Reduced aileron throw when in Attitude mode??
« on: August 10, 2017, 11:08:22 am »
Gents, I am trying to set my CC3D for first time for a Fixed wing, 2 aileron. I assigned a three position switch for mode Manual/Attitude/Rate. Throws on Manual and Rate (when I move the sticks) are the same. However, when I switch to Attitude mode, the ailerons barely move. I am using LibrePilot 16.09 and a CC3D board version 2 (don't know how to get the board firmware version.
Can anybody explain why that may happen?
Thank you

f5soh

  • *****
  • 3915
    • LibrePilot
Re: Reduced aileron throw when in Attitude mode??
« Reply #1 on: August 10, 2017, 11:49:58 am »
Most of the time that's the normal behavior with default values.
No issue, you can start flying with this settings.

Manual is direct or transparent link between sticks and servos
Rate, you ask for a rotate speed with your sticks.
Attitude you ask for a bank angle.

You can increase the Attitude mode response in advanced tab, eg from 55° to 90°
The Attitude Stabilization (Outer Loop) > Proportional can be increased as well but oscillations should appears quickly.
https://librepilot.atlassian.net/wiki/spaces/LPDOC/pages/19890317/Attitude+Setup#AttitudeSetup-Advancedtab

You should also consider using Rattitude or Acro+ stabilization with your  fixed wing, just try in-flight.
https://librepilot.atlassian.net/wiki/display/LPDOC/Rattitude+Setup
https://librepilot.atlassian.net/wiki/pages/viewpage.action?pageId=19890205


Re: Reduced aileron throw when in Attitude mode??
« Reply #2 on: August 10, 2017, 03:33:42 pm »
I think I may not have been clear with the problem. I can take that when the plane is in attitude mode, small throws would be used to maintain the attitude, however, when I move the sticks that should overwrite the attitude throws, isn't? I mean, in Attitude mode, if I leave the sticks alone, the plane would maintain level flight, but when I take over, shouldn't I be able to have full control? And by the way, why this restriction I am having, is only on the ailerons, and not with the elevator?
I will be looking into the links you sent me, to see if that would help until I have a good grip on this issue.
Tks.

Opps

  • **
  • 94
Re: Reduced aileron throw when in Attitude mode??
« Reply #3 on: August 10, 2017, 05:19:03 pm »
Try to pick it up switch to altitude mode and bank the plane  in all directions and see what they do. Do the ailerons have full deflections? Altituded mode only allows you to go to a predetermined bank angle.. maybe try ratitude that will allow you to go a full 360 degree rotation and will self level once your back in the goldiie zone i think anything under 65 degrees with stock numbers. Look on the exper tab  where you put pids in i think stablization. Sorry im doing this from memory. Hope this helps

f5soh

  • *****
  • 3915
    • LibrePilot
Re: Reduced aileron throw when in Attitude mode??
« Reply #4 on: August 10, 2017, 06:13:35 pm »
Quote
I take over, shouldn't I be able to have full control? And by the way, why this restriction I am having, is only on the ailerons, and not with the elevator?

There is no issue here.
In Attitude mode you don't have direct control or full control hover servos but control over the bank angle you want.
Elevator is more reactive maybe because you picked some fixed Wing profile with Pitch PID increased.

Another behavior you cannot see while on ground/not armed/Throttle to 0 is the Integral term (error accumulation) effect from PID stabilization.
In fact after you apply throttle just before launch the wing is perfectly stabilized, even in Attitude mode.


Re: Reduced aileron throw when in Attitude mode??
« Reply #5 on: August 10, 2017, 08:05:39 pm »
The reason you might need less reaction / throw than you think is that the same amount of aileron throw has a much higher roll rate at high speed than at low speed.  In fact if you think about it, for a given aileron angle, when you vary the forward speed, the roll rate is proportional to speed.  The ailerons act like a screw going though the air and the faster you push it forward, the faster it rotates.

Without some coding and setup, CC3D doesn't have a way to sense the forward airspeed, but the faster you fly, the more sensitive (in airplane roll rate for a given stick angle) the ailerons are.  If you set ailerons too sensitive you get oscillation at high speed, but OK at low speed.  So you set the aileron sensitivity at max speed to avoid oscillation and you get slower controls at low speed.

So to work really well, you need airspeed (Revo class FC) to control the aileron (and elevator / rudder (unless rudder is unstabilized)) rates for high speed.

IMO, if you have rudder in addition to ailerons, the rudder should always be manual stabilization.  If you have rudder with no ailerons (3 channel), the rudder should be set up in the FC as if they were ailerons (and use normal aileron stabilization).

