Hello to all
I build a big X8 and i suspect some think happen with my PIDS when octo starts it feels unresponce with big corrections and hard landings result and some flips whatever i do in P doesn’t affect the system
I enquiry the LOG
Any comments are welcome
youtu.be/VW37goiZcRg
Link of log file is https://www.dropbox.com/s/nlj65eufdoc024n/39.rar?dl=0
Also this is my auto analysis of the log file
Log File C:/Users/Akonstas/AppData/Local/Temp/tmp7323.tmp.log
Size (kb) 11489.6279296875
No of lines 143560
Duration 0:25:40
Vehicletype ArduCopter
Firmware Version V3.3.2
Firmware Hash 7f16e4d6
Hardware Type
Free Mem 0
Skipped Lines 0
Test: Autotune = NA -
Test: Balance/Twist = NA -
Test: Brownout = FAIL - Truncated Log? Ends while armed at altitude 4.49m
Test: Compass = FAIL - Large change in mag_field (87.27%)
Max mag field length (607.88) > recommended (550.00)
Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = FAIL - ERR found: CRASH
Test: GPS = GOOD -
Test: IMU Mismatch = GOOD - (Mismatch: 0.39, WARN: 0.75, FAIL: 1.50)
Test: Parameters = GOOD -
Test: PM = NA -
Test: Pitch/Roll = NA -
Test: Thrust = NA -
Test: VCC = WARN - VCC min/max diff 4.647v, should be <0.3v
This type of copter is hard to tune. I would shutoff the lower props and make it a Quad copter and see if you can get it to fly that way. Then maybe switch to the lower props and try that before putting all 8 online.
Mike
[quote=“iseries”]This type of copter is hard to tune. I would shutoff the lower props and make it a Quad copter and see if you can get it to fly that way. Then maybe switch to the lower props and try that before putting all 8 online.
Mike[/quote]
Dear friend
Thank you for the answer but pixhawk suppose have routines for x8 the problem is dont understand this behavior also motors on arms must work together to improve stability
Regards
i also add some pictures of the esc s etup i just notice one esc has strange marks on it look at it
I have not built this configuration but I saw some discussions on this type of build and the problem seems to be with the prop wash from the top effects the bottom props. In one case they indicated the bottom props should be smaller than the top ones.
Mike
Just trying this issue up, Sorry could not make the images link.
Below is the topic posts relative to this issue:-
http://ardupilot.com/forum/viewtopic.php?f=111&t=14475
antkon:-
[quote] Strange Crash
Hello to all
Can someone analyze why my X* crashed i suspect problem in compass and probably problem with internal compass[/quote]
http://ardupilot.com/forum/download/file.php?id=4759
tabascoz:-
[quote]Hello Antkon
Besides your compass interference are high, I don’t think that was the cause. I would suspect that your PIDs aren’t adequate
[/quote]
[quote]Test: Autotune = NA -
Test: Balance/Twist = NA -
Test: Brownout = FAIL - Truncated Log? Ends while armed at altitude 4.04m
Test: Compass = FAIL - Large change in mag_field (60.66%)
Max mag field length (1014.14) > recommended (550.00)
Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = GOOD -
Test: GPS = GOOD -
Test: IMU Mismatch = NA -
Test: Parameters = GOOD -
Test: PM = NA -
Test: Pitch/Roll = NA -
Test: Thrust = NA -
Test: VCC = WARN - VCC min/max diff 5.207v, should be <0.3v[/quote]
[quote]By the logfile , in the last few seconds, starting on line 48.5K it looks like the copter has wobbled hard on roll axis then a brownout occurred. Did the batteries got ejected ?
How did you tune your PID parameters?
Also your vibration levels are pretty high. I don’t think that was the cause either, but it could bring you problems.
Could you describe what happened? Did you tape that?[/quote]
download/file.php?id=4763&mode=view
ACPUK:-
[quote]Re: Strange Crash
Looking quickly at the log, there are a lot of instances there the actual pitch is opposite to the Desired pitch.
This would indicate to me either the motor / prop setup is back to front or the AMP is facing the wrong way.
I will have a better look at the logs later…[/quote]
antkon:-
antko, further to telephone call please see attached images:-
1st is the x8 copter level full throttle.
