LibrePilot Forum

Users => Vehicles - Helicopters => Topic started by: Filippo94 on April 15, 2016, 08:14:27 pm

Title: What level of vibration is allowed?
Post by: Filippo94 on April 15, 2016, 08:14:27 pm: Today I tried to spool up the heli for the first time, but had a bad result ;D.

Slowly rising the throttle, at middle stick some "jitter" starts, and raising the throttle to max lowers its frequency. Before doing that I searched around for vibrations, but everything seems ok. Doing further testing revealed that the servos are moving strangely, without any input. To me it seems like a high frequency type of vibration causes, with an offset to the CC3D update frequency, a rotating correction.

I then paid attention to it with no blades on (tail and head), and the problem is still there. With the heli secured (AND NO BLADES!!), I kept a finger over the CC3D while testing various throttle inputs, all I can feel is a Gamepad type of rumble, there are no oscillations on the tail, which looks rock solid, before reaching about half stick, where the tail servo starts oscillating followed the same way the ciclic servos do.

It's the first "full size" RC heli I'm building, I have no idea of what's usual and what's not, but in the 120 SR, after balancing the blades, I had a similar rumble (quite lower intensity, but that heli is about 110gr heavy) and never caused issues to the gyro.

Rate or attitude seems making no difference. I have stock stabilization values, still have to take off and see what are the needs.

So I wonder, is the CC3D really picking those vibrations and reacting, or is my setup not good enough to allow any gyro activity? Would lowering the compensation gain solve the issue?

btw, CC3D is mounted behind the main rotor, right over the tail mount.
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on April 15, 2016, 11:46:48 pm: Jitters like if the throttle midpoint is too far fro the minimum? If my throttle minimum is 871 after I do Manual Calibration then I set my throttle neutral to be 873.

hope it helps.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 15, 2016, 11:50:46 pm: Nope, throttle response is all right, it's the way the servos act which looks like being interferred. They oscillate a bit, or a lot, depending on the throttle amount. For example, at mid stick it starts oscillating slowly, like when your tail gain is just a tad too high, going higher it gets more intense and frenetic, reaching 75% it is quite random, going further amplifies and goes slower, at full throttle looks like you're slowly turning your cyclic stick (mode 2) in circles.

I didn't check if stability was still working (if you don't mind, I'll leave a full throttle heli well anchored on the bench), but the stick response, in all the four servos, were crisp and working.

indeed, it looks like it suffers from resonance...
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on April 16, 2016, 01:12:18 am: I don't understand what it's doing.
video?
UAV>
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 16, 2016, 01:32:04 am: Will post both tomorrow, hopefully will be visible enough.
Does setting "Manual" in the flight mode assign the servos raw input from the transmitter (filtered through the 120° servo math)?
Maybe if I manage to keep the stabilization out of the system, I can find out if it's, indeed, a stabilization issue, or if it's a mechanical issue, even if everything seems solid and in place...
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 16, 2016, 09:51:13 am: So, here's the video (https://www.youtube.com/watch?v=AiokZG_gjMk&feature=youtu.be), and the UAV (attached). The servo motion is not that visible on the video unfortunately, but it's surely enough to cause the entire heli to oscillate while it has blades on, causing further vibrations. You can see even the tail pushrod oscillating back and foward slightly, moved by the tail servo.

Also you can see how the tail has no motions while the engine spools up (tail servo apart), showing that there are no visible vibrations. I did look even without the heli locked, and the results doesn't change.

Edit: I did tested manual stabilization for pitch, roll and yaw, after recording the video. The response is correctly filtered, but indeed has no reactions to any movement. Spooling up the heli this way, the servos do not move at all. So yeah, it's a vibrations issue. How to fix it, since the heli looks quite balanced already?
Title: Re: What level of vibration is allowed?
Post by: f5soh on April 16, 2016, 09:55:13 am: Your AccelTau value is set to 0

This means the accel filtering is completely disabled: Try to put something around 0.05, Attitude tab > Accel filtering

Edit: You can also increase the refresh rates for your servos... maybe capable more than 50Hz ?
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 16, 2016, 10:10:07 am: Turned the Accelerometers filter up to 0.2, it didn't affect the problem. Remember it happens both in attitude and rate mode.

How do I know what refresh rate my servos are able to receive? Trial and error?
I've read somewhere that digital servos should be able to handle 300hz, I did try that for the tail servo, but it stopped moving at all. Maybe I can just increase over 50hz and see what happens.
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on April 16, 2016, 12:29:02 pm: G'Day Fillippo,

Change the 1099 (throttle neutral) to 1067, Throttle minimum is 1065 now. Neutral and minimum must be close.

Do you really need your servos to react at faster than 50hz? Mine all work fine at 50hz. I have burnt up an ESC --trial and error. I have ruined a few servos, too. One digital servo, E-Flite DS76t, gets hot at 50hz and it's supposed to be a 330hz kind of servo. Go figure!

