Trex 600 stretched (700) Pixhawk 3DR tuning

Got it! I set all that to what you recommended…

I had 3 different flights each one with different blades and P&D Roll setup one time P,0 and D,0 and, one time half value

so tried pretty much everything possible ;(

the last thing I am thinking of is that the new ESP shaft not precision tight, and since its long shaft and the bearing inside the block not tight with the shaft, if you shake the shaft there is about 0.001 play
so maybe this setup for the old 600 ESP not quiet good! and have vibrations issue even if its brand new!

the reason I say that because I replaced everything new.
and I removed the head and spin the shaft and when I touch it with my finger was a vibrating, in my little machining experience its about 0.001 to 0.002 runout

you know that runout in the shaft will increase the runout in the rotor disc and make it worse !

I am going to use my V block tomorrow and check the exact runout in that shaft

oh by the way I checked the blades and they are exact 0 and balanced with equal CG

I can machine my own shaft !! that way I can make sure it will snag fit the bearings!

so much hassles !!

anyway; the good news is that I received the new PIXHAWK 2 with here 2 today from IRLOCK

I am going to install it in my custom made Heli! ! :wink:

if that will work, I will throw this one away and buy another new one and put it in this heli !!
at lease its good 3 IMU so no troubles regards vibrations!

I appreciate your help Bill

Ozzy

parameters AUG-23-2019.param (14.1 KB)

Yes it has 3 IMUs but only 2 are isolated from vibrations. Even then that doesn’t guarantee that you won’t see elevated vibrations. Don’t get me wrong, it does help but there are a lot of things that go into vibration management. And that is only the high frequency stuff.

The low frequency oscillations are inherent to the stability of the vehicle (design). So the vibration isolated IMUs will not help with this issue.

so you think we can’t tune the Althold or poshold before we solve the Roll axis vibration right ?

I am trying everything possible to get it right !

The weird thing is that the heli fly really smooth and I don’t see any visible vibration

So setting up the INS_ and the frequency didn’t help?

Thank you
Ozzy

Yes I think we can move on. I’m not sure how you are maintaining configuration control of your parameters. I am very confused at the moment.
I’m not sure why you were messing with the Roll P and D parameters for the roll vibration issue. I thought I said that P and D gains don’t help with vibrations issues.

Yes I think the INS_NOTCH is helping with the vibrations in the roll axis. Please set the INS_NOTCH_FREQ to 21. The rotor speed you gave me is not matching what the FFT results. The FFT is indicating that your rotor speed is closer to 1200 RPM or 20 hz. So I’m gonna split the difference.

Now here are the values I want you to set for pitch and roll parameters. Please just fly this. I think we are close
ATC_RAT_PIT_D,0.001
ATC_RAT_PIT_FILT,10
ATC_RAT_PIT_I,0.12
ATC_RAT_PIT_ILMI,0.08
ATC_RAT_PIT_IMAX,0.44
ATC_RAT_PIT_P,0.01
ATC_RAT_PIT_VFF,0.18
ATC_RAT_RLL_D,0.001
ATC_RAT_RLL_FILT,13
ATC_RAT_RLL_I,0.12
ATC_RAT_RLL_ILMI,0.08
ATC_RAT_RLL_IMAX,0.44
ATC_RAT_RLL_P,0.02
ATC_RAT_RLL_VFF,0.18

If this looks good for the pitch oscillations, then I think we can move on.

Perfect I will go ahead and copy these parameters

Regards the P and D for the roll axis ; sorry for any confusing I caused , I was messing with them lowering them to 0 thinking that the VIB at the roll will be gone .

I will copy your values and report back With new flying log

Thanks a lot for fallowing up with me!
Ozzy

Be aware that the Pixhawk 2.1 is sensitive to wrong mounting!
In March I changed my FC to save some weight and it worked.
Read this: Flybar 450 Heli in loiter mode

Fred_GOEDDERT
Thanks a lot for the link thats a rich information everybody need it, I am going to write all the notices down to make sure I Am going in the right road! If any symptoms appear !

As of the location; that is why I like big ships just to give me different options to mount the FC but on the 450 size kinda hard to find more spots.