2nd is the x8 copter with throttle mid.
3rd is the x8 copter throttle idle.
Note the motor levels.
I also sent you some high res images of Pitch forwards, Back, Roll Port, and starboard.
I hope this enlightens you, and helps clarify some confusion.
By my calculation the U10 100kv 28" on 6 cell @13kg is not enough to hover the rig. What will happen is the copter will wobble about and the pixhawk will not be able to stabilize the copter.
This could explain the diverse Roll/ DesRoll and pitch/DesPitch part we discussed.
Also you need to solve the hud issue, for your reassurance that the IMU is working.
I hope this helps for now.
Regards
Anthony
I spent some time today testing an under-powered X copter. Well I loaded it up to be hoist to simulate under power and had very similar results as to this issue.
Unfortunately when I got back in I found no sd card in the FC!!!
if i have a chance I will do it again tomorrow with logs and T-logs for you.
But it did look VERY like your issue.
It was only an X4 not a X8 coaxial.
I also need to look into 3.3.2 as I got no “No SC Card” warning.
[quote=“ACPUK”]I spent some time today testing an under-powered X copter. Well I loaded it up to be hoist to simulate under power and had very similar results as to this issue.
Unfortunately when I got back in I found no sd card in the FC!!!
if i have a chance I will do it again tomorrow with logs and T-logs for you.
But it did look VERY like your issue.
It was only an X4 not a X8 coaxial.
I also need to look into 3.3.2 as I got no “No SC Card” warning.[/quote]
good morning mate
FIRST OF ALL
thank you for your precious effort and help i just read all the emails and post here and i wait your emulate feedback i also recheck my esc and looks normal but theyu cannot accept above 6S batteries so i think i must change it and go to 12S for maximum power ,reagarding this i am thinking t-motor flame 80A 12S but
if you have anythink better to purpose by your experience i am happy to hear it.
Regards
I have just looked again at the log, and note the AP has all the motors mostly on full power. indeed they are actually clipping to max very often. this is a definitive sign there is simply not enough thrust to lift the copter.
The motors want to be able to hover the copter at a decent altitude with the PWM at 1500.
This is something we all should have spotted earlier on.
On 6S with your 28X8.2 blades the top 4 motors at FULL power will generate 2.2Kg thrust.
The lower 4 will generate around 1.8Kg thrust.
All 8 motors running flat out in “Ideal conditions” will JUST about lift 16KG on a good day. this combination will just lift your 13KG but will not be able to maintain hover let alone stability.
This is the Advantage of a phone call. After it you pick up much more relevant details and things start piecing together.
T-Motor Flame 80A are designed for these motors and run up to 12S.
MayTech 50A HV are cheaper and not too bad at all.
KDE XF 75A HV are also very good.
It’s not the current you are too concerned about its the voltage. Remember this copter should only pull about 35-40A in total. That’s 5A per motor. Therefor a high voltage is what you are looking for. These motors and blades on 12S will pull 15A MAX no more.
Hope this helps.
I had problems with a 1300mm X8 using U8 motors and 6s packs. Fixed it with 8s packs : ) Note about Tmotors, they don’t play nice with KDE esc’s. Ask how I know lol. I ended up using the Foxtech’s new 80a HV esc’s that work great.
I try to decide KDE esc has anyone here experience with my U10 motors?
I use KDE motos with Castle ESCs. We experienced major sync issues with the KDE 95A ESC that could not be resolved with any settings. First time engaging autotune = loss of sync. Castle ESC runs cooler, weighs less, datalogs internally, and never ever loses sync.
Depends on what Castles you’re talking about. The multi-rotor four pack, for lower KV motors, in a word, sucks.
They work fine for 580kv and over, but I got 380kv motors to carry a 6S rig and at that point had nothing but trouble. Switched to a DYS BLHeli…that was even worse (I had a 40 percent failure rate on those). Then got some Hobbywing Xrotor 40A and haven’t had an issue since (hexa 800 frame size).
Had almost the same issue: viewtopic.php?f=80&t=12038
The issue was solved by turning around one reversed propeller and much PID-Tuning 