Be careful with servo refresh rates. If anything gets hot or buzzes then lower the rate.
Good luck,
Dave
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 16, 2016, 12:46:07 pm: Changed neutral throttle in inputs settings to 1067, now the engine spins always, when I'm not in hold mode, even at min value. The oscillations are still there with both Attitude and Rate.

I'm not sure if I need more than 50hz refresh rate, to me it seems enough at least to start flying the heli. Surely if I'll need some more snappy behaviour I could try go higher, but I'm sure there's plenty of settings to play with before I'll need more accurate responses than 20ms.

I just had an idea, to check the graphs from the CC3D.
It seems the vibrations it's picking are really really wide, even if I can't see them. How could it be? (remember this was with the USB attached to the board)

I started the heli in manual, so the CC3D was not moving the servos, and slowly raised the throttle up to 50%, then activated the attitude mode, exactly when you see in the attitude graph starting oscillations. Then slowed down to stop, and spooled up again, always with attitude, you can see the tail was oscillating quite a bit.

Same settings as before (except manual instead of rate for pos. 2 flight mode).
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on April 16, 2016, 01:02:04 pm: Re-do Manual Calibration of TX in Configuration. After that change the neutral to be close to the minimum. I have a feeling the glitch/jitter is caused by that setting. I set my throttle neutral really close to the min.

Board level it important to Attitude and Rattitude. And the swash seems to have different ideas if you switch to those modes without board level being perfect.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 16, 2016, 01:29:46 pm: I did like you said, now these are my new TX values (attached). It didn't solve. I discovered my throttle curve for Hold was at -10% (maybe some nitro heli precaution the Dx6I adopted?), set it back to 0%, and now the min throttle is correct even with hold off. Yet there are those oscillations.

I've checked the CC3D position, only think I could find out is that the USB port could touch the support, so I moved the CC3D a bit back, but it looks like did no differences...

Switching between rate and attitude makes no difference on the swash with a level heli, the previous graph was switching from "manual" to Attitude, which I guess could justify eventual drifts building up while Attitude was disabled.

Edit: forgot the attachment ::)
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on April 16, 2016, 01:55:52 pm: Did you recalibrate the TX with Manual Calibration after you discovered that hold was at -10%? If not then try that.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 16, 2016, 02:01:34 pm: I discovered I had hold at -10% because after calibrating the min value without the hold was really far from the min result. After fixing the config, I've of course redone the calibration. The result is what you see in that image.
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on April 16, 2016, 02:04:58 pm: Rats!
Back to vibration: have you tried the motor without anything else , even mainshaft spinning?
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 16, 2016, 02:15:32 pm: I just did, and it works, the servos react correctly, not shaking. It means even this very little vibration that the mechanic causes is not something the CC3D can tollerate?
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on April 16, 2016, 02:22:26 pm: The main gear in you video sounded rough.

Also, perhaps the tail boom needs grounding. I have heard of that.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 16, 2016, 03:08:46 pm: I have a bit of wobble on the tail drive gear, but I've read it's normal non-so-much-precise helis. Will try to reduce it.
Grounding the tail boom? You mean that it's causing a shortcut?

Edit: It's less than this one, I'd say slightly more than half than that. (I found out how to post videos!!)

https://www.youtube.com/watch?v=zdk4RjhaF-M (https://www.youtube.com/watch?v=zdk4RjhaF-M)
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on April 16, 2016, 03:46:18 pm: Yes, that tail gear is terrible. I bet that a good gear fixes you up.

And, I have heard that a tail boom ground helps keep static electricity from becoming a problem.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 16, 2016, 04:03:48 pm: Isn't there a way to raise the gyro noise tollerancy lowering the stabilization efficiency? I saw online helis with worse oscillations being able to fly pretty well, honestly it leaves me surprised to see I can't even put blades on because of resonance...

Edit: Found it, let's see if tuning it allows at least to have a working setup to test with.

Edit: Of course it didn't solve the issue...
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 17, 2016, 12:26:21 pm: I'm going to order again another spare batch for this heli. What to do if the new gear is not as straight as I need, or if it's not going to reduce the vibrations enough?
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on April 17, 2016, 02:29:27 pm: Don't worry. It will be hard to find another gear that bad. Will a T-REX gear fit?
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 17, 2016, 03:04:32 pm: I think so, the Tarot 450 has most of components compatible. this specific gear has a bit of difficulty passing through the main frame, the other one seems a bit thicker, in the worst situation I'd just have to remove one side of the frame. Only thing that bothers me is that here in Italy there are really few Align stores, and often they have not all the things needed, so I have to wait them to come here from England....

And in meantime I can not keep troubleshooting, since if the tail gear goes not in place, I can not check for other vibrations, or components needing replacement (another 10 days of waiting). One thing is for sure, I'll never buy again 2nd hand products at this level, for the "toys" in my signature it's not a big issue, these machines can get much worse than I thought instead...
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 20, 2016, 06:04:35 pm: I discovered a shop which had everything I needed, today the new gear arrived, it's much more straight, close to perfect, and with also a different tape under the CC3D, most of the issues seem gone. I'll try now to balance the tail blades, and then the main blades again, hoping to see no oscillation from the CC3D ::).