Don't move the transmitter trims away from where they were when you ran transmitter wizard, or if you think you must, put them back there at the end of the flight and adjust using other methods that depend on the mode you were flying.  You can make sure your trims are correct by looking at the Input page (with battery and USB connected) to make sure the "Channel Values" match the "Neutrals" for aileron elevator (and rudder only needed if stabilized).

A fixed wing beginner without access to an instructor probably wants to jump straight to Attitude mode because it self levels.  Before first flight, you should check for reversed controls, adjust control linkages for neutral and range, verify CG, etc.  A little bit nose heavy is a very good thing for Manual mode.  It makes pitch positively stable (as opposed to neutrally stable) and it makes it so that (over the long term) adding power makes it climb and reducing power makes it descend.

You need to pay careful attention during setup that the FC thinks it is perfectly level when the airplane has wings very level and the fixed part of the horizontal stabilizer looks like a very very shallow (say 2 degrees) climb.  Set all the control surfaces to neutral from Manual mode.  I think there may be some issues, particularly if your elevator is out of trim and you have to hold constant elevator.  You may find that you need to hold more and more because this needs to be adjusted with RotateVirtual, not with trims.  Remember that for Attitude mode if you find you need to hold a lot of some control, the best thing is to quickly get it on the ground and adjust RotateVirtual before flying again.

In Attitude mode you will notice that the controls "wind up" a little once you start the motor.  Because of this, you should launch fairly quickly after starting the motor.  If hand launching, I would recommend that you hold the nose down slightly (elevator winds up "up" not "down"), but wings level till just before release.

In Attitude mode, during flight, remember that to turn it around you need to hold close to full aileron and full elevator through the whole turn.  You can reduce altitude over the long term by reducing power.  If it needs left/right trim, you might try rudder trim since it is not stabilized.

CC3D doesn't have INS13, but for people with Revo class FC's, know that the attitude level changes when you change from Basic to INS13.  Either start with INS13 so you get leveling / RotateVirtual correct from the beginning, or redo RotateVirtual when you switch to INS13, or start by calibrating so there is no difference between Basic and INS13 ("Fine Tuning Your Hover To Stop Drift (Not Required)" in https://librepilot.atlassian.net/wiki/display/LPDOC/Aux+Mag+Setup+and+Calibration).

Opinion: I find that you kind of need to be a good airplane pilot and knowledgeable LibrePilot user to set up a working Attitude mode in a fixed wing.  First flight flown manually.  Trim it out.  Cross trim it for straight loops.  Set control throws.  Then fly in Rate mode and get that tuned and working well (airspeed PIDs for Revo class, and normal PIDs for all).  Finally fly it in Attitude and get that tuned and working well.  Then if you have a Revo class FC, you can start playing with GPS modes.  A lot more work than Attitude mode with a quad.

Re: Reduced aileron throw when in Attitude mode??
« Reply #6 on: August 11, 2017, 01:31:19 pm »
Gents thank you very much for your responses.
To be honest with you, I don't feel comfortable at all with the way CC3D controls the aircraft. To start with, I will just discard the idea of Attitude mode, simply because I am good enough not to need to press the "panic button". I would like to use Rate, because the winds in south Florida are becoming quite unpredictable with speed changes from 2 to 10 mph in the blink if an eye, and landing 10ponds (4.5Kg) planes in those conditions is over my skills. Now, the way that CC3D deals with the trims, even in Rate, scares the hell out of me.
In short, the plan is to go Rate in the final approach, and see what happens. Regardless I will be looking into the Acro+ mode.
Finally, I am definitely not an expert in Libre Pilot, not even close.

Opps

  • **
  • 94
Re: Reduced aileron throw when in Attitude mode??
« Reply #7 on: August 11, 2017, 04:39:25 pm »
Maybe ratitude is the flight mode  you are looking for? It's a mixture of both altitude and rates. so when you fly it will be level if you  take your hands off the sticks, if your in a certein predeturmind degrees of angle bank (i think the stock numbers are 65 degrees). if you want to preform a very aggressive turn or upside-down it allows for 360 degrees rotation.hope it helps. There are so many functions and setting in librepilot and lifes to short  to get hung up on one thing. Just continue to test and tune also try to fly into the wind if at all possible. Good luck, hope everything  works out for you.

Re: Reduced aileron throw when in Attitude mode??
« Reply #8 on: August 13, 2017, 12:30:24 am »
Thanks a lot Wayne. Will do. Will configure for Ratitude and see how it responds. That may be a solution. And true, Libre Pilot is good stuff but mostly for those that have a good grip on it.