This is a work in progress. I've tried to address some fine tuning and performance issues.
Denny R. had made a comment about the inertia of bigger props causing issues. I've added a low pass filter to smooth the positive acceleration of the props to see if we can get at this issue. It may require tuning up Rate_P for a few folks, but I saw little issue in multiple flights.
Crosstrack had a small math error that decreased the resolution of it. I've fixed that and upped the default gains to get better tracking.
Made WP hit radius 1 by default. even 3m is too much for quads. (If you pass a WP you will move on to the next)
The Loiter method is tuned a little better by default, and now uses GPS offsets when flying less than 1.5m/s. Code experimentation will continue on this front. Thanks to Emile and afernan for their help!
A fix in the Z Accel startup was added to get an averaged result.
Added the ability to enter Loiter with Optflow enabled. - still a work in progress, not for everyday use just yet.
This alpha is on GIT now and is for user's who want to test code. As always, you need to use the "relaxpatch" version of Arduino you can find in the downloads section.
Update: We've found and patched some small type bugs in the latest and updated some GPS drivers in the Library. Be sure to pull the latest code and check http://apm.tridgell.net/ for the status of each build run against the SIL sim server.
I pushed a version on to GIT that addresses a number of issues.
- the low speed GPS XY calculations were incorrect and have been fixed
- Nav_Rate I term has been removed in loiter control - it's too easy to get two iterms working out of phase
- A second derivative has been added to Roll and Pitch. I found it removed wobbles nicely - Can be adjusted in the planner as STAB_D with a default of .25 (just enough)
- Smoothing has been applied to the motor commands in a way that really quiets down the alt hold pulsing without much effect on latency
- Yaw now has a dynamic constraint and I've upped the yaw gain.
- The motors output now have an LP filter on them so that the accelerate just a tad slower than the deceleration. This is a test to see if it helps big Octo's and Hexa's
- The Rate_I term is now zero'd for first five seconds after takeoff to keep balance.
- Loiter gains are lightened up a bit
- Nav_Rate_P is lower to remove back and forth sped related hunting in loiter
- Compass is enabled by default
- New I2C Library now included which should solve I2C related lockouts
- optflow is still a work in progress.
This update is based on flights today in a very windy environment.
It occurred to me that we're handling the WP nav I terms incorrectly and I reworked the WP navigation to share the same I terms from the Loiter. Even though they use different error input, etc, they turn out to both deal with wind in the same way. I have not Flown WPs with this new code, but heavily tested it in the sim and It's really rocking in hard wind. Transitions from Loiter flight and Nav flight are very smooth. Please let me know if you have luck.
This is a quick patch based on a bad crash Marco had. My theory was an I term that built up during wind that needed to be reset, but wasn't. It's a corner case but It bit Marco pretty bad. Please re-pull if you have R4 running to go to R5. And please, please be careful. This is alpha code not for general testing, but for development. Don't fly it on anything you would feel bad about crashing.
Update R7:Added an auto-land timer for RTL. If you don't change modes for 20s after the copter arrives at home, it will begin to auto-land. If you have failsafe and no GPS, you will immediately begin auto-landing.
Minor tweaks and cleanup
Made climb rate controller for landing universal for all altitude changes
Updated Loiter controller - Works great in the sim, thanks Afernan.
Yup, just seen. It also seems to be the case that I might have been wasting my time trying to get the code to work on an APM2 board at the moment. Looks like I might be swapping boards around tonight...!
My experience with Stab P = 4.6 on my 3DR is that it's somewhat "sporty". If you are flying in stabilize mode it's nice and responsive, but with some quickly damped oscillation on step inputs from the sticks.
I use 3.6 - the response is slowed noticeably but not seriously - you can still get out of trouble manually if you have to. Even lower is probably OK too.
However, you can see how fast it wanders in Loiter. It's generally a lot slower than the response you'd expect from bad stabilize settings.
Let it fly in Stabilize with your hands off the cyclic control. Does it stay level and just drift with the wind? Bump it with your hand while it's flying - does it return to level smoothly and without undue delay?
I was using an APM1 and now I on an APM2. I didn't notice any change in stability when I changed. If tthe gyro and accel gains are similar this is what you'd expect. There may be some second order effects due to the relative frequency response of APM1 & 2 gyros and accels.
Navigation is a layer above the stability loops, so should be independent of the HW to a large extent.
Phil, thanks for the suggestion. I am keen to get camera stabilisation working, which does not look possible on an APM 2 board until February, so I am probably going to swap my boards over tonight and give 2.2 a go in the morning. If I can get similar performance to that which I obtained at dusk, plus camera stab, I will be a happy man. If not, I will revert to my APM 2, give your suggestion a try, and borrow an FY30A to separately stabilise my camera mount. Cheers, Bill
I'm curious that the PID is so high as default when I read on the forums that most are resetting it from 4.600 to lower around P 3.600 for Stab Roll and Pitch. What variables of the craft should be taken into consideration whether the settings are higher or lower? I would assume weight and power and their ratio relatively?
For example mine is Coaxial X8 and flight weight about 2.3kgs . I calculated max thrust to about 7.5kg with the current motor/prop config so have put the optimum flight weight at about 4kg max.
For higher power to weight ratio is it better to have a lower PID for Pitch and Roll for a medium response?