I've also noticed that if I don't lock the heli, the vibrations on the servo are much lower compared to when it's locked. Maybe the support on which it is mounted amplifies the vibrations? Where should I clamp it to test?
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 22, 2016, 07:19:23 pm: I'm really starting to wonder if it's better to trash the whole project.
I've balanced the blades multiple times, checked everything that could cause vibrations and tried to fix as much as I can, Still without blades I get a slight resonance that I can see only through the correction of the CC3D, and with the blades I get really dangerous wobbles close to 50% throttle and after, if the heli was not clamped to the table it would have exploded touching the ground in a few seconds. Tracking is just perfect, I can't distingue the two blades looking at them on a side at low RPM. This board is just ridicously sensible to any kind of noise, and at this point seems the only thing preventing me from flying the heli.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 24, 2016, 12:45:21 pm: Looks like the vibrations now are low enough to use the filters, when the wind will calm down will finally try to fly it. Right now it still tends to tip over at take off. I need a proper space where to fly it, where I can give it a good push to raise it in the air, instead of being scared to give pitch in this little area...
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 24, 2016, 11:19:50 pm: Today the heli had finally a maiden flight! :D

Accelerometers are responding well, but gyros (tail's more visible/investigated) are really really sloppy. I tried raising the P to as high as I could without oscillations, but the tail keeps being quite oscillating when giving input/stopping it. If I raise it more it starts oscillating. I have some play in the tail I have to get rid of, but the behaviour of the tail seems not correct to me.

I surely have to do further tests, and tweaks, but right now, do you have any tip on how to solve it?

Ah, this is in rate mode, with heading lock it seems to always want to correct user's input, maybe it is indeed trying to keep heading direction like if it had a compass?

I tried to place the heli on a flat surface and to compensate the inclination of the CC3D in the attitude panel (due to irregular bottom, the board is not perfectly level on the stick sponge tape). Though with Attitude mode the heli as a visible drift. Is there a more effective way to zero out the inclination of the board, or is it better to just not try to compensate it? Also, is there a way to change the Attitude's inclination target? Helis tend to not be deadly horizontal to have a stationary hover, due to the tail rotor generating a lateral force. A solution is to keep the heli a bit tilted (usually to the right). Is that possible to be accomplished, without having to make the board think it is not level?

Here's the UAV file (the middle flight mode is just for vibration tests, it has its own switch)
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on April 25, 2016, 02:54:18 am: Horrray! A maiden flight!

Don't worry about fixing the tail slop mechanically. I have two HKs that have 10-15 degrees slop. The tails are great. That is what PID is all about, que no? I don't have fast servos either. My friend's Trex 250 with the really, really tight tail linkage does NOT fly better.

Don't worry about "board perfectly level" If you fly in Attitude or Rattitude then it may becomes important.

I see you have one mode set for Rate Trainer. How is that?

I fly in only Rate , Rate, AxisLock for tuning. I try Bank 3 first. It has the highest PID numbers that might cause some oscillation. I can switch back to Bank 1 in flight with one easy switch if it gets squirrelly. If I try Bank2 I can switch back to Bank 1 from there very easily, also. Bank 1 has the lowest numbers but if I like the way Bank 3 flies I make it the new Bank 1 and adjust Bank 2 higher and Bank 3 higher still. Repeat. If Bank 3 flies good save time and don't try Bank 1 or bank 2. Swap Bank 3 into Bank 1 and raise the values until you see oscillation on each axis.

Also I adjust Yaw neutral value until it hovers 'hands-off".

Try that with yours. You can get close to good PID numbers faster that way. Too bad we have only 3 settings Banks...
Look at my PIDs . My I values are just over 50% P.

Today I ran a few packs through Amarillo doing just that. It is really good. I like it. I may experiment with Rattitude, Attitude, Vbar and Acro+ on Amarillo just to learn how they feel after I get the other one, Blackie, doing something autonomously.

BTW if you got 5 TX modes I bet you can do 6. Adjust endpoints of both inputs to fine tune.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on April 25, 2016, 12:34:27 pm: Yes, I can get 6, this is the topic where I explain it: https://forum.librepilot.org/index.php?topic=1413.0

Thanks for the tail slop, that'll save me some moneys :D

I do fly Attitude at the moment, it helps me controlling the heli while I do tweaks, as right now the heli responds in a quite unprecise way, this helps me keeping a referement while flying. When will be finished, I'll switch to rate, and start tuning that, knowing that if things get wrong Attitude works and can save my heli. Will just eyeball the tilt of the board based on the result of the attitude zero position while flying, like they are trims. Right now with stick at zero position the heli drifts quite fast back and left. The way I adjusted it right now is placing the heli on a horizontal surface, and looking at the telemetry setting numbers untill the board thought to be level. Clearly this "scentific" method did not work, so I'll go for the good old Try and error :P

I've set 4 flight modes, just thinking a way to use more flight modes, I have Attitude and Rate Trainer as a switch combined with "up" position of one other switch, and Rattitude and Rate as the results of the first switch combined with "down" position of the other switch. Just like having an aggressivity switch :D. Since they're close together, it needs my finger to just switch up both to fastly jump into "panic mode" activating Attitude. Right now I can not trust Rate too much, since the gyros still need tuning.

