Hi.
I have a problem after updating AC to 3.2.1 from 3.1.5.
When in Loiter, the the speed of the motors rev up and down/pulsate quite rapidly. This was working fine when I was using previous versions of arducopter.
I have downloaded the logs, and have looked into accX, accY and accZ. These seems to be inside the range specified in the wiki at arducopter. (Log_vibrations.bin)
Please have a look at the Log.bin, and note the difference between ThrIn and ThrOut when I'm in Loiter mode.
Anyone having any idea what the problem may be?
Replies
Congratulations "piku"!
While I am waiting for my new motors and props, could you do me a favour? Please make a short flight in Stabilize and Loiter/AltHold and upload a graph showing ThrIn, ThrOut and AccZ - similar to the one I made i my first post. Also a log would be great, then the developers should have a better chance to investigate when time allows. There is only a handful users reporting this issue, so I guess it does not have high priority at the moment... no problem!
Note:The jumpy throttle curve in Loiter may be normal, and may not have any relevance to the unstable behaviour in autonomous flights. That's why I am interested in the graphs I am asking for.
Regards Jan
Hi
I have all ready updating, (before few days), my quadcopter from 3.1.5 to 3.2.1. I have the APM 2.5. After upgrade the firmware calibrate(radio, mag) and tuning again my quad with new pids. I do not have any problem in alt hold and loiter.
In this test video ( https://www.youtube.com/watch?v=NfSjY6YQh8s ) i used loiter, drift alt hold and rtl after agressive flight with any problem but you cannot see. :)
So I have hexa F550.
t-motor 900kv
esc dji 30a opto
apm 2.6
props 9x45.
Guys can you upload graph with thr in/out ? I think this is not a vibration problem. My friend have a 250 quad. He have horrible vibrations and althold works fine. I think the problem is under/over load + pid's.
Some graphs from my tricopter:
- Mini APM V3.1 ArduPilot Mega
- Motor: 3 stk. RcTimer 4215-460kv
- Servo:Towerpro MG995
- ESC: RCTimer 30 A
- Battery: Turnigy nanotech 5Ah - 3s
- 650mm motor to motor
- Props: 14"x4.7" APC
- AUW with 5Ah battery: 1760g
I have tried both the latest firmware Arducopter 3.2.1 and 3.1.5. For this test I used 3.1.5 which was marginally better than 3.2.1.
From the graph it looks like the tri is a little underpowered (ThrOut~620), that is because the setup was designed for 6s batteries - running 3s at the moment as the ESCs cannot take 6s). The tri behaves normal in Stabilize, but in Loiter and AltHold it is jumping around. From the graph I can see that in Stabilize mode the ThrOut is matching ThrIn perfectly, but in Loiter and AltHold the ThrOut is pulsing.
The AccZ is not great, but well within limits +-5.
Motors with higher kv, RcTimer 5010-620kv are under way, better matching the 14"x4.7" propellers on 3s batteries (or perhaps 12"x3.8") - hopefully this will take care of the pulsing motors. Any thoughts?
Regards Jan
This second graph is from an earlier test with Arducopter 3.2.1, enclosed is also the corresponding log file.
2015-03-27 APM 3_2_1.bin
JHIN, I noticed that your Throttle PIDs are also at the default. Have you tried tuning them?
One thing that is different between 3.1 and 3.2, is that the default Throttle PIDS changed. If a parameter is at the default, then it will change with to the new default setting when you change your firmware. If you have changed a parameter, it will remain as it is.
So anybody who is going back and forth between 3.1 and 3.2, while their throttle PIDS are default, will see the effect of this change. The issue could simply be that the default pids in 3.1 are closer to correct for your system than the 3.2 defaults.
It is impossible for us to find one default PID setting that works for all machines. This is why they need to be tuned for every machine.
Rob,
You nailed it!!
And it is embarrassing! With Arducopter 3.1.5 - after gradually changing "Throttle Accel" P/I from 0.750/1.500 to 0.500/1.000, and "Throttle Rate" P from 6.000 to 3.000 - the pulsing is gone. Just a very small disclaimer - the wind calmed down during testing... I noticed earlier that Rate Roll and Rate Pitch PID values stayed the same during version changes, and assumed other values would do the same. My only excuse - I thought AutoTune took care of the most important parameters and never thought of changing the most relevant parameters for throttle. Live and learn.
After that I got the courage to reinstall 3.2.1, keeping the 3.1.5 parameters. It was getting dark outside, but I sneaked in a short test flight in the garden. The pulsing is back! Again you were spot on - IIRC the default Throttle Accel P/I for 3.1.5 were 0.750/1.500 and for 3.2.1 P/I were lower 0.500/1.000. Throttle Rate P are 6 and 5 respectively. So tomorrow I shall play with the parameteres again - trying to reduce "Throttle Accel" even more, even if THR_ACCEL_P lower than 0.5 is "out of range" according to Mission Planner. I did not get as far as changing the Altitude Hold P parameter (1.000 for both versions) today - how would that affect the behavior?
From reading the logs and graphs, the jagged ThrOut curves are still present in Loiter mode, even after the successful tuning in 3.1.5, so I guess that is normal?
Regards Jan - and thank You!
Would be interesting to see how many people complaining have badly set values. Helped with a case on the ardupilot forum, not had response back on that to see if it helped, but the gains were higher than default.
Hi again!
Bad news from last days tuning 3.2.1. I have played with tens of permutations of ThrottleAccel P&I without satisfaction. Mostly lowering both by the same rate, ie. "P" half the "I" value. The pulsing decreases a little by lowering the gains, but the AltHold is getting worse/unacceptable. Re-balanced props, checked BARO foam protection, and nothing is hanging loose on the frame.
Returned to 3.1.5 and kept default values for 3.2.1 (ThrottleAccel P/I = 0.1500/1.0000) and the the pulsing is gone again and AltHold is OK.
In my case the default values were bad in 3.1.5, also in 3.2.1, even if they were different and lower at the the first installation (0.5000/1.0000). I have looked at my tuning screenshots from my first installation (3.2.1), and they confirm my rates were default - not higher.
I think that my issues may come from my combination of frame, motors, ESCs. Looking forward to try 3.2.1 with new motors (change from 460kv to 620kv) and perhaps different props (from APC 14"x4.7" to 12" carbon fiber). This will bring ThrOut down to around 500 on 3s batteries. I also notice that the OP has a big tricopter with similar issues..
-Jan
There was another listing on this problem and it was the value of ATC_ACCEL_RP_MAX set too low. have set mine to medium 108000 and ATC_RATE_RP_MAX set to 25000.
Apparently the 3.2.1 download has very low values which cause a problem.
Good luck
I don't think those params should affect this problem.
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