IMU_RAW ?
changed the LOG_BITMASK to 425981 (skipped camera).
My autotune flights are done in a remote open area of few hundred meters, but the local pre checks is done in house at a tight place…
Thanks again for your effort and knowledge sharing, hope to bring some helpfull data on the auto tune.
Thanks to you all for testing.
Interesting. I guess I didn’t remember seeing the PID message. No I don’t need Raw IMU. I will look again. For some reason the data looked like it was at a lower sample rate. As long as you have the default bits as well as fast attitude and PID, then I am happy.
Thanks!
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Hello Bill, @bnsgeyer
I tried the Autotune RC2 today with a 380 size heli and wasn’t too successful, only managed to do the VFF tune on pitch.
Used 4 batteries (14mins each) trying to do the “Max gain, Rate D and Rate P” part of the tune on pitch and found the 23 second sweep is just too long for small heli’s. Is there any way to break this up? Without some kind of control inputs or position hold/return in the 23 seconds window, our small heli’s just drift to fast or have gone to far see. Lol
@Steve_Mitchell Hi Steve. Glad you had a chance to try it. Yes I think the VFF tuning is difficult for the smaller heli’s. They don’t tend to reach a steady state rate and that causes issues for the tuning. You should know what a good value is for your heli. I would continue with the max gain, rate p and rate d tuning. If you need help determining the VFF then send me a log of it doing that test and I will give you what I think should be the right number. Post the logs in any case so I can see what it is doing.
As for the max gain, rate p and rate d tuning, I realized that it was pretty long and added velocity feedback but that must not be helping. One other reason that could be happening is due to the swash servos not being trimmed so that there is no I term being used when holding a hover on a calm day. But I still think the trim should have helped and kept it close to level.
Please post you logs so I can have a look. Thanks for testing.
Try the yaw axis. Maybe it will hold stationary long enough to get through the sweep.
@bnsgeyer Okay, I’ll give it another go in a bigger area (200x200m). Also, will try the yaw axis first.
This is the VFF tune flight. I had no problems here. Was fast and easy to do.
https://drive.google.com/file/d/170IqFLDcIMlyhkxvtq4DAXd-uC76osr4/view?usp=sharing
This is one of many flights trying to get just the (2) max gain, rate p and rate d tune done and falling. It just drifts off too fast.
https://drive.google.com/file/d/1aco6PR519u3c-XRB08XPG77_J300wPta/view?usp=sharing
Heli specs:
Heli Size, 380
Number of main rotor blades, 2
Main Rotor Diameter in meters, 0.843m
Tail Rotor Diameter, 0.195m
Takeoff Weight,1.900kg
Rotor Speed (RPM) =2220