I also discovered the heli had no power enough to keep the tail straight (giving max right yaw barely moved the heli on the right), I figured out the tail servo neutral position was to be set not centered. This should be specified though, it's.... the third time, a "center" position has not to be in the center, this is starting to get quite confusing honestly.

I keep the 5th flight mode as manual, just to check the vibrations of the heli when I swap blades, or just want to be sure about resonances. once my tuning session is over, I'll remove that from my TX, so I will not activate it on accident, yet I can reuse it without having to get back to the netbook.

Thanks for the banks suggestions, I just assumed they all were the same, will try like you said.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on May 01, 2016, 09:53:31 pm: So, this sunday was my 2nd day of flying the heli, this week I did absolutely nothing.

Unfortunately had not the possibility to record a video, but I finally discharged my first lipo in one go :D.
Was a pure joy, incredibly stable, even though it had yet some oscillations, and a such cheap hardware to fly with.

So, the banks showed to me the same exactly settings between each other (of course the first one had my settings). Today I worked on setting Attitude to be as reliable as possible, and same for the tail. So far I came out with a pretty solid tail, which doesn't hold the position with pitch pumps though, I'll have to do further investigations. Rate was the tail setting.

Attitude has a strange behaviour instead. I managed to get a correct "center" to hover the heli, the cyclic response is pretty snappy, up to oscillating if I esagerate, but even so the speed with which it returns to self level target is pretty slow, seems like not having it at all when attempting fast flights. It does center, but takes a few seconds even from a slight bank angle. Seems also to slowly oscillate a bit around the center, like a ball rolling toward the bottom of a bowl. Is there any way to get a faster "centering speed"? Raising P causes it to oscillate even more when I suddently change bank angle. I really like it though, makes flying really interesting compared to what I expected from it.

Rate works, but has not been tweaked, I just checked it responds good enough to handle the heli.

I also managed to lower the noise filter for the gyros, but I saw that the adviced max value for noise is 0.02, I have it around 0.05, was at 0.15 to get rid of resonances on the bench tests ::)...

Next things to do: try and check HeadingLock for Tail, get a snappier response from Attitude, configure Rate, getting rid of the various oscillations that occour on the tail at different flight speeds.

I'll keep attaching my progresses on the settings, so who is interested in checking it maybe has something to learn. BE CAREFUL, I'm not an example of who knows everything ;)
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on May 02, 2016, 01:49:27 pm: Great! A good gear and it flies. I hope you get it tuned to your liking soon.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on June 13, 2016, 01:50:44 am: Hello guys! It's me again.
On Sunday 8th of May I had my first crash due to a wrong cyclic setting, and decided to use flight modes in a more "educative" way. I've set them to be Attitude only, with a switch to change between yaw rate and HH, and a switch to change between setting banks 1 and 3. This way I can take off and land using bank 1 settings, which I know for sure they work, and in flight switch to bank 3 to test my settings. Still no crashes from that day :D.

So, right now the heli feels pretty snappy in Attitude, and tail is quite Ok, but the compensation to pitch "smashes" is still quite bad. It's good enough to safetly fly around, approach the ground and stop the "falling", but if I insist a bit more the tail drifts of about 30 degrees before returning to its position (with rate being less precise than HH), and if I push to max pitch (which I did not measure yet) and max throttle, the heli does over 450 degrees of yaw turn before returning still (with rate mantaining its position, and HH trying to go back a bit).

Now I'm in a situation where the tail slightly oscillates already, and rising P causes these oscillations to get worse, but helps compensating. I seems to not sort much effect when changed, and D is not helping that much either. While flying foward at medium-low speed the tail oscillates more, but keeps its direction.

Now the tutorial I've followed says to raise gain untill it starts oscillating, to raise I to compensate external forces untill it does start to over-compensate, and to use D to lower the oscillations when snappy stops occour.

I got that the tail compensates badly the pitch pumps, that it over-compensates a bit my snappy inputs, and that oscillates slightly when still, and more evidently while flying. What have I to do in such a similar case?

Also, the Yaw settings of Attitude, what they refer to? There's no Attitude for rudder (I guess there would if the cc3d had a compass). Does it refer to Heading Hold? It does not work like I expect a yaw Attitude to work (example: heading Nord, stick to the left heading West, stick to the right heading Est). Do I have to take it into account too? Right now I didn't touched it.

