Discussions

Need help with hexa tilting on take off

Posted by Shamir on September 29, 2011 at 10:26pm

Hi Guys,

 

I'm having a terrible time trying to get my hexa to lift straight off the ground.  At this moment, it wants to tilt forward on take off, so I have to stop it right away from tilting over.

 

I have made multiple posts on the troubleshooting page for AC2.  I'm willing to pay $50 to whomever helps me get this off the ground.

 

Please read a few of the posts by Don(me)on the following page for more info about my problem.

 

http://code.google.com/p/arducopter/wiki/AC2_Troubleshooting

 

Thanks

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Replies

  • Shamir October 1, 2011 at 10:15pm

    I got it!!!!!  I flipped the ESC wires around, enough to make sure it was still spinning in the right direction.  I want to thank everyone for their suggestions.  Mike, thanks for the multiple quick responses.  Can you give me your paypal address if you have one.  Your solutions at least got me thinking in the right direction.

     

    Thanks.

  • Shamir October 1, 2011 at 9:32pm

    Hey Guys,

     

    I've done most of the suggestions.  Nothing has helped so far.  The thing I have noticed is that the motor facing forward is always the first to stop when I let go of the throttle.  It seems that it's spinning slower than the rest, and that esc is hot, while the rest are not.  Does this provide any clues?

     

    Thanks.

  • basshead September 30, 2011 at 3:42am

    Have you done a hand test? If you hold the hexa in your hand or suspend it from a rope, it becomes easy to see what the problem is. If this all works, when trying to lift off correct for the ground effect with pitch/roll until you get about a foot off the ground, then you should be ok.

  • Developer
    Olivier ADLER September 30, 2011 at 1:20am

     

    Wich ACM version are you using ?

     

    Check this :

     

    - use ACM version 2.0.45

    - check radio input inside Mission planner radio view, if it is not right, switch to the ArduPPM encoder firmware.

    - frame balance and center of gravity position

    - motor tilting, should be not more than +/- 0.5 degree. use a test jig to check this. not possible to test with propeler in place.

    - each motor thrust at 100 % throttle using a servo tester. You should not get more than +/- 5% difference.

    - leveling (use a precision level and check the level inside Mission Planner instrument view)

     

     

    I had your problem on my hexa. It was because of the pitch and roll I parameter in the PI loop, causing a tilting during slow take off if not set to 0.

     

    Did you try to make a faster take off ?

     

    You should be able to make a slow take off, even with 2.0.42 if you issue roll / pitch stick corrections; you need to precisely watch the frame inclination tendancy during pre take off phase to success with this method.

     

    Or use ACM 2.045 who do have the right I parameters to make slow take off.

     

     

     

     

     

  • Björn Geir Leifsson September 30, 2011 at 12:23am
    Also check the motor axle set screws ( in the "bell" of the brushless motor). If one of the axlas has come just a tiny bit loose it can severely affect the thrust of that motor.
  • Shamir September 29, 2011 at 11:17pm

    Forgot to mention I left the battery on the floor, while it was still connected.  It had enough wire to just sit there.

  • Shamir September 29, 2011 at 11:00pm

    Hi Jason,

     

    Both are at 0 when I refresh the params.

     

    Thanks.

  • Shamir September 29, 2011 at 11:00pm

    Hi Mike,

     

    I'll take a few shots of the hexa and maybe a video of it while trying to take off.

     

    I took out the battery which was facing forward/backward, and it seems to have moved the balance around.

    It doesn't tilt as much forward, and if I hit the throttle, I can get it off the ground about a foot, but it goes forward while doing so, so I quickly let go.  Is forward movement normal on take off?  Or should it go straight up?

    I will be trying the rest of your suggestions.

     

    Thanks.

     

  • Developer
    Jason Short September 29, 2011 at 10:39pm

    Does it feel good in your hand when you power it up or does it continue to want to pitch over?

    Also, set Rate_Roll_I and Rate_Pitch_I to zero in the planner.

     

    Jason

  • Moderator
    Michael Pursifull September 29, 2011 at 10:35pm

    Don/Shamir,

     

    I read your comments. Do you have photos or video of your hexa?

    Please make sure it is balanced. A quick check of the frame can be performed by holding it lightly by each arm pair. As you hold each pair of arms, see if it tips to one some or another.

    Write down which way it its for each pair of arms, then move on to the next pair of arms. 

    When you are done, analyze what you have written to determine which side the hexa is heavier, and move components and/or add coins to the frame to balance it. Then repeat, until you have it perfectly balanced.

     

    Please report your progress and what the hexa does after it has been balanced.

    For testing purposes, expect that the craft will do unusual things while near the ground. 

    For better testing, consider using a hanging, weighted harness. Hand the hexa from a string and run the string up and over to another location, and weight the end of the string so that it takes up the slack of the string.

    When starting your motors, let it throttle up until just before it wants to lift off, then raise the hexa up off the ground, holding it well in your hand, and increase the throttle such that the hexa is well clear of the ground. Increase the throttle until the hexa is able to stay at that point in the air without you holding it. Observe its behavior. 

     

    Cheers,

    -Mike

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