After placed the shaft on a Magnetic V block
It was 0.0001 very nice !

Next step is making third bearing block…

Step after : flatten the main gear and the autorotation gear using AAA surface plate

The final step will be tighten the bearing blocks the way can pull each bearing from other side to make sure the shaft set snag !! No play

Thank you
Ozzy

Hi,
I had to scrape the Hub to get tight runout, but the main gear turn to be in a good shape, but since its plastic will give and take and unfortunately will wobble!!! there is no way to stop that wobble!

I also tightened the both bearing block to pull the shaft into each side, but I didn’t put the third bearing block since its not here yet! but now the shaft is solid no movement, it was night mare to get these couple things right!

now I lowered the P gain from 0.015 to 0.01
and got the result bellow! I don’t think this heli will give better result in Freq oscillation! just tried every possible thing, and came up with few things from my own! like putting washers between the frame one side only to each bearing block, also add home made washer under the bearing block to clear the main gear from touching the frame things like that!

I didn’t change the Freq to 20 because I replaced the Main gear and now its 110T instead of 112T so that will give me more RPM, I also ordered 16T pinion instead of the current one 14T
that way I can get nice 1500 RPM and control the RPM from the setpoint!?

Please can you tell me if I am ready for the next step after hover trim and my heli now fly nice and almost hand free!

Thank you
Ozzy

parameters after scraping the Hub Aug-29-2019.param (14.1 KB)

Hi Ozzy,
I looked through the parameter file that you supplied and it’s not exactly what I requested you to fly. Is that what you flew in the log files?
Please fly configuration I requested. Thanks!

By the way, it is not the frequency of the notch that I’m am concerned about. It is that you used different settings for ATC params than what I requested.

Oh so sorry that was big mistake! I loaded the old parameters instead of the new values !!

Will fly it again today with the new parameters and values you posted here !

I appreciate that

Edit; here is the new logs for the new flight
Thank you so much!

new parameters AUG-29-2019 925AM.param (14.1 KB)

Ozzy,
I did a little experiment tonight with my helicopter. I did two flights, one with blade bolts lightly tightened and the other with the blade bolts very tight. With the blade bolts very tight, you can definitely see the difference in the aircraft vibration from the data. This is the roll axis for the loose blade bolts

This is the roll axis with tight blade bolts

The big thing to note is the higher frequency noise in the roll rate signal. You also can see more oscillations in the data which is about 3.5 to 4 hz.

Looking at the pitch axis, you don’t see as much noise in the data between the two but you do notice the 3.5 to 4 hz oscillations becoming more pronounced. I would have never guessed that the 2/rev vibration would have affected the lower frequency oscillations.
Pitch axis with loose blade bolts

Pitch axis with tight blade bolts

So Ozzy, are you making your blade mounting bolts really tight or are they being restrained some way from being able to swing forward and backward? So I don’t have a good way to tell how tight to make those bolts. I would say that they should be tight enough to keep the blades from swinging back during a slow rotor startup. If they are so tight that if you were to tip the heli on its side with the rotors parallel to the ground and they don’t swing down, then that is probably too tight.

Hi Ozzy, with regards to this comment. Can you confirm that you are using a throttle governor on your speed controller and not just setting a single pwm value without a governor?

Hi Bill, thanks a lot for posting pics showing the different between the two flights!!

I can see now the freq-oscillating! Even when you tight the blades still your Rate better than mine!!

I tried all methods regard the blades

I have had tightened them, and loosen the blades and based on the size of the blades 710mm I had to make it in between tight and loose, and I use the old method by hold the hole and shake it little bit to see if the blades move …

But I am thinking maybe the front TT gear mash is not loss and can cause that!

But can you check your heli and see if you have wobbling main gear and autorotation gear ?

I have normal amount of gear wobbling and you can’t fix that, but if you have main gear wobbling that will tell me it’s not that who causing the vibration !

I run it today on the bench with head and complete tail removed
Instill see some freq oscillating!

I am Changing the cyclic servos to BK 8001

And just to make sure it’s not servos causing that!

