[daveapplemotors]

Great! A good gear and it flies. I hope you get it tuned to your liking soon.

[Filippo94]

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 .

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

[daveapplemotors]

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.

[Filippo94]

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 ;

[Filippo94]

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.

[daveapplemotors]

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.

[Filippo94]

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...

[Filippo94]

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

Not much progress honestly, I did mostly enjoy the heli this sunday

[TheOtherCliff]

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.

[Filippo94]

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!

[Filippo94]

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 .
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?...

[daveapplemotors]

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,

[Filippo94]

That Earbud trick is just awesome , 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

[daveapplemotors]

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

[Filippo94]

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...