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Old Sep 05, 2012, 01:20 AM
Head in the clouds
nascar1929's Avatar
United States, NC, Gastonia
Joined Jan 2012
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Quote:
Originally Posted by beenflying View Post
The ZYX holds the tail very well. I have personal experience with the DS115MG on the ZYX and it's excellent.

If all is well you should be able to have the gyro tail gain at 100% and the Tx HH gain at 32 in the ZYX monitor screen. Tail PID is 80 50 15 and Decel L/R = 50/60.

Servo arm length needs to be 7 to 8 mm.

Don't run too low a head speed. Aim for 2800 to 3200, using your pitch curve and keep the throttle curve nearly flat above 60%, or use idle up with a flat throttle curve, and switch to it just before lift off.

Also make sure your collective pitch to tail comp is set the right way around. Middle of the throttle stick to full pitch, the leading edge of the tail blades should move towards the boom. If you have zero set for this, try a value of 8 or -8 (after checking the direction).

As always, make sure you replace your tail blade holder bearings, if they are not new or you have crashed recently.

Eliminate any vibration, especially from the tail (blades, bent tail shaft etc.).
Took the main and tail blades off to run it up on the bench. There is a slight vibe from somewhere causing the tail servo to twitch.

I noticed the majority of the vibe was coming from the main motor area when I felt around the motor mount screws on the sides of the frame. The vibes would lessen as I felt further back. Is there a fix for this like rubber motor mounts or something?

I removed the entire tail rotor assembly and ran it up again to see if I could isolate other vibes. I could see that the tail drive shaft is out of round while it was spinning. Not a whole lot, but noticeable. I am thinking that this may be causing some vibration in the tail. I am going to order some new drive shafts and see if I can get one that is true round and not warped if possible.

Going over the main rotor head, I found that I could grip the main shaft and it would wiggle back and forth a hair. Not up and down, but front to back and side to side. I removed it and took the thinner main shaft washer off and replaced it with the thicker washer. No more movement after doing this. Hopefully this will help. Even though they are new, I may need to get new bearings and swap them out.

Once I get the tail drive shaft replaced, I will try you settings for the tail.

Not sure I understand the collective pitch to tail compensate. How do I do this?
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Old Sep 05, 2012, 01:36 AM
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United States, WA, Issaquah
Joined May 2011
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Originally Posted by sgbfly View Post
Hi,

It's not related to D-gain so far as I can tell. I've observed the sudden nose up with the D-gains at 10 and also 30.

I've also seen it happen with the I-gains at 80 and also 100. However, I have not had chance to do any methodical testing. That said if anyone has any good ideas I am willing to flash back to v3.5 and see what happens.

It's interesting that you say you seen reports of this sort of instability before with other fbl units.

S
What kind of blades are you running? Are they designed for FBL?

What I'm thinking is that helicopters have a natural tendency to go nose-up in FFF and FBL controllers are supposed to correct for this. FB blades makes this tendency worse when run in FBL configuration, whereas blades designed for FBL mitigate this tendency to some degree.

In any case, countering the nose-up tendency in FFF is a fast response kind of correction so increasing P-gain and I-gains both should help. In your video it did look like the gyro was catching up to the correction at some point so I think even 5 points of extra P and I might do it.
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Old Sep 05, 2012, 04:46 AM
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Nottinghamshire, UK
Joined Dec 2009
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Originally Posted by Dr.M View Post
What kind of blades are you running? Are they designed for FBL?

What I'm thinking is that helicopters have a natural tendency to go nose-up in FFF and FBL controllers are supposed to correct for this. FB blades makes this tendency worse when run in FBL configuration, whereas blades designed for FBL mitigate this tendency to some degree.

In any case, countering the nose-up tendency in FFF is a fast response kind of correction so increasing P-gain and I-gains both should help. In your video it did look like the gyro was catching up to the correction at some point so I think even 5 points of extra P and I might do it.
Good idea's!

No they are not fbl blades. They are standard HK CF blades

OK, lets spark a mini debate as you've made me do a little research into the difference between FB and FBL blades.

