Replies to This Discussion

Permalink Reply by dr1ce315 on July 19, 2012 at 7:00pm

We have used a tachometer to read all the engines while running and when enough throttle is applied for the unit to lift we're getting ~43k RPM on the front 3 Motors, and ~55k on the rear 3 motors... 

Is this a firmware problem?  PID?  Any help would be appreciated =)

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Permalink Reply by Cliff-E on July 19, 2012 at 8:13pm

Check motor axle lengths from the CG/center. Check motor mount tilting/bent.

On the software side, minor roll/pitch on take off is usually a leveling issue. If you auto-leveled, then your APM is way out of physical tolerance--physically level the board and run the level command (don't auto-level).

Also, not liking your GPS mount position. Get it up and away from the Rx.

And... are those Aircraft Spruce AL booms? I just got them for my Y6 repair and they are very nice pieces (and 6037 AL).

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Permalink Reply by James on July 20, 2012 at 11:52am

PID tuning is to control the change of attitude, to get it following your stick or autopilot inputs quickly and smoothly without too much oscillation.

if its consistently pulling forward in stabilize, then its because it thinks its not level.  if the level is good enough to fly with then the in flight level (with no wind) will give you the best results.  if not, then level it on the ground first, it looks new so your landing gear is probably still square, but the important thing is to level the motors.  i do it with a spirit level between prop spinners, then invoke level either through mission planner steup (if using a usb cable make sure the cable isnt pulling APM off its resting position) or with the radio holding disarm for ~10 seconds.

james

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Permalink Reply by dr1ce315 on July 20, 2012 at 3:05pm

Well, we just tried to check if the board was not level for some reason.  We put a 2x4 in the front and leveled it and tested, and it still pulls forward.  We then put the 2x4 on the back leveled it, and it is still pulling forward.  (the 2x4s were removed while testing)  Wouldn't that prove that leveling isn't the issue?

Could the board be bad?  We had it flying with some different motors and props in the past.  Could it be the firmware?  Would a firmware downgrade, and going back to MP .9 make sense?

We're really pulling our hair out here and have been fighting this problem for over a week...  We have factory reset the board and re-uploaded the firmware, done all the leveling and radio calibration several times.  I'm the computer guy, and my friend is the RC expert.  He highly suspects the firmware, and thinks his build is quite solid. 

At this point I'm thinking 1 of 3 ideas: 

1)  Get another APM Board and make sure the gyro or board isn't defective in some way.

2)  Downgrade the firmware

3)  Change it to a quad and see if it works in that configuration (with the quad firmware of course), which shouldn't be too hard.

This has been an expensive and mind bending experience, and help would be appreciated.

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Permalink Reply by James on July 21, 2012 at 1:52am

i dont know if there could be an error with the upload of firmware to the board, but if youve reset, tried again and got exactly the same result it shouldnt be the problem.  the v2.6 firmware for hexa flies absolutely great in my experience, so i would keep looking for a config or motor problem.

im sure youve checked this, but the default frame orientation is "X", if you havent set it to "+" that could cause this kind of problem.

how about changing the motor signal wires, if you swap the front three motors for the rear motors do the front motors now run faster than rear?

james

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Permalink Reply by m00se on July 23, 2012 at 12:37pm

Im new to this, BUT,

have you calibrated all esc´s the same? have you checked that there isnt a bad motor somewhere on the front ?

i had this problem and it was a motor that appeared to work but was drawing more current than the others and thus not spinning as fast at the same throttle level,

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Permalink Reply by dr1ce315 on October 26, 2012 at 1:11pm

We're still struggling with this rig.  We've put a brand new APM 2.5 board in it, thinking it was a gyro or accelerometer or chip problem.  The firmware has been reloaded/reset 20 times, brand new manually calibrated ESCs...  The data from mission planner seems to suggest the board is putting out incorrect PWM to the ESCs...  

Can someone please help?  I've attached the data log for the last two "attempts"...  It just keeps pulling to the forward right no matter what with just straight throttle applied...

Attachments:

• 2012-10-25 13-07-56.tlog, 124 KB

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Permalink Reply by James on October 29, 2012 at 3:19am

although its been mentioned further up, theres no definite reply about auto level, so ill go into it again.

although youve levelled on the ground, theres no reason for this to give you a perfect level for flying.  an error of just a few millimetres will make it drift towards the lowest motor.

the most reliable method is to use the in-flight levelling: hold the arm motors position for ~20 seconds then take off and fly in no wind maintaining position as best you can over a point on the ground.  use tiny nudges on the stick to move the calibration to a perfect level - once calibrated land and disarm.

having tried more than one APM, and new ESCs it seems very unlikely to be an electronics problem.  if its not caused by being off level the only other thing that comes to mind would be a vibration problem causing "the leans"

james

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