Motor spin slow than others

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ben November 14, 2015 at 10:21am

Hi, I've just figured out I have the same issue here ( GE260 folding frame with mini APM 3.1 controller )

- Motor#3 ( back left ) spins slower than others at low throttle commands ( approx less than 30% )
ESC and motors are soldered, so I really can't swap them for testing, used to shorten previous #3 ESC one year ago .. replaced it, everything was fine using FLIP32 controller, issue appeared as soon as using the Mini APM.. thought it was some PID settings misconfiguration at first glance ..

I did recalibrate the ESC then ( 4 at the same time ), at "slow" takeoffs the quad flips over itselfs in the #3 direction .. with a quick "40% throttle burst" the motor #3 will behave like the others, allowing a regular takeoff, stabilized, everything's fine ..

Until I want to reduce my altitude, it most of the time results in a destab into #3 avis, then the quad reacts, bring it back, and destab again in quite a "funny" dance which ends only I if i use the pitch / roll command or throttle up a little bit .. everything's fine again

At some points, it might lead to a crash ( as testing RTL , the AltHold mode, sometimes has baroglitches, resulting to altitude drop, same #3 issue and crashes this way, or at lower battery levels, it never compensates enough the motor #3 glitch and crashes again .. )

- Here's a basic scheme of my problem :

Thanks for any help, notes, ideas ;)

Cheers :)
- Dennis Megarry > ben January 25, 2016 at 5:27pm
  
  I too am having this issue with the Mini APM Pro on Motor 3! All motors spin at the same speed when armed, but motor #3 only starts spinning up at 1/4 throttle.. I moved the PWM wires to another prop connection and it ran fine, but any motor connected to #3 spins slower.. it is most likely a bad APM.. Bought mine off Amazon and left bad feedback for the seller.. I did not opt to return it because I like its size and everything else seemed to work ok so will try it out in a plane where only one prop is needed.
  
  I did notice an issue that if I arm it and the props are spinning slowly, it will automatically disarm if I don't try to power them up.. not sure what that is all about. If I run the throttle up and then back down, it will stay armed.
  
  I fooled with this thing far too long, got to try something else now.. Going to put my Pixhawk in it to see how it does.
  
  Tarot 650 Sport
  
  DJI E800 Propulsion
  
  Nano-Tech 8000mah 6S battery
  
  Atto Pilot 180A for battery monitor
  
  5v BEC powering the APM
  
  RFD900 Modem
  
  DragonLink (Copter version)
- Dennis Megarry > Dennis Megarry January 25, 2016 at 6:39pm
  
  Think I figured it out.. Still a bad APM though..
  
  When I lift the APM while in stabilize mode and wobble it around, nothing happens.. Though the artificial horizon in MP does move..
  
  I put in a regular APM 2.6 and when moved around all the motors go nuts adjusting RPM's while in stabilize mode.. Odd that the artificial horizon is getting input from the gyro but not the motors.. I checked, rechecked and triple checked to make sure I was in stab mode.
- Dennis Megarry > Dennis Megarry January 28, 2016 at 5:42pm
  
  Solved the issue of the one motor not spinning up as fast.. I tried EVERYTHING, just about every firmware old, new and beta I could find with no luck.. I installed a regular APM 2.6 on my frame and everything worked fine.. ARGH!
  
  Then I save it's parameter file and wrote it to the Mini APM Pro.. it fires up and all motors spin as they should, a lot smoother even! and plenty of power.. They max out at a lot faster RPM now.. Maybe this will help someone else.. Wonder why this happened? Wouldn't a new firmware install replace all the parameters?
  
  I'm attaching my file n case you want to try it..
  
  dennis.param
  
  https://storage.ning.com/topology/rest/1.0/file/get/3702806898?profile=original
- ben > Dennis Megarry January 30, 2016 at 12:18am
  
  Hi, except PID tuning and radio's trimming here are the main differences with mine :
  ( did this with np++ excelent compare plugin .. )
  
  BAROGLTCH_DIST    250 500 ( yeah I do have some baroglitch appearing, and hate having them in auto / rtl mode -> this causes altitude loss and further unstabilities )
  ARMING_CHECK      1      0     ( arf )
  
  DCM_CHECK_THRESH    5=>0.8
  EKF_CHECK_THRESH     0=>0.8   ( put it to 0 because this caused me auto-mission to land in the trees once waypoint one reached )
  
  THR_ALT_P                   0.4 => 1 ( had huge stability issues when loosing altitude, some flips etc .. leaded to previous crashes )
  MOT_SPIN_ARMED       0=>70
  POSCON_THR_HOVER 461=>513
- Hollis Inman > ben January 2, 2016 at 8:47am
  
  Did you have any luck figuring this out? I've had a similar issue... my faulty position will actually cut out completely if I lower the throttle too quickly.
- andi azhar > Hollis Inman January 9, 2016 at 8:04am
  
  its seems new diy builder having the same problem, hehe, i face it too, and still searching for the solution, omg
- Khoa Vu > ben November 22, 2015 at 10:39pm
  
  @Christian, just moved on to page 2. Do you have a flight log file? I think some of our developers can help you out. Also, have you tried getting new firmware? Hope you get the guy flying soon!
Cristian Rougier April 30, 2013 at 2:47pm

HELLO i checked in status and channel 4 output is lower than other channels.

I tested in low and high speed, Please see the attached images.

Can you help me to correct this please?

Regards

Cristian

channel4_at_low_speed.png

channel4_high_speed.png

https://storage.ning.com/topology/rest/1.0/file/get/3692702548?profile=original
Cristian Rougier April 30, 2013 at 8:53am

I changed all ESC's to CX-ESC-40A , and the problem persist, motor 4 spin slow

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