I attach the last .UAV I've exported today, note it may have wrong attitude horizontal settings, and that bank 3 settings are surely the last I used to fly.

Thanks once more for your help :D
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on June 13, 2016, 12:27:04 pm: You must be flying well to land it with a tail that imprecise. I have trouble with a tail moving 10 degrees. I am spoiled.

You have huge steps between Bank 1 and Bank 2 -- yaw
bank 1 <field values="0.00300000003,0.00499999989,0.000150000007,0.300000012" name="YawRatePID"/>
bank 2 <field values="0.00999999978,0.0299999993,4.99999987e-05,0.300000012" name="YawRatePID"/>
bank 3 <field values="0.00639999984,0.0299999993,0.000300000014,0.300000012" name="YawRatePID"/>

I usually make much smaller changes. Perhaps: bank one .00300 bank two .00310 and bank three .00320 and keep D about the same proportion on each until I get close and then try different D values with P constant. When I get a good D then I go back to P and refine it to three decimals -- (0.00324 maybe).

Both your Roll and Pitch are the same . Do you have roll and pitch linked? I linked them to get started but quickly found that since the roll axis has a different polar moment than pitch axis they need different PIDs, too. MY D numbers end up just over 50% of P instead of 200% that the Wiki recommends.

It looks like you are using AxisLock and Rate on the tail. Both work well for me. I have not tried anything else on Yaw. I didn't know they offered Attitude on Yaw??? I use Tail Mix in my DX7S for compensation. I must add 24% at full collective to get good pitch pumps. Without it I get about 30 degrees of tail swing.

I notice also that you are using the default "220" Manual Rate. I set mine to flip and turn much faster. At 540 my heli can do 1 1/2 flips in one second and thus behave just like my little Blade helis. At 220 degrees / second I would probably need 10 meters altitude to flip without crashing. If you change the 220 to something higher then lower your PIDs to match.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on June 13, 2016, 01:23:22 pm: Remember this is my first 6ch heli, and that right now my main goal is to keep it in the air ::).
The only issue I have with it is how much fastly it gains speed, and in the very little place I have to test in, this is quite an issue, so I have to keep the heli quite slow.

Bank 2 is unused. I have Bank 1 set where the last time I got good results, and keep changing only bank 3. Once I'm happy with bank 3 (idk, got more precision without oscillations) I copy the settings from bank 3 to 1, using 1 as a "Saved settings" bank, where instead the 3rd is constantly changed. My typical flight consists of Take of bank 1, get in the air, switch to bank 3, do pitch pumps and snappy yaw inputs, eventually switch back to bank 1, land, go to netbook, change values, repeat. :-\

Yes, I have both collective linked, right now I got enough control of the cyclic, but can't quite well understand what's going on with it untill that tail stops being so imprecise, it makes the whole heli wobble when it is in crysis, so I've stopped there for cyclic, since it sort of works, and am trying to tune out the tail.

Tail has no attitude setting indeed, but the Attitude P/I settings have a yaw parameter, so I wondered what was its goal...

So you also have not found a solution for the tail to hold its position under changing loads? That's disappointing, I expected LibrePilot to be able eventually to get there, and gave to me the fault of not being able to tune it the right way. I guess will ask devs if they have implemented it, or if they plan to. Will try tail compensation on the tx to fix the issue, only with rate, right?

Manual is not used, I have it there to test eventually how the heli is responding without having the cc3D stabilization in the way, to see if the servos are responding . I use it on the bench only :)

Thanks for the answers, will test your suggestions... next sunday ;
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on June 20, 2016, 08:24:10 pm: So yesterday I tried using the revo mix on my Dx6i, but had no luck. The heli knows exactly where it has to be oriented, indeed adding the revo mix, in both Rate and Axis Lock, the heli was not straight again when I did a pitch pump. I honestly do not know anymore what to do about the tail.

I also had an insight. Since the tail seemed to be neutral with the pitch slider being too much close to the gears, thus allowing just a tiny amount of right rudder available, I tried switching the tail grip direction, and to reverse the tail servo aswell. Now the pitch slider sits much closer to the center (it's closer to the blades rather than to the gears now), but tail holding capabilities didn't get any better. I keep having the tail oscillating slightly at the center, and I can hear it swinging while fast flying, but if I lower the gain the tail becomes uncontrollable, recovering from a dive is really dangerous with low gain.

So in the end I reverted to no revo mix, and will keep the tail like so, hoping one day to find a solution :-\.

Right now the heli feels pretty good, still using Attitude, it's snappy and precise (apart from the tail's problems). Next sunday will move onto the cyclic, trying Rate mode and setting gyro gains better, and also I hope to have some wind to test external forces compensation.