Mate ; you brought nice point here
I have had calibrated my HW 130 opto and got it set then I assign ch 8 for throttle, basically hit the switch and the speed go to what ever max is

Now I just replaced my main gear to 110 t and changed my pinion from 14 to 16t

That will increase the head speed to ~1500

440kv 10 pole
6s 60c 5000 mah
110 main gear
14 pinion
130 A hw v4 opto esc

Thank you guys for the help !
Ozzy

Ozzy,
Based on your last flight. Pitch is not following as well as I want it too.
Halve your P and D gains on your Pitch axis only. Then raise the ATC_ANG_P to 6 in 0.5 increments. Post a log with the ATC_ANG_P at 6. If it feels good in pitch with ATC_ANG_P at 6 then try loiter for 30 seconds and see if it holds position without toilet bowling (wandering about).

What do you mean you don’t like my pitch ?? Is that the freq oscillations? Or not tracing the des pitch ?

I will halve he values and try the loiter mode

I am working on smoothing the mash gears between the red gear umbrella and the front red gear

Hope I can lower the vibration! Otherwise there is no way I can get it lower than I less if I machine metal main gear !!!

That will be to much !!

I will report back with logs

I appreciate your help
Ozzy

It’s not tracing the desired pitch very well. I also noticed the oscillations. So I am having you halve the P and D gain to help reduce the oscillations. And I am having increase the ATC_ANG_P. That should read ATC_ANG_PIT_P in the previous post. Having you increase that to help reduce the error and have the actual pitch attitude trace the desired better.

Make sure you get me some data in stabilize before going to loiter with the new ATC_ANG_PIT_P.

Hi Bill,

I was able to get the ATC_ANG_PIT_P,5.5 with no problems and I tried the loiter mode… its solid in the sky, but the collective is weird!

I will try the 6 today

when I switch to Loiter and I am already about ~1+ collective pitch the Heli want to sink down and land so I had to give more + collective to keep it up to the point that I need to lower just a hair then the heli stay there then if I switch to Stab it will go up and I had to lower the collective !

like you see in the logs, it land itself couple times because I was about +1 collective or so…

but there is no toilet bowling at all.
here is the logs and the bin I flew it on STAB mode then switched to loiter mode.

I appreciate your time helping me!
Ozzy

loiter test mode.param (14.1 KB)

Ozzy,
your problem can be fixed with the param. IM_STAB_COL_2 and _3.
Chris Olson is explaining that in his video ArduPilot Trad Heli setup video2.
You can forward at about 16 minutes than that subject starts. At about 20 minutes he is talking exactly about your experience you have at the moment if you do not adjust those param.s to the right values.
Good luck.
http://ardupilot.org/copter/docs/traditional-helicopter-configuration.html

1 Like

I did copy the video and did exact thing what Chris recommend
But my mid stick is 3.3+ not 0.00

My stab_col 2, 550
Stab_col 3, 650
Now my max is 11+
And my min is 2.6 -
The 0.00 collective will be on the first 1/4 stick

And that what make me thinking and asking why he want the mid stick to be at 5.5+ and not 0.00 so that be easy for me to leave my stick to mid center when I want to switch between any mode !??

Now I change STAB_COL 2, 575 and STAB_COL 3, to 625

And when I was hovering on Stab over 1/4 stick then switched to loiter mode the heli smashed into the ground !!

So why you don’t have 0.00 on mid stick( center stick) not on 1/4 stick thats for STAB mode
Also on passthrough mode …

So that he heli will return back to level wen I have my stick on center mid 0.00 !!

Again my setup is;
Pass through mode max : 11+ Mid; 0 min:0

Stab mode max : 11+,
mid stick ( center stick) : 3.3+
And the 0.00 on 1/4 stick
And the 2.6- on bottom (lower stick)

Please correct me if I am wrong

Here is pic of my 0.00 collective

https://uc24d7df7be1734cf64336e58ee1.dl.dropboxusercontent.com/cd/0/get/An230PbnGrukaCRi0D52g7AnJER69QemRSd4XZDFYdnh8q1JxH6wlUmOKtwhHZMoI4yi7jARnDJlNS7P_dUPGcZlcy1VVKP2Bag3fya0SItD6GlzxACNoSbawiXhdxdsPII/file?dl=1#

Thank you
Ozzy