Vbar governor RPM unstable

Hello,

Last week i switched from futaba T14SG to Vbar Control Touch. I converted the neo express on my logo 550sx to vlink. All controls working fine, no problem there.
Last weekend on first testflight, after spool-up i noticed the headspeed drops when increasing collective. When decreasing back the collective (low stick) the motor overruns (1600RPM requested in VBar -> reaches at this point 2000RPM and then slowly goes down again).

My setup:
Motor Scorpion HKIII 4025-1100Kv
ESC: brandnew Scorpion Tribunus 120a 6s
Vbar Control Touch with neo vlink

I have governor set to Vbar Governor in VBC. Wiring of the neo: Master ESC to ESC on NEO, slave to RPM and from PC port ESC to TELE on NEO (telemetry). polarity is ok as i have the scorpion icon on my VBC and i have all telemetry data on the VBC screen.

As i'm new to Vbar Control Touch i probably missed something in setting up the ESC (all stock values in governor settings (just inserted the headspeed for each bank -> bank 1 1600RPM and bank 2/3 1800RPM), but i can't find the error :-(. I'm only since 1 year in the hobby so still learning on PID's etc..
All was working fine with futaba tx (flew it with the same Neo without vlink of course).

Can someone help me out, please? My logo800 is also in the queue for upgrade to VBC so really hope i can get things right in tx and enjoy again this exciting hobby.

Many thanks in advance for your help!

Hi,

can you please check if there are any tell tale log file entries?
Also, your current setup file would be helpful (save, download from cloud, zip and attach here)?

Two things come to my mind, either no valid RPM signal (governor runs on the underlying throttle curve), or ESC not in VBar Governor Mode (hardly possible with VBar Control Touch, if you don't mess with the settings manually, but check anyway which mode the ESC is in).

Kind regards

Eddi

Born to fly ...
forced to work.

Hello Eddi,

I've added a zip file with 2 log files in it:
1/ One with first flight on June 13
2/ Latest flight on yesterday: here you will see i changed the Vbar governor to PID with recalc values around 19:55:30 (low RPM warning) and then swithced it back to VBar governor.

And a second zip file with the setup.

What do you mean with "tell tale log file entries" and point out where i can find it, please?

When spooling up: in the status menu in VBC all the way down i see the programmed RPM and also the current RPM running up. So i see both. Wouldn't that mean the RPM signal is ok?
On the main screen, when i click 2sec on Scorpion icon i see "VBAR governor".



Edited 6 time(s). Last edit at 07/16/2020 11:03AM by ROMULUS.

Hi,

looks all good to me _but_

15.07.2020 19:47:15 Good;Scorpion ESC detected 
* 15.07.2020 19:47:16 Warn;Scorpion Input Signal
15.07.2020 19:47:17 Good;/battery/bt_1

where I can not tell what it means. I'd guess it means the ESC does not/did not yet see a motor off state to initialize, e.g. if you have the motor switch on a spring-loaded switch, and it's in Idle by default, after power-on.

With tell tales I mean log file entries about the RPM sensor (like input signal missing), which could mean the governor is indeed running on the fallback pitch curve.

You could try disconnecting telemetry so it's only running off the ESC and RPM wire (no data input besides that), and, for comparison, try the Scorpion Governor Mode/External Governor Mode, to see if the ESC works in general. I guess it does, if it was working with Futaba before.
Say, were you using the VBar Governor before, with Futaba, or was it external governor then?

Kind regards

Eddi

Born to fly ...
forced to work.

Hello Eddi,

With the futaba I used a Kontronik 100a ESC and programmed it in the neo as external governor. The tribunus is new as i did not have telemetry in the VBC from the Kontronik.
I will try what you suggested: run it without telemetry cable and do a test also with external governor (I did this yesterday but Heli only spooled up to around 900RPM which was strange as well).

Many thanks already for the ideas

Br



Edited 2 time(s). Last edit at 07/16/2020 11:57AM by ROMULUS.

Hello Eddi,

I just made some tests:
1/ with VBar governor enabled and telemetry cable (to tele1 port on neo) removed => no change, RPM remains unstable
2/ with external governor i only reach around 930RPM but seems to be more steady when increasing collective but of course difficult to test given low RPM speed..
Via the scorpion app i do not access to RPM settings (in ext governor mode). How can i adjust RPM in VBC while in external governor mode?

Any other ideas what might be wrong?



Edited 1 time(s). Last edit at 07/16/2020 12:20PM by ROMULUS.

Quote:

* 15.07.2020 19:47:16 Warn;Scorpion Input Signal

This is quiet a bug in the Errorbyte sent to us from Scorpion when it comes up while powering upthe ESC / Heli. It has nothing to do with your issues.

regards (EN) / Gruss (DE)

Rainer Vetter

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Hello Rainer,
Ok, thank you for the info.

Any idea what could be causing my problem?

Best regards,

Hi again,

I'd lean on the ESC, as a cause. Do you happen to have any suitable ESC with which you could do a cross check?
With Kontronik, only in the Kontronik Governor mode, they do not work properly with ours (rpm fluctuates).

Kind regards

Eddi

Born to fly ...
forced to work.

Hello Eddi,

I have some interesting news..

Today i converted my logo 800 also to neo vlink to work with VBC. On the logo 800 i have also a scorpion ESC but here a Tribunus 130a 12s which i flew with the futaba T14SG without any issue (external governor).

