Warning #1: an issue has been found with Tower's Pause button which can cause the vehicle to fly to an old position if the vehicle has not sent a position update to Tower in some time.

Warning #2: Copter-3.3.2 fixes a bug found in Copter-3.3.1's desired climb rate initialisation which could lead to a sudden momentary drop when switching from Stabilize or Acro to AltHold, Loiter or PosHold.

Warning #3: Copter-3.3.2 fixes an issue found in Copter-3.3.1 which could lead to hard landings in RTL or AUTO if the WPNAV_SPEED_DN was set too high (i.e. >400 or 4m/s) and/or the WPNAV_ACCEL_Z was set too low (i.e. <100 or 1m/s/s).

Warning #4: a bug was found in Copter-3.3 which could cause a sudden crash if you abort a Take-off initiated from a ground station.  Video description is here.  The bug is fixed in Copter-3.3.1 so we recommend upgrading.

Note #1: AC3.3-rc8 corrected a long standing bug in the HDOP reporting.  HDOP values will appear about 40% lower than previously but this does not actually mean the GPS position is better than before.
Note #2: if upgrading from AC3.2.1 the vehicle's accelerometer calibration needs to be done again.
Note #3: set SERIAL2_PROTOCOL to "3" and reboot the board to enable FrSky telemetry like in previous versions.
Note #4: the wiki will be updated over the next few weeks to explain how to use the new features

Copter-3.3.1 is available through the mission planner.  The full list of changes vs AC3.2.1 can be see in the ReleaseNotes and below are the most recent changes since AC3.3.

Sadly this version (and all future versions) will not run on the APM2.x boards due to CPU speed, flash and RAM restrictions.

Changes from 3.3:

1) Bug fix to prevent potential crash if Follow-Me is used after an aborted takeoff

2) compiler upgraded to 4.9.3 (runs slightly faster than 4.7.2 which was used previously)

Changes from 3.3-rc11:

1) EKF recovers from pre-arm "Compass variance" failure if compasses are consistent

Changes from 3.3-rc10:

1) PreArm "Need 3D Fix" message replaced with detailed reason from EKF

Changes from 3.3-rc9
1) EKF improvements:
    a) simpler optical flow takeoff check
2) Bug Fixes/Minor enhancements:
    a) fix INS3_USE parameter eeprom location
    b) fix SToRM32 serial protocol driver to work with recent versions
    c) increase motor pwm->thrust conversion (aka MOT_THST_EXPO) to 0.65 (was 0.50)
    d) Firmware version sent to GCS in AUTOPILOT_VERSION message
3) Safety:
    a) pre-arm check of compass variance if arming in Loiter, PosHold, Guided
    b) always check GPS before arming in Loiter (previously could be disabled if ARMING_CHECK=0)
    c) sanity check locations received from GCS for follow-me, do-set-home, do-set-ROI
    d) fix optical flow failsafe (was not always triggering LAND when optical flow failed)
    e) failsafe RTL vs LAND decision based on hardcoded 5m from home check (previously used WPNAV_RADIUS parameter)

Thanks for your testing!

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That explain why I have the issue only some times, specially in first fligths and no always.

During first test I take off in stab, try to hover and switch to pos or alt hold, there the copter loose altitude that correct with quick raising throttle not to crash. Normally what I do is to take off in stab but switch to pos-alt hold when the copter is still climbing and there I don't have problem, then I land in pos hold and switch to stab again; it's sounds logic?

Thank's Piers to post your issue.

that is SO the opposite of what I do and always have done. I "never" take off or land in any flight mode except Stab. EVER. Unless I am running a mission or set it to RTL.

I "always" take off in stab and then if I want to set it to alt-hold or loiter I get it up to where I want and then flip to the flight modes. I also never "fly" in loiter as that is not what that flight mode was designed for. I just find no fun in fly by switch. If I wanted that I'd probably just buy a phantom or some DJI gear. 

What I have found is you need to pay very close attention to where your throttle stick is at when you hover in stab mode and then go to mission planner and make sure your mid throttle is set as close to that as possible. Config/Tuning/Basic Tuning/Throttle hover.

