APM Copter 2.9.1.b has been released to the Mission Planner and is also posted in the downloads area.
2.9.1b is a maintenance release incorporating changes to 4 default parameters that have been optimized since 2.9.1 was released.  There are also 4 minor bug fixes.  There are no code function changes or additional features.
The changes are:
1) reduce default INS_MPU6K_FILTER to 20hz
2) reduce InertialNav Z-axis time constant to 5 (was 7)
3) increased max InertialNav accel correction to 3 m/s (was 1m/s)
4) reduce yaw_rate P default to 0.20 (was 0.25)
5) bug fix for alt_hold being passed as int16_t to get_throttle_althold_with_slew which might have caused problems if you climbed over 320m.
6) bug fix for throttle after acro flip (was being kept at min throttle if pilot switched out of ACRO mode while inverted)
7) bug fix to acro trainer to do with roll correction 
8) prevent cli from being entered more than 20seconds after reboot.
Users are recommended to:
    Update Mission Planner to 1.2.41 and
    Update their flight code to 2.9.1b from the Firmware tab on Mission Planner. There is no need to go through a new configuration process in the Mission Planner.


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Here my set of parameters for this "cosmetic" release, it's preferable to start with the default but not mandatory, but is important change the parameters mentioned in the first post (point 1/2/4).
I remind that after the introduction of the inertial control is very important to eliminate any abnormal vibration from your setup.

Thanks to the whole ArduCopter T

Bests, Marco


but is important change the parameters mentioned in the first post (point 1/2/4).

In my case the mentioned parameters changed automatically with the update.

Best, Markus

In my case the mentioned parameters changed automatically with the update.

This only happens if you have never changed them from the default.

When APM stores parameters in EEPROM, it avoids storing parameters that are set to the default value if they have never been stored previously. This means that if a default changes, then users who have never changed the parameter will automatically get the new value. If the user had at any time changed that parameter, then their previous choice is preserved.

Cheers, Tridge

I note, that you have the time constant for GPS versus inertial set very low (3 versus the default 5). Now I'm one of the people who have been having odd 'spike' movements in the loiter, and had tried turning this up. However seeing your low value, I tried this, and just had the best loiter I've had since 2.9.1 came out. 9 minutes 'hands free' with about 10 feet of total horizontal movement, and a foot of vertical.

Interesting, since it suggests that either this value is not working as described, or that the spikes are not coming from the GPS.

So why did you go down on this parameter?. Were you having spikes in the movement?.

Best Wishes

I took 2.9.1b out for a quick test today.

My main objective was to test whether the leniency in this edition would allow a decent flight with really bad vibes in my frame...

Like this..

So here it is flying, please watch it in HD if you can this gopro has no zoom, so it's a speck at times.

I'd say it's flying very well indeed.

I've taken the tape off the props now, and will try some auto tomorrow if the weather holds.

All good so far though. 

I really need to learn how to fly like this.  That looks like so much fun.  I still barely change my yaw direction if I don't have to. :)  Got any tips? 

i can not find the Mission planner 1.2.41 in the downloads section, where is it?

@Dave C: i love it! :-)

I have noticed that the 2.9.1b has a "V frame" feature for quads (in the "Arducopter Level" screen). Is there any documentation about that? I have a TBS Discovery and perhaps the new feature is made for "spider shaped" frames like this? At the moment I use the X quad option but with special angles (like documented here and here).

All the best, Markus

The way I learned how to free my yaw thumb was to fly around myself and never stop moving my feet so that I could always reorient my body. What really helps it to keep walking around while you are flying and yaw directing the copter. It seems that when you keep moving your body around it helps to break the problem with staying oriented with the craft. After some practice you can fly fast small circles around yourself like a plane on a string if that makes sense.

Looks like the V frame is setup for a 45/135 arm angle quad, and it's giving more "control power" to the motors on the back since they're closer to the frame.  From AP_motorsquad.cpp.

// V frame set-up
add_motor(AP_MOTORS_MOT_1, 45, 0.8877, 1);
add_motor(AP_MOTORS_MOT_2, -135, 1.1123, 3);
add_motor(AP_MOTORS_MOT_3, -45, -0.8877, 4);
add_motor(AP_MOTORS_MOT_4, 135, -1.1123, 2);

As for 2.91b, it's working fine on my disco.  I'm still fighting old APM demos that are related to how stabilize mode works.  I think I'm just going to fly in acro all the time.

That reminds me I found moving around in stabilize with wind (it was gusty, up to 20+ mph at times) made my copter very unstable at times.  I think I can tune more of it out, but it was clear variations in wind + control input was causing problems. 

I felt that lowering Stab_KP made it more stable in wind, but at times would greatly limit my control to move around in the wind, while raising stab_KP gave me more control but caused more problems.  I would normally adjust Rate_KP in the opposite direction of Stab_KP.  

The key issue I see is that  people will tune for no wind, and have some major problems with wind. For example, in a hover with no wind on my quad the following settings would hover the same.

  • Stab_KP = 3.5 and Rate_KP .120
  • Stab_KP = 5 and Rate_KP .100

That's just a hover but actually flying showed different problems when flying and with wind. 

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