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HomeAircraftHelicopterFlybarless Rotor Head SystemsOther › Inverted D values. Please read
01-18-2009 10:19 PM  9 years agoPost 1
tchavei

rrProfessor

Portugal

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Hi.

This has brought to my attention through MrMels post on the vstabi forum and afterwards also confirmed through other posts on the german version of the vstabi forum.

It seems that if you use the arrows (up and down) on the D portion of the tail PID, you could be feeding in negative values without knowing. Basically what happens is that the arrows are inverted. When you press "up" you're really reducing the values and if you happen to be at "0" you don't realize it and start feeding in negative values.

After reading about this I've checked all my past and present configurations and I had that value wrong (inverted) in 7 of my 10 tail experiences. No wonder my tail was whipping when I increased the accel value. The system was calculating the error and then feeding back the negative value instead of the positive.

This might be just a minor nuisance to most people but for perfectionists like me, it always bugged me why I couldn't have the perfect tail like with my spartan. Well now at least I found the reason why D=0 worked better than D=25 lol.

To check if you have your D value correct (or negative) just open your file in the killer panel (also called Vbar overview). You will see the D value on the right side. If its positive, you're off the hook, if its negative... well you know what to do.

Regards
Tony


--------------------
"Perfection and patience usually walk side by side..."

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01-19-2009 12:24 AM  9 years agoPost 2
Heli 770

rrProfessor

USA.

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Tony
I think now I understand way you had that Thread where you were reversing this to reverse that so this isn't reversed. You gave a lot of guys headaches and drove some to drinking! Glad you found out.

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01-19-2009 02:01 AM  9 years agoPost 3
tchavei

rrProfessor

Portugal

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Well actually that was another bug altogether Well... not a bug as the software was doing what it should if the rudder was setup as it expected but not otherwise.

my vbar learning curve has been steep but atleast I'm getting to learn things really deep. I've setup 3 vbars at my field in less than 10 minutes and everyone is super happy with their performance. It has been my own bird that has experienced every wacked out problem you can think of.

Finally its performing really well. one tweak or two on the phasing and tail and its nearly perfect. Right now the tail performance is 95% of the spartan's and cyclic wise it surpases every flybar nitro heli I had the chance to fly.

Tony


--------------------
"Perfection and patience usually walk side by side..."

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01-19-2009 03:27 AM  9 years agoPost 4
MrMel

rrProfessor

Gotland

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yeah, it really flies bad with -25 in D-Gain

Reference: http://www.vstabi.de/forum1/read.php?9,17603

Gone fishing..or hunting..or something
My site: http://heli.dacsa.net - VBar videos and more

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01-19-2009 03:41 AM  9 years agoPost 5
Cheech91060

rrApprentice

Aberdeen, MD

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Tony - Are you continuing to use D=0 now that you've found this bug?
Have you had a chance to compare 0 against positive D values?
Thanks

Frank
HBFP, Trex 450, Vibe 50

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01-19-2009 09:13 AM  9 years agoPost 6
tchavei

rrProfessor

Portugal

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No, I've now put +15 and I'm itching to go to the field and do the final tests. It was already VERY good with D=0 and I=42, P=80, C=75 after I increased my tail rotor diameter almost 20mm

Tony


--------------------
"Perfection and patience usually walk side by side..."

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01-20-2009 08:02 PM  9 years agoPost 7
puma1824

rrVeteran

Maryland, USA

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After finding and resolving this bug, did this help you with your tail issues in MrMel's Road to Ultimate Tail (LINK) post?

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01-20-2009 10:01 PM  9 years agoPost 8
tchavei

rrProfessor

Portugal

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Actually I solved it the day before by increasing the tail rotor diameter by almost 20mm and putting D to 0 (I didn't knew about the bug at that time but I decided to disable D because it didn't feel right). Since then I've now corrected the value in the file (through the overkill panel) to +15. I expect the tail to be even better than it was last sunday

Tony


--------------------
"Perfection and patience usually walk side by side..."

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