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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From your video i think you have a lot of vibrations, arms too long is one of the issue...

Hi Marco,

My video is crap because of the Y650 gimbal assembled with the wrong servos.  GWS SO3N2 digital.... jumpy.  I will fly today with gimbal disconnected.

Just to show the vibrations on the airframe I post the accelerometer graph from my indoor test flight:

How does it look?  Those spikes appear when copter bounce off the concrete floor in my basement.


Those are nice and clean ACC graphs. Vibes are definitely not the problem here.

It's probably the long arms. Imagine an ice skater spinning around on her toe; the farther she holds out her arms, the slower she spins (same momentum, less inertia). In the same way having those long arms on your copter significantly increases inertia. A given prop will produce the same torque regardless if your copter has a narrow or wide stance. So you have... more inertia+same torque => less yaw rate.

To compensate for this, you might try increasing yaw_rate_P. If that doesn't work and your power system allows it, you might also try increasing prop diameter. Longer props will provide more torque. In the end, like an ice skater you might need to pull the motors in closer to the CG to achieve your desired piro rate.

Good luck with daddy long legs! ;)

Please advise... I just watched your video and the audio alone tells me your have a problem with your rate tuning. Sounds like high Rate_D oscillation to me. This has nothing to do with your yaw, but pitch/roll rate tuning is perhaps a higher priority versus increasing yaw rate. ;)

I agree with Kevin.

Likewise, your Rate_D is 0.055, set that to 0.010. You can also push your Rate_I a bit higher, maybe up to 0.150 or more. On some airframes Rate_I can be higher than Rate_P

Graham Dyer,    default rate_D at 0.010 felt so soft for my frame/motors/props...  I may try 0.050 or 0.045.

I can't see any difference tuning rate_I   with the knob on CH6.  What is the proper procedure for rate_I tuning?  Can you please point me to a page if you know which one is right.

From what I've seen Rate_D is like a dampener for when the quad returns to level from a user inputted control movement, so if you jab the roll stick rapidly and let go, Rate_D affects how quickly it returns to level, too high and the quad will drift to far in the opposite direction to the input, also high levels of Rate_D however cause a high frequency occillation and so should be kept low. (between 0.008 and 0.020)

I prefer Rate_I higher than Rate_P which gives me a firm locked-in feel and more resistance to horizontal drift and small balance issues. Try Rate_I at 1.5x Rate_P, but if you get occillations (especially in ground effect) then set them both down a bit. (I use Rate_P of 0.200 and Rate_I of 0.300, every frame is different though).

Kevin B,

yes ACC should be calm as I have balanced motor cans and props and have 2 layers of moongel under APM case.   

Torque does not turn it fast enough and I do not really want to increase YAW RATE_P  to the sky.  Idea is to be able to maintain it airborne with one failed motor and get to home location using RTL.  Currently it barely does it.  Depending on which motor failed you can yaw one way without loss of altitude and another way with spiral down.  I will address this with motors tilt.  That will give much more authority to yaw.

Good catch on Rate_D.   It was tuned to the extreme in the still air. But in the wind the arm which is down the wind behind the airframe starts oscillating a bit. Turbulence I guess. I will tone Rate_D  down a bit.  Wind was strong that day...  25+ km/h   I actually shoot the video from the ground using smartphone. That was a flight minutes before the one you saw from on-board cam.

Just read your last line but anyway.......... i would not go as much a 5 degrees on a y6 to start wiht.


What you could also do is to tilt the motors ever so slighly 2-3degrees in order to have thrust assist with the yaw and not just rely on torque from the motors/props.  i have done this on a octo and the yaw is bulletproof. DJI does the same on the s800

i have even started doing it on my quad build (they need a little more however to be effective about 5degrees.

That is right, I mentioned 5 deg from my past Quads experience.

Can I do tilt on just one boom?  Rear one.

I'm running about -3 degrees of tilt on the rear pair of motors on my non-APM y6. Motor configuration is set up the same an an APM y6. This makes all motors do an even amount of work, and makes the yaw response more even. I do have shorter arms though (600mm MTM), but my AUW is similar to yours.

Can you please explain why do u think all motors do same work with back pair tilted 3 degree?my Y6 wok just well with all motor vertical....fast yaw before was not so nice for me,in 2.9.1b is just ok...but my Y6 is a bit of a monster (5kg without camera and gimbal,14x5 or 15x4.5 props,batt is 6S 8Ah 2x1.1kg)so i dont do acrobatic and very fast flight....any information abaut Y6 is welcome bcs before i had it as a Hexa wich died one bad day bcs of 3 strong servo motors of gimbal conected to apm2 cosed brown out..today i use brushless gimbal,i dont trust servos conected to APM powerd on from input side(output side died some time ago)



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