1) FBL are sometimes heavier
2) FBL blades have a COG more towards the tip
3) FBL blades are weighted more towards the leading edge so they lag a little when spun up
4) FBL are more carefully balanced

points 1) to 3) are to increase stability. 4) is for the benefit of the gyro by reducing vibs.

The HK blades are 21.7g each and the COG is 16.3cm from the centre of the bolt hole. I do have an alternative set of blades from LH. These LH blades weigh 24.7g each but the centre of gravity is only 15.0cm from the centre of the bolt hole. However, the LH blades do slightly lag the HK blades when hung from a screw driver. So 2 out of 3 stability-wise, worth trying...?

So, what I'll do today is flash back to zyx fw v3.5 and try a different set of blades and see what happens in FFF into the wind. I'll only get chance to make one change this lunchtime and this one seems the most obvious to me.

Good plan?

S
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Last edited by sgbfly; Sep 05, 2012 at 04:52 AM.
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Old Sep 05, 2012, 04:54 AM
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Nottinghamshire, UK
Joined Dec 2009
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Quote:
Originally Posted by Jimbo45cn View Post
Simon,
First off, thanks for your instructional videos and how to set up a flybarless head and this gyro. Without it I would have been totally lost.
As concerns the behaviour of the 3.5 version, it almost looks to me as if the gyro is trying to slow the heli down, maybe? dont' know why, but looks like it's just "putting on the brakes". Anyway, keep up the good work. Jim
Thanks Jim

As an aside, If I get chance I would like to build an index for those videos to make them more user friendly
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Old Sep 05, 2012, 05:03 AM
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Originally Posted by beenflying View Post
You're welcome. Yes, they appear to have forgotten to change the version number with that release, so we have just called it v2.5, since it came with the v2.5 PC app.


That's very interesting. Thanks for reporting back. I haven't seen it either, but I haven't been flying the ZYX's much since the v3.5 was released. I just did test flights at home, where I can't really get up a lot of pace.

I wonder if unochen has noticed this and can give some advise how to stop this happening.
Ah, that would make sense wrt to the version numbers. It's the kind of thing I would forget to do!

Yes any advice would be appreciated because I'd really like to get v3.5 working well for my flying style.

S
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Old Sep 05, 2012, 05:19 AM
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Australia, NSW, Ingleburn
Joined Dec 2009
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Quote:
Originally Posted by Dr.M View Post
What kind of blades are you running? Are they designed for FBL?

What I'm thinking is that helicopters have a natural tendency to go nose-up in FFF and FBL controllers are supposed to correct for this. FB blades makes this tendency worse when run in FBL configuration, whereas blades designed for FBL mitigate this tendency to some degree.

In any case, countering the nose-up tendency in FFF is a fast response kind of correction so increasing P-gain and I-gains both should help. In your video it did look like the gyro was catching up to the correction at some point so I think even 5 points of extra P and I might do it.
If it was simply a matter of blades wouldnt it do the same no matter what firmware you were running?
I might try increasing the P and I gains and see what happens.
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Old Sep 05, 2012, 05:26 AM
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Originally Posted by ingleburn View Post
If it was simply a matter of blades wouldnt it do the same no matter what firmware you were running?
I might try increasing the P and I gains and see what happens.
That would be good if you go down the gains route and we compare notes!

As for blades not necessarily, it could be that the new firmware is tuned towards a mechanically more stable heli.

S
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Old Sep 05, 2012, 06:58 AM
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Joined Dec 2009
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Latest news on the FFF into wind sudden nose-up problem with firmware v3.5.

The heavier blade experiment failed

HK-450GT FBL 090512 ZYX FW v3.5 Heavier Blade Experiment (3 min 38 sec)


These are the settings used:

[section1]
PitchAgility=35
PitchGain=45
RollAgility=35
RollGain=45
YawAgility=35
YawRight=35
YawGain=100
[section2]
FixMode=1
ServoType=2
SwashPlateType=2
ServoDirCH1=-1
ServoDirCH2=1
ServoDirCH3=1
ServoDirCH4=-1
ServoAdjustCH1=-15
ServoAdjustCH2=-5
ServoAdjustCH3=-4
AileronLimit=60
ElevatorLimit=60
TotalCoefficient=-60
PitchDir=-1
RollDir=1
YawDir=1
TailPoint=-30
TailLimitA=100
TailLimitB=100
OptimizationDir=-1
[section3]
Acc1=125
Acc2=55
Acc3=125
Acc4=125
Acc5=25
Acc6=25
DeadBand1=20
DeadBand2=4
DeadBand3=20
DeadBand4=4
PitchGainD=30
PitchGainI=100
PitchGainP=80
RollGainD=30
RollGainI=100
RollGainP=80
SpinSpeed1=35
SpinSpeed2=35
SpinSpeed3=35
SpinSpeed4=35
TailCompsate1=0
TailCompsate2=0
TailGainD=30
TailGainI=50
TailGainP=80
[FBL]
Preset=3
ModelName=HK-450GT FBL Tray Rev v3.5

S
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Last edited by sgbfly; Sep 05, 2012 at 10:42 AM. Reason: video & settings added
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Old Sep 05, 2012, 11:11 AM
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United States, WA, Issaquah
Joined May 2011
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Simon,

Good thoughts on the blades. Now that you've tried those settings with the new blades, I think it's worth tuning PID a bit. Try 90-105-10 on pitch/roll. Drop the main gains to 40.
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Old Sep 05, 2012, 03:10 PM
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How much cyclic pitch is applied at the limits you have set?
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Old Sep 05, 2012, 03:35 PM
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Originally Posted by Dr.M View Post
Simon,

Good thoughts on the blades. Now that you've tried those settings with the new blades, I think it's worth tuning PID a bit. Try 90-105-10 on pitch/roll. Drop the main gains to 40.
OK, charging lipo's now in preparation for giving this a go tomorrow

Quote:
Originally Posted by teamdavey View Post
How much cyclic pitch is applied at the limits you have set?
Pitch = +/- 10 Cyclic blade deflections = +/- 7

S
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Old Sep 05, 2012, 03:53 PM
as much as I can
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NZ
Joined Jan 2010
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Quote:
Originally Posted by sgbfly View Post
OK, charging lipo's now in preparation for giving this a go tomorrow



Pitch = +/- 10 Cyclic blade deflections = +/- 7

S
I'm wondering if 45 for the cyclic gain and 100 for the I gain is way too much I gain. I'd try reducing the I gain to 80 and the D gain to 10 or less, and see what happens then.

I would also recommend setting up for +/- 12 degrees of collective pitch and then reducing the collective pitch by using the pitch curve or pitch EPA's, if you want +/- 10 degrees. I think the gyro makes a lot of internal corrections based on this setting.
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Old Sep 05, 2012, 04:05 PM
as much as I can
beenflying's Avatar
NZ
Joined Jan 2010
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Just had another thought, Simon. I think you might be running into the limits at high speed, with a high collective pitch angle, so the gyro can no longer compensate for the pitch up effect. Try increasing your cyclic limits and collective pitch (as I mentioned above), even if you get binding in the corners. It shouldn't make the heli over sensitive, as in flight it's all done by the rate of change. I set my limits to just stop binding on the stick axis, or leave them at the default of 70.

Dr.M, I'm also wondering if this is the cause of pitch up during roll.
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Old Sep 05, 2012, 04:11 PM
Everyone is an idiot (or I am)
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United States, TX, Red Oak
Joined Jun 2012
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Quote:
Originally Posted by sgbfly View Post
OK, charging lipo's now in preparation for giving this a go tomorrow



Pitch = +/- 10 Cyclic blade deflections = +/- 7

S
Curious, are you at max pitch on these fff? If so, wonder if it would do it at almost full pitch?
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Old Sep 05, 2012, 04:55 PM
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ahamay's Avatar
Australia, QLD, Gold Coast
Joined Jun 2012
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Quote:
Originally Posted by Dr.M View Post
Simon,

Good thoughts on the blades. Now that you've tried those settings with the new blades, I think it's worth tuning PID a bit. Try 90-105-10 on pitch/roll. Drop the main gains to 40.
My Tarot 450 Pro has the Tarot FBL Carbon Fibre blades, and was fine with the previous firmware so I don't think it's blade related.

Another observation, you don't have to be going FFF. I've been flying (about half collective) along and a big gust of head wind has hit the heli and it's pitched back ele.
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