Version 2.5 of the ArduCopter code is now available in the AP Mission Planner and in the downloads area!
The default PIDs are optimized for a 3DR/Jdrones quad with 850 motors and 10" props. If you're using more powerful motors/props, start by turning down Rate Roll P in 25% steps.
While some testers have reported very good flights with the default PIDs, some have reported that this release is a little "sharper" due to the DCM improvements and have found they needed to:
reduce stabilize P by 10% (i.e. 4.5 -> 4.2)
reduce stabilize D by 30% (i.e. 0.15 -> 0.10)
increase rate D from 0 to 0.001
Tuning loiter can be tricky. Refer to the discussions which will appear below for more community feedback on what parameters work best.
Please post your feedback in this discussion. For enhancement requests and bug report, please add them to the arducopter issues list. When possible please include logs (tlog and/or dataflash) and tell us whether you're using APM1 or APM2 and what version of the software you're using (presumably 2.5 but tell us anyway!).
Thanks for this release go to the developers (both in the core team but also those who have provided bug fixes through the issues list) and also the community members who participated in the previous release thread and provided some great detailed information in the form of issue reports and logs which allowed us to nail some bugs!
I would never fly this way in acro / manual mode, but in Stabilize mode it is great. I also saw more issues uncovered, air causing vibtations. Again this was for slower Photography flying.
Ok, here is another problem Ive spotted in the mind field of hardware issues and for people who continually bang their heads trying to fix them through PID tuning. .
If you have a housing that is covering over all of your electronics such as a plastic container,.. then when you descend or ascend quickly the pressure inside the container changes and gives your barometer an false reading.
For example if you descend quickly the pressure increases inside the container making the barometer think that you are descending faster than you actually are. So the APM will try to compensate this out and try to increase the throttle and this probably cause a bouncing behavior some people are finding happens .
Some may argue that the barometer cant be this sensitive, but I beg to differ because the pressure variation it can sense for the pressure variances in altitude that it works off is very fine. The pressure change inside the container even for horizontal flight will be enough to for it to sense the changes of pressure in the container.
This also includes pressure zones around the incoming and out going air stream around the props if they are to close to the container or even if you have an open center frame the pressure zone around the props can possibly still affect the barometer
Im considering some fixes for this such as a tube that has a H tube branch at its end and that sits above or below the center board.
I would be interested to know what others view and ideas are on this. .
Ive opened a separate discussion on this here http://diydrones.com/forum/topics/barometer-issues-and-pid-tuning
I found the same issue about six months ago. I use a clear plastic light post dome that I cut in half for my Quads. I have since drilled 1/2 inch holes around the top of the dome. This allows air to vacate when decending and to allow pressure equalization on rapid assents. Here is a picture:
There are six 1/2" holes around the top. Sorry, they are hard to see in this photo. This works really well and since the dome is cosmetic only (I don't fly in the rain) it actually looks good with the holes.
Looks nice Allen. I only have the cover to protect the electronics when i crash. I started a post on the below link and have some ideas about testing and reducing the pressure anomalies. Nice to know then what I suspected has happens to others as well and something to keep an eye on when we see strange behavior
I had try ttuning Loiter in 2.6 beta, still no luck, the quad will stay for about 5 seconds after that it will fly away for upto 25 meter before I stop the movement by taking the control back. My quad using X525 frame with NTM motor 2836/750 KV. Stability mode fly perfectlly stable and no issue with compass.
I wish someone can help me analyze my log and give me some hint on which parameter I should tune. I have enable PID logging, and in these flight I use Chanel 6 tuning to tune LOITER_P values, min = 0 to max 1500.
I had 2 flights and both of them no success in Loiter.
Thanks for the logs. You were tuning the loiter speed which controls how quickly the copter wants to get back to the target. What's more important is to tune the loiter rate which controls how much the copter leans to achieve a given speed. You can see this in the pic below which is the latest mission planner. Your loiter rate's P value is 0.6 but the default is 2.0. It looks like it needs to be quite a bit higher than 0.6 so maybe try tuning it starting with a value around 2.0.
The reason I think 0.6 is too low is that although we don't have the exact output from the inner loiter rate controller, the NTUN (navigation tuning) message has two column, "nav lon I" and "nav lat I" which show the "I" term on this inner controller. In the pic below you can see this I term keeps climbing and eventually builds up enough to bring the copter back but it takes a while. Much better to increase the P term.
In the pic below, red and green lines are how far the lat and lon are from the target. The blue and white lines show the I term build-up on the loiter rate controller.
Hope this is clear-ish.
I appreciate this explanation. I'm in the same boat as far as nailing down the tuning, so this helps me as well. What do you think we should expect if we instead tune the loiter Rate P value too High? Would it lean heavily and rapidly overshoot back and forth across the target location?
Also, do you have a suggested starting value for a standard 3DR quad with 880kv and 12x4.5 props?
Thanks for the help!
Yes, if the Loiter Rate P is too high it will lean too much. I've never tried cranking it up far too high but I guess it would lean too far forward and then too far back back repeatedly as it approaches the target. And then once it gets there it would have a hard time staying there.
There are probably many ways to get overshoot but one way that you will get that is if your Loiter Rate P is too low. What happens in this case is that the I term builds up as you're approaching the target but then because the I term reacts slowly, it will stay high as you sail past the target.
I just went back from another test, this time I tune LOITER_RATE_I using CH 6.
The result, copter stays within 10 meters box, I'm not satisfy yet.
As a brief, bellow are some values on the parameter (Full parameter attached):
LOITER_RATE_P = 2.68
LOITER_RATE_I = 0.010 (This is my starting point, CH6 configure to tune this from 0 to 1.000)
I've tried to analyzed my logs and according to my understanding my LOITER_RATE_P is too high.
I will try another test tomorrow, my plan for tomorrow is:
I'm gonna set LOITER_RATE_I to 0.2 and I will use CH6 to tune LOITER_RATE_P.
If you have other suggestion please let me know.
I'm really appreciate all your input.
I think you're right actually, I think your loiter-rate P is a bit too high. The little jagged edges in the P component (green line) are quite visible and of course this carries through to the output (white). I know I'm going back on my previous advice a bit but I think you need to reduce both the loiter rate P and maybe the Loiter Speed a bit.
As a side point, at some point I'd like to try testing the output of our controller at various speeds. So for example, set up a case where it tries to maintain various speeds one after the other (i.e. 0.5m/s, 1m/s, 1.5m/s, 2m/s) so we can get a better idea of how good it is in varying situations.
Here is another test, this time I reduce the LOITER_SPEED to 0.4 and LOITER_Rate_P to 1.9 and play with RATE_I, still not satisfy, I guess this time my Rate_P is too low and somehow when error reached 0, the I still too high and it make oscilation.
It is so dificult as I don;t have telemetry nor laptop to tune the parameter. I guess I need to find a way to power up my laptop on the field (The battery has been damaged).
I think I like LOITER_SPEED 0.4 as it seems the quad is more faster in correcting the error.
As usual, inputs are highly appreciated.
What is the unit of 'Loiter speed' in mission planner? The wiki doesn't seem to mention this in the tuning section.
I'm asking this because I had some succes at tuning loiter in low wind conditions, but so far have come nowhere in windy situations.