If your manual hover is blow 50% stick [over powered] and you do not set this value to your actual stick value then when you are zooming and flip to another flight mode with your stick way above 50% and then switch to back to say stab it will drop like a rock.

Same goes the other way around, if you are under powered with your stab hover stick above 50% it will tend to zoom in the air when you flip back out of say loiter.

Most of my birds are well over powered so I have to make sure my throttle hover is set to around 400 [depending on which bird I am flying] and I never have unexpected dives or zooms in the air :)

I always take off in alt hold so there can be no surprises. It is what it is already and your aware of how the copter holds altitude with the baro and stick position. If adjustments need to be made this is the case regardless of what mode you take off in. But at least taking of in alt hold reduces the risk of a surprise altitude change. 

If it's windy I fly in pos hold as I am still flying it yet it has the added safety feature of 'sticking' to where I put it. The devs have done a fantastic job fine tuning this mode I see no reason not to take advantage of it provided one is already familiar with the reliability of their gps etc, I think Dji had the upper hand in flight characteristics until copter 3.2 and the addition of pos hold,,,  after that it's never even been close. 

I second the alt hold for takeoff and landing.  Always used stabilize until I started autotune and later versions of arducopter.  Guess my manual tunes were always a bit soft.  Now it's pretty easy to bounce on landing with the really big rigs, especially on pavement.  Never loiter though, no need for an unscheduled haircut.

Craig: that depends the use and conditions were you flight, I fly in pos hold monitoring crops in FPV and taking photos, perhaps a Phantom can do it too but I like to diy my drone and get busy the second day with a phantom GLUP!!

Hello Everyone,
I'm doing some test with some new multirotor.

I have problem with land detector.

This is the video.
Attached to this post the log.

Can you find the problem?

AC 3.3 Stable on VrBrain 5.


Hi Andrea,

Could you please do an accelerometer calibration and set your log bitmask to 157693 and do this test again. This should give us the logs we need.

I think you've stumbled onto a little loop hole in our landing detector logic.

The THR_MID is very low (only 300) and the THR_MIN is quiet high (200).  This means the throttle out can never get to 1/2 of THR_MID (i.e. 150) so the landing detector won't work.

So I think either THR_MID should be raised (to maybe 400 although it depends upon the frame) and/or THR_MIN reduced (130 is the default.. it must be brought under 150).

THR_MID and THR_MIN changed. Problem solved =D Now I can land my copter in the correct way.

Thank you very much Randy, you solve everything (=

Hi Leonard,

An update on this. I have done some manual tuning on Roll using the Dave C method. The results are ok but I note a couple of things:

Roll_P needs to be quite high for good response, its much too soggy otherwise

Roll_I set to the same level results in unflyable oscillations.

So I conclude that autotune will never be able to tune this copter if it sets Roll_P == Roll_I.

Roll still feels less responsive than pitch. Not sure how I can improve this. I'm also going to try go back to simon K to see what different that makes (but with active braking enabled).



Copter-3.3.2-rc2 is available through the mission planner's beta firmwares link.  Changes are in the release notes but here they are along with a video showing the major reason this version is out.

1) Bug fix for desired climb rate initialisation that could lead to drop when entering AltHold, Loiter, PosHold
2) Fix to hard landings when WPNAV_SPEED_DN set high in RTL, Auto (resolved by using non-feedforward alt hold)
3) Reduce Bad AHRS by filtering innovations
4) Allow arming without GPS if using Optical Flow
5) Smoother throttle output in Guided mode's velocity control (z-axis now 400hz)

Any testing that people here could do before we push it out as the official release would be greatly appreciated!

I've drastically improved roll responsiveness by upping ATC_ACCEL_R_MAX. Autotune had set this to a very low value (53000), I increased it to 180000 and now the copter feels much, much more responsive.

So the $1m question is if I now try autotune on this - which actually feels pretty good - will it make it better or worse?

Too much wind at the moment to try it out!

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