I really feel the need of a governor for the engine, can't get a proper curve to keep revs at the same, now that I'm actually flying the heli ::). I guess it'll be the first upgrade I'll buy to it.
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on June 20, 2016, 09:51:54 pm: Yes, I have a tail on Blackie that I must work on. It is not precise. My other HK250, Amarillo, and the Trex250 for my friend both are great. But Blackie is not right yet. I will share what I learn about Yaw on Blackie.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on June 27, 2016, 12:07:15 am: In the forum where I asked about specific mechanic infos and suggestion during the building of this heli, I've also asked if they have experienced similar tail issues with the CC3D. Someone pointed out I might have too low RPM.

So I redid the collective calibration using the pitch curve of the CC3D (now at min-max 12°, before was higher) and prepared the TX to use a full Idle-Up flight mode, with a V-Curve 100-80-100 for engine and of course -100 100 for collective. Did not dare doing any aerobatics, but the tail did hold much better this time. it still has some drift when punching, and yet some oscillations while flying, but now seems to be better. Of course battery did last less ::).

Tried also setting finally the PID for Rate flying mode, but keep having a few issues: While roll feels pretty snappy and precise, it tends to lightly oscillate before holding the position when I give a sharp input. I've read it should be fixed by adding D, but it amplifies the problem instead. Pitch does that aswell, but it's a much slower oscillation, really looks like a flybar overcompensating. if I use too much high D on Pitch it oscillates much faster like Roll when snappy manouvres happen. Both seem to be at the highest P possible before oscillations in hovering.

For now I just lowered a bit D on both, but had not much time to do further tests. I've changed the flight modes now to use Attitude with bank 1, and Rate with bank 1 and 3 (last edits on 3). I did found out that the settings for Attitude are too lose on Rate, and Rate settings are too strong for Attitude. Maybe I just have to go back and tune Attitude again when finished with rate, I've the sensation I just used accelerometers in Attitude, and now that the Gyros are set more correctly they both overcompensate if put together.

Also did some little tune to the tail, but today I wanted to focus on cyclic instead. Will attatch the last exported settings, if someone is curious about them.

I'm really pleased with how this is turning out, the CC3D seems to be really the right choise for me, I only need more than two hours per week of testing...
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on July 04, 2016, 03:05:13 pm: Some little updates:

On the tail I noticed I had too high D, which was the cause of the oscillation. Now I managed to double P and to dampen it using half of D I was using before. Have to further investigate though.

I did some flips and tic tocs to see how the rate configuration is. It's rubbish ::). The heli doesn't hold its orientation at all during these manouvres, I know some compensations are needed, but this was simply too much. So have still to optimize rate settings. The tail instead holded its position pretty well, which helped a lot saving the heli :D

Not much progress honestly, I did mostly enjoy the heli this sunday 8)
Title: Re: What level of vibration is allowed?
Post by: TheOtherCliff on July 06, 2016, 12:37:58 am: When you get PIDs set as high as possible, it will track the sticks better during quick maneuvers.
If the head speed is too low you can get issues like that too. Use the recommended head speed and tune PIDs to that.
Also, be aware that there is another stabilization option that is similar to Rate. It is called AxisLock. Within some range of angles, it will put it back where it was if it gets off during maneuvers. That range of angles can be made larger for bad cases.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on July 06, 2016, 01:56:49 pm: I did these maneuvres with a V shaped curve 100 - 80 - 100, if more headspeed is needed then I'll need new electronics...
Yes I know about Axis Lock. Is it advisable to be used on the cyclic? I did think about it, but was unsure if there are some not intuitive consequences. I've read in some old topics about HeadingHold gyros, some people was saying that on the tail could not be desiderable when banking for example, as the HH gyro would not let the tail naturally follow the banking. I did try this, but feel much more confident with AxisLock than Rate on the tail, but wondered if there could be stronger unwanted results using it on the cyclic.

Will try it the next time though, let's see if it actually makes flying better :).

Thanks for the suggestions! ;D
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on July 18, 2016, 04:08:34 pm: Hello! Last sunday had a TT issue, so couldn't test much, but this sunday I did some tests with AxisLock on cyclic. It seems to hold much better, indeed I was able to do a flip on the spot this time :D.
This however did also show me how bad the tail holding is, since when I was out of the flip, without any input on rudder (and again quite a lot of cyclic work) I got out with more than 50° of difference compared to when I entered.

I did fly a bit the 120 SR in these days, which is a fixed pitch heli with tail motor, and the tail holds much much better compared to the heli, even when giving sudden throttle increases. Of course it fails sometimes compensating in the tightest turns, but that's the little motor not having enough strength, which should not be the case on a TT driven tail.

I attatch once more the UAV, where this time I've setup the flying modes to take advantage of the banks. In my last fly I was testing radically different I parameters, since while flying with the wind or without wind I still didn't understand when I comes into play. And still can't notice any difference, I thought it helped with compensating external forces, but while the tail holds pretty well its direction in hovering, if I try to ask for more pitch it starts immediately drifting. Right now I still have a slight oscillation, but in pitch pumps it still drifts quite a bit. I even tried putting P up to 0.01000, but apart from getting much higher oscillations, it did not improve tail holding abilities while pitch pumping.

by the way, when giving pitch pumps the engine speed increases, the pitch is not enough to load that much the engine, which I remember works on a 100-80-100 curve. So I'd expect the tail to get more authority in this occasion, since its RPM raises...

