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.
Thanx to all: Jason, Marco and JLN
I tried everything. Erased the EEPROM, factory reset, erase EEPROM again... still nothing. Then I remembered to erase the logs too. I can't remember what happened after that, I was getting tired and was still futzing around with my rotor head setup.
I don't know. I was trying to use it as a tool to help solve a setup problem. I think after erasing the logs, it either still wasn't working, or I didn't get back to have a second look. All I know was at some point I figured out the setup problem I was having another way and worked on that for the rest of the night and stopped worrying about those servo outputs. At no point did I see it working.
ArduCopter v2.1.1 R6 test in HIL mode on X-Plane v9.70
LOITER mode test flight with a crosswind of 10 Kts from the right.
HIL test on Aerosim-RC with 2.1.1. r6
All worked very well. Found no issues at all
Loiter is better than ever. Cheched with no wind, medium and hard wind with same pids (Loiter_P = 0.4, Loiter_I= 0.01)
In all cases reached the WP_error=0 (error<1m) (with hard wind it takes some time).
To say something, and to get the perfection, I´m still miss some small damping factor. There is allways an small swinging effect that I think that could be easily damped. Below is the case with hard wind (pitching to it). See the sinusoidal pitch control.Well, I never get tired to say: thanks Jason.
Try adjusting STAB_D in the parameters. Increase that to reduce the swinging.
Let me know how it goes.
I´ve notice that the oscillations of previous image was due to the perturbation on top of the strong wing. Reducing that, it really keeps smooth. I´ve increased a bit STAB_D =0.3 and used following params (best I´ve found for HIL)
LOITER P,D = 0.4, 0.01
Nav WP = 8.0, 0.01
Below is a pulse in roll and then in pitch having the copter in front to the 20knt wind. It´s really quick damped.
The copter flew great today with pre 25th Dec 2011 build. The props have been changed to a 1 inch wider diameter with the same pitch. I figured the Stab gains have to be lowered. There is a subtle wobble it does at times and decided it was due to too much gain. It was lowered to 1.700 and still wobbled at times. What is amazing is the discovery on how well it deals with gusts of wind. I can only conclude is that the direction motions are somehow sampling the crosswinds. Neat build.
Ok, I just checked. Nope, not working.