Help needed regarding arducopter crashes

Hello. I have assembled an arducopter. The specifications are given below.

jdrones default frame (with foams attached under arms)

Configuration: Quad X

APM 2.0

880 Kv Motors

12x45 propellors

Futaba 10CHG

The frame was assembled as per the wiki. The ESCs have been calibrated as per the wiki. Props were attached properly and balanced. The accelorometer calibration were also carried out as per the wiki.

The modification that was carried out was just the attachment of foams under arms. Since i was new to the flying, so i wanted to save the arducopter from crashes which i experienced initially. The 4 foams have a total weight of 126 grams.

3690978439?profile=original

The pid parameters were adjusted to counter for the heavy motors and sensitive controls. Rate_p and Stab_p were changed. The parameters file is attached.

parm_of_quad_at_first_flight.param

The arducopter has a tendency to move away from its position after take off. I only alter the throttle input and after it rises to some height it moves away from the point from where it was taken off. May be wind should be considered but that was not enough to move it from the center of a football size ground to almost its end in stabillize mode.

The arducopter also has a tendency to lose altitude sometimes. After it has been taken to a certain height in stabilize mode, the copter loses altitude without any throttle. Though it should have been put in ALT HOLD mode for this purpose, but even in stabillize mode it should not lose altitude of 6-10 meters. Once i took it to about 10m, it was in stabilize mode and after some time it started losing altitude to an extent that when it was about to land i cut the throttle and made it land.

Another major problem that i am experiencing is that it flips over without any other input other than throttle. It happened once in ALT HOLD mode (crash 1, video and tlog file attached below) and two times in stabilze mode (crash 2 and 3, video for both and tlog file for crash 3 attached below.)

crash 1 - 2012-12-11%2010-49-59.tlog

Arducopter crash 1 - Flipover Video from Majid Khan on Vimeo.

Sorry. Don't have a log file for crash 2

Arducopter crash 2 - Flipover Video from Majid Khan on Vimeo.

crash 3 - 2012-12-11%2014-13-20.tlog

Arducopter crash 3 - Flipover Video from Majid Khan on Vimeo.

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Replies

  • Hi Majid,

    I'm having a similar problem and am trying to get to the bottom of it by comparing your configuration with mine.

    BTW, I admire the foam cushion design.

    Can you share a little more of your thinking on why you reduced the RATE_PIT_P from the "stock" setting of .17 to .1 ?  

    I wonder what you mean by "heavy motors and sensitive controls" because the specs on your motors and props look fairly standard.

    I'm thinking (admittedly without full understanding) that when RATE_PIT_P is reduced without reducing RATE_PIT_I, the emphasis on the historical error increases.

    (Unlike your situation, my flips have been occurring after making several sharp turns.  To eliminate hardware as a factor, I'm replacing my APM, ESCs, and motors.)

    David

  • Try a smaller propeller, perhaps 11inch, to help rule out motor stall.

  • me too had the same crashes, and today when i was trying to tune my arducopter by holding it in my hand to get a feel of the parameters i changed, i got the reason of my crashes. One of my motors stopped for no reason!!

    this was not something that i expected but, it was in my hand i gave it some throttle tried different controls. gave some disturbance inputs by moving my hand and all of a sudden one of my motors stopped. i repeated this thing several times and sooner or later and some times much later the same motor used to stop. 

    now i know my Quad crashed because of motor stopping in flight BUT i don't know why the motor stops!!!

    is there something wrong with ESC or motor or what, idon't know. 

  • After seeing your video, I have had 2 similar instances.

    One was after 3 auto flights, on the 4th between the 3rd and 4th waypoint my copter flipped just like that.

    The second time was when I was using ground station to change modes from loiter to stab. I clicked the button to go to stab on GC (flight stick was neurtal) and the copter just fliped.

    The 1st flip was exactly like your video.

    The 2nd flip was like it was powering through an actual flip maneuver.

    Havent been through the logs yet tho.

  • Hi Majid,

    I've been having sudden flipovers too.

    The first time was in stabilize mode.

    The second time was in LOITER mode, and I got video and log of the second crash.

    Video here: https://www.youtube.com/watch?v=pHqjheOdlbs

    May I know if you have anything attached to CH6 of the APM2?

    I have my DX7's transmitter's (2-position gear switch) ch5 inputting ti CH6 of APM2. If the input is high, I get random quick twitches every 3 to 10 seconds, if the input is low, the quick twitches do not happen, but now I have this sudden falling out of the sky problem. When I repair, I would be trying with nothing connected to APM2's CH6.

    2012-12-15 11-51-04.rlog

    2012-12-15 11-51-04.tlog

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