Does it really end here? There's no solution for the CC3D to hold my tail? Will I have to search for another FBL board? Or am I the one which is completely uncapable after so much time to set his heli?... :-\
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on July 18, 2016, 07:04:24 pm: Relax. Any tail can be tamed. Somewhere I saw advice to raise the D when you have trouble getting P & I to work. I have done that. Then I lowered it back, too, when I got the to the root of the trouble.

I had one, Blackie, that was tough to nail the tail down although two other 250's were easy to get the tails right. I had to get very close with the P & I numbers before it started to behave! With three settings banks incrementing P upwards from probably .00230 where it was sluggish by units of .00003 or .00004 until it got close (and keeping I about 53% of P). Then at about .00265--P and .00140--I the increments became .00001. Likewise and independently with I. Now : .00266--P and .00139--I and it might not be done. Blackie's UAV from 2 weeks ago: Yaw .00286--P and .00144--I was mushy AND it didn't oscillate like you'd expect.

Vibrations are the enemy. Maybe vibes are causing gyro troubles Does your tail fin vibrate?

You can balance heli dynamically with spectral analysis. Info on this thread: http://www.rcgroups.com/forums/showthread.php?t=1996241 .

To balance: Start without main hub, main blades blades, rear rotor blades and maybe no rear grips to check torque tube. Add a part, check the wave forms (and your own senses) and balance. It helps my tiny bl mcpxs and ncpxs greatly. It took me a while to learn to use this tool but it is worth it. All of my helis fly better balanced.

My Spektrum TX has tail mix, sometimes called revo mix set at 42% at full pos or neg pitch. 21% halfway.

You are right. Changing rpm complicates things. For throttle settings try 90, 80, 90 or 100, 90, 100. Adjust from there to your liking. Amarillo's throttle is set at 76, 74, 71, 74, 76 because I can't hear it speed up if I set it higher. I am guessing 4,000 rpm headsped. And Blackie's throttle is at 41,39,38,39,41 but may go higher if I balance the tail better. It shakes the fin.

LOOK AT THAT! I JUST SAID IT! Writing this for you is cathartic. I am going to go balance Blackies's tail better now.

Thank you,
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on July 19, 2016, 04:05:33 pm: That Earbud trick is just awesome ;D, will try to build one and see if it helps.

I have an oscillation at low RPM, which disappears with higher speed. The tail fin does not vibrate, but I've seen in particular situation close to the ground the broken landingear vibrating. Will do some reserches with that earbud approach. Did you tune P first, up untill it started to oscillate, and then tuned I? Or did you tune both?

I do use quite a lot of D to dampen the really high P values. This narrows the oscillation, but seems to cause another oscillation when set too high. Do you use higher P and then dampen them with D? Or do you just use D to make the controls snappier?

Also, what do you think a good explanation of how PID works is? I've looked at some explenations online, some simplistic, some more complex, but both seem to not help me when tuning the heli. Where did you learn from?

Thanks for your assistance, you really are precious for the heli users in this forum. Without you, I would still be angry at why my servos shake when spooling up the heli ::)
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on July 21, 2016, 06:11:56 am: I did a little more balanceing on Blackie's tail. It looks solid in my back yard. I raise the headspeed so I will readjust the PIDs.
Tomorrow I will try to get some real flying with Blackie.

Once I tried some automatic tuning (I forgot the name) and it assigned I values a bit over 50% of P values. I stick with that pretty much. When I get really close with the "P" then I mess with the "I" hoping for improvement.

Here are the PID definitions that I work with: P== Proportional-the amount of push I == Integral --brakes for when it gets near the target and D== how often it checks and corrects.

you are welcome and I am glad to help
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on July 21, 2016, 07:29:15 pm: Ok, the headphone trick was close to useless for me, couldn't really get any consistent results out of it, and thus was too hard for me to compare different spectrums to check for minimum difference. My finger was much more precise than my brain ::).

Also decided to mount on the Align blades instead of the "pro3D" ones which I have, since it seems I am not able to tune out the unbalance of them. the vibrations are further reduced now, will see on Sunday how will it perform.

I don't think I can use Autotune, it seems it requires at least a knob or a slider to tune the values on the fly, which my Dx6i does not have. Maybe it would have been much easier if I actually had the possibility to continuously test multiple values without having to land each time. The best I have is to try different values on the banks and switch them, but I keep having difficulties reaching the sweet spot, it seems like I can get closer easely, then I oscillate around some value which seems right, but both increasing and decreasing it causes more oscillations or sloppiness, without having one actually not causing oscillations and keeping the tail still during pitchpumps...