I tested vbar governor with VBC on the logo800 and guess what.. i have exactly the same problem on my L800-> headspeed decreases around midstick collective. So i think we can exclude already a faulty tribunus on the 550 as you asked me to test. Good, we are making progress..

A few questions:
1/ Besides pole pairs, BEC voltage and gear ratio, is it needed to change the default values in the radio to get the tribunus working well together with the neo (vbar gov)? It seems stock values do not work as it should. I'm a novice in this hobby, so i might be wrong in my reasoning.
2/ The good news, when selecting external governor everything is working fine, no performance decrease when touching collective, all smooth just as should be. But why it is not working with Vbar governor??

Something seems wrong in VBC in terms of settings of the VBAR governor.

Can you have another look at it, please? The neo follows obviously the V shape throttle curve which is programmed for vgov but headspeed should remain stable, no?

Kind regards,
Bart



Edited 6 time(s). Last edit at 07/17/2020 08:00AM by ROMULUS.

Hi Bart,

weird.

1/ no. Tribunus is supposed to be fully integrated, plug, select VBar Governor, set pole pairs and gear ratio, play.

2/ I wish I knew.

The underlying V-curve should act from center stick (0° collective), increasing throttle with positive and negative collective, to proactively add throttle for the torque to come. The governor then 'only' works around it.

And that seems what you seem to be noticing, on the 800,

Quote:

ROMULUS
i have exactly the same problem on my L800-> headspeed decreases around midstick collective

(not the same problem ..?) since this would be right, and different from what you posted originally?

Quote:

ROMULUS
Last weekend on first testflight, after spool-up i noticed the headspeed drops when increasing collective. When decreasing back the collective (low stick) the motor overruns (1600RPM requested in VBar -> reaches at this point 2000RPM and then slowly goes down again).

Kind regards

Eddi

Born to fly ...
forced to work.

Hello Eddi,

The problem I described for my logo 550 is completely the same as on logo800.
Sorry if that was not clear for you.

Motors spools up with collective stick at zero (all the way down), everything seems ok then.
When increasing collective towards midstick, the headspeed decreases (because of v shape throttle curve in neo I understand) and RPM increases again passing midstick to full stick.

I still don’t understand why the RPM does not remain stable throughout the complete collective stick range.
I programmed a pitch curve of -3.5degr at low stick and +8degr at full collective stick. I guess nothing to do with my RPM problem.

Somebody on FB advised me to change PID values to get things right. P=100 I=40 and D=7. He found this on the vstabi forum but I haven’t find it back on the forum. Would this be a solution?

What are the downsides using external governor instead of vgov?



Edited 2 time(s). Last edit at 07/17/2020 10:19AM by ROMULUS.

Hello Bart,

I thing we have to get our vocabulary straight

(Collective) Stick at zero, in my book, is zero 0° collective, not stick all the way down (–100 % actually).

Plus, I would never spool up a heli with significant negative collective pitch, putting considerable load on the power system, chassis, landing gear while on the ground, and risking that the control loop (worst case) violently asserts it's will, causing the model to sway or tip over.

I spool up at zero (collective), the precession will make it next to impossible that a model tips over (what pilots fear, that 'the wind' will cause the model to tip over).

As being said above, the VBar Governor relies on an underlying throttle curve. Means, if that curve was set up properly, you would hardly need the governor (like old school throttle curves). The VBar Governor then smoothes things out, and takes care of the inherent voltage drop (4.2 V/cell full ... 3.5 or less V/cell empty, would result in a 15-20 % rpm drop during a battery cycle).
This is why you notice the rpm changes with collective changes (at least on the ground, without blades), the proactive rpm control is static.

In flight, you should not notice it, to the contrary, it helps.

If you do, please do the following: do decisive climb outs, from a hover, and see if the rpm increases or drops. Adjust collective add until the rpm remains as steady as you like, in that maneuver (some prefer a slight increase, makes the next move crisper).
Then, dial in 1/3 of that value for cyclic add (or do flips on the spot, and see again how rpm changes).

These values come out pretty low, with Tribunus ESCs, since they are pretty aggressive themselves. Other/earlier ESCs needed more in the way of a kick in the butt, to maintain rpm.

Changing PID would only affect the work around the underlying throttle curve, and even then, I don't find all these values in the Electric Governor Expert so I wonder if the somebody on somewhere knows what he does ... for example D is only available for the Nitro Governor, where it makes sense. A nitro needs are real kick in the butt

The proactive rpm control (underlying throttle curve) is what makes the VBar Governor special: it can apply throttle when you do stick inputs, because it knows, while any external governor can only react if it detects an rpm drop which has already begun.
Plus, we can detect certain maneuvers if we control rpm, and adapt/adjust the control loop accordingly (e.g. prevent the violent tail wag in the infamous overspeed maneuvers).

Try and compare—it always comes down to personal taste, and what you expect/want from it.

Kind regards

Eddi

Born to fly ...
forced to work.

Hello Eddi,

Yes yes yes!!!

Thank you, with those adjustment headspeed is rock solid.
The spool up at mid stick is something I will do from now on.
No one in the club ever told me to do it (always done at low stick) but your reasoning makes senses.

Spool up at midstick with coll ad and cyclic ad adjustment just did the job.

So happy it’s solved.
I can start enjoying this wonderful product at the fullest

Thank you, Eddi!
Have a nice weekend
Bart