I am not sure of your skill level with heli flying, but if you are used to do some 3D, can you actually perform 3D manouvres like flips, funnels, tic-toc, without having the fear of the tail swinging away? If you perform such manouvres with Axis lock on all the axis, do you easely get out of them with minimal correction?

On the sim I can perform such manouvres without much difficulties (yes, I keep having some issues with orientation 'cause I did skip the basics, which is the main reason why I tend to avoid doing them with my heli), and have tried messing up the gyro values on the sim to get a sloppier tail, and started encountring the same difficulties I have with the CC3D, exiting from flips with a different orientation, even if the tail returns to holding position when the flip ends, of course the direction it is trying to hold has shifted during the flip, resulting in lost heading.

Maybe I should restart from the beginning, using low P only and tuning that first without oscillations...
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on August 01, 2016, 12:16:51 am: So, last sunday I just saw a better performance due to the new blades (decided to use the new ones instead of the old ones, mainly because these were much more balanced out of the box, and were not covered in tape to get balanced), redid all the pids, but did not go too far, so had nothing to report.

Today instead there was a strong gusty wind, which kindly showed me where I was doing wrong, and thus allowing me to correct the behaviour much more precisely.

Now the cyclic is nearly perfect, it was holding its pitch and roll quite well in the strong wind, with a roll axis really fast and snappy, without oscillations or delays, and a pitch axis which oscillates when I send snappy inputs, but otherwise being pretty much as effective as roll.

Tail did not get much better, but at least it seems a bit improved aswell.

At this point the heli feels much more solid, and ready to be used as a trainer or just for fun (not much, since I'm not a good pilot), soon will post my values in the excel sheet you've created, for a beginner is a really cool starting point.

untill then, this is my last UAV, with nearly completed cyclic, and "working" tail.

Thanks again for your support :D
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on August 01, 2016, 01:14:51 pm: I am glad you got it going better. Isn't it good when it flies well in the wind??!!

Just curious. I looked at your UAV and saw curve2 source like this:
<field values="-0.75999999,-0.400000006,-0.0399999991,0.330000013,0.689999998" name="ThrottleCurve2"/>
And my curve2source is : < -1.0, -0.5, 0.0, 0.5,1.0 > !?!?

I don't think you will get full pitch-- either positive or negative.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on August 01, 2016, 03:16:47 pm: Seeing the heli not caring for the wind while I can pacefully train myself is pure pleasure ;D

Yes, I did set it like that to get, if I remember right, 12 degrees of pitch in both directions. Already this way pitch + cyclic is enough to largely lower the engine's RPM while doing one of my clumsy flips, which you can imagine makes the tail even less effective. When I'll get the heli completely working I'll get back to the pitch and experiment with it, but for now I have more than enough push to save myself in case of danger, without killing the engine. Since I didn't want to "dirt" the setting of the Dx6i to get the right amount of pitch, I decided to use the CC3D itself to save a parameter which has the same importance of the servo calibrations, or response time. Just seemed more tidy to me, to group the heli setting all in the software, and let the pure flying configuration on the tx itself.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on August 08, 2016, 12:46:32 am: Making some progresses! ;D
Today I did finally get a good tail, good enough to be able to see finally my progresses into the simulator being transferred to my heli exactly like I expected.

After having seen this video

https://www.youtube.com/watch?v=y1hjVZq1VNY

I decided to go straight to choose the highest value of P that could be dampened with the right amount of D, and then add a bit of I of the needed amount.

It did work much better than to increase P up at the first hint of oscillation, then adding I up to not get over-corrections, and D to stop the oscillation of the snappy inputs.

So I decided to do a recording again, to show how much stable now the heli is (even if my pilot skills suck enough to hide it). I did take off, and landed, with attitude, and also used attitude in a case to save the heli, since I'm more confident with that, but otherwise everything else is in AxisLock. In the flight I mainly focus on all-directions hovering, but also do some pitch pumps, two flips, and a really shy attempt at inverse hovering.

https://www.youtube.com/watch?v=AfQ1eaOrn2Q (https://www.youtube.com/watch?v=AfQ1eaOrn2Q)

In this week will add the current values to the excel, since now the heli is secure enough to fly without loosing control.
Now, the next urgent upgrade to do is an ESC with governor, since I can not get over the compensation differences between a fresh battery and a nearly discharged battery, the tail gets much looser at the end of the battery, and needs tighter settings, which of course cause oscillations once the new battery is plugged... Once having that, I'll keep making further optimizations to the values, having a constant RPM will surely help a lot.

Thanks once more for the help you've given to me :D
Title: Re: What level of vibration is allowed?
Post by: daveapplemotors on August 10, 2016, 02:35:08 pm: It looks pretty solid in the air. You certainly have a small place to test fly there.

I am glad you have it flying so well.
Title: Re: What level of vibration is allowed?
Post by: Filippo94 on August 10, 2016, 05:19:21 pm: Yeah, unfortunately it is already around 32km away from home, and it is the closest I can get for now :-\