Developer

Arducopter 2.1.1 alpha

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.

Update r3:

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.

Update R4:

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.

Update R5:

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. 

Jason

Update R6:

Includes fix for Acro mode reset bug.
I went through all of the global variables and gave them lengthy descriptions. It's worth a read if you want to learn more how the internals work. I'll be doing some more organization like this as we move forward with an architectural redesign for 3.0 \
This version is mostly clean-up, but does include 1 interesting performance enhancement. It's disabled by default because It's fairly untested. The idea is that the wind compensation created by the Iterms for lat and lon in Loiter and Navigation are carried over into Stabilize. This unifies all of the modes so that when you switch modes, you don't get a small, but fast change in pitch or roll. This is only noticeable in high wind environment. 
To get this to work, I look for near zero velocity and start moving the pitch and roll into the wind control items. This takes a  transformation from copter frame to world frame, but the result is the copter will hold the position against the wind with the sticks in the center of the controller. If you fly around the wind compensation will bleed off slowly - about 30 seconds.
Again, this is off by default and needs significant testing, preferably in the HIL sim first.JNL has already started and flown this version for real.
The feature may be off by default for another version or two, but just letting you know it's there.
I think it will go a long way to making the mode changes feel seamless.

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.
Failsafe RTL now goes 10M up as it RTLs to avoid obstructions.
Added SIL test for failsafe. 

Update R8:

Minor tweaks and cleanup

Update R9:

Made climb rate controller for landing universal for all altitude changes

Update R10:

Updated Loiter controller - Works great in the sim, thanks Afernan.

Thanks,

Jason

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Replies

  • 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?

  • Real Flight test with 2.1.1r10

    No wind
    Small custom quad 650gr rtf

    Loiter:
    good behavior in general. I' ve needed to low Loiter_P to 1.5 and Loiter_I to 0.01. Higher values produce oscillation not damped. I need more D factor for this small copter: to be tested.

    Autoland. Still the problem of final cut down. Stays kissing the ground without landing. I do propose the R7 approach.

    Simple mode does not work properly

    Angel
  • More observations on flying 2.1.1r10, stock 3DR quad, APM 2.0 board.

    Finally, getting much closer. Some fortuitous advice from DaveyWaveyBunsenBurner led me to dramatically reduce the Loiter P setting (even though his experience turned out to be with an APM 1 board) and that set me on the right track. It seems to me that a sweet spot is around Loiter P=0.86, I=0.005, but I still had quite a lot of altitude variation - one Loiter track had quite dramatic 2-3m bounces. Marco Robustini then advised me to adjust the Stab/Rate PIDs. Close to sunset, in very low/no wind, I flew a few times with the Stab Roll/Pitch down to 4 and I down to 0.03 (pure guesswork on my part). Due to not having time to setup my laptop etc, I did no more configuration than that, but just flew it for 3 batteries. It seemed a lot smoother, especially in altitude, and I am now getting a reasonably good loiter performance. Attached is a .kmz of a track that was between 5 and 6 minutes worth, where most of the track is within a 6x7m box with an altitude variation of less than 1m.

    The great news is that I am now getting a reasonable and repeatable Loiter performance in low/no wind. I say reasonable, because I simply don't know what the art of the possible is for a 3DR/APM2 combination. The bad news is that there are now more variables to worry about when trying to achieve that perfection, and I have no idea as to what the interactions are between all of them. My nightmare scenario would be to have to revisit all the parameters every time I find a sweet spot with one combination. Any advice or guidance from the development team would be most welcome.

    My PID settings below for anybody else with an APM 2 board/3DR or similar:

    3692334114?profile=originalCheers, Bill

    2012-01-13 05-21 31.kmz

  • More observations on flying 2.1.1r10, stock 3DR, APM 2 board.

    RTL now works for me, I think that I must not have been giving it enough time to respond before. In 2.1.0 Alpha I normally get a violent response, in r10 it is really quite slow to start moving back. I have not been brave enough to test the Auto Land for real yet.

    Camera stabilisation is definitely still not working. On other discussions, it appeared that I may have been plugging the servos into the wrong output channels, but it looks like it is a problem with the board, reported on the other discussion.

    More seriously, I still cannot get Loiter to work. In low or no winds at the moment, I am still getting big circles and occasionally violent pitch changes when flicking flight modes. I am using a Loiter P of around 2 (fiddling makes little difference), and tried Marco Robustini's suggestions of I as 0.020, but whatever I do I still get big circles even if I make I zero. Altitude Hold does not look as good as 2.1.0 Alpha. If this release is about to go to Mission Planner, then surely someone somewhere is flying this successfully, in different wind conditions with tuned PIDs for a stock 3DR with an APM 2 board. If they are, then please could they promulgate those PIDs. At the moment, I just feel as if I am chasing my tail. I know Loiter can work very well as it has happened for me on the odd occasion, but right now it is not repeatable.

  • Developer

    ArduCopter V2.2 (not alpha) on GIT for tester/reckless... in the evening my video of the flight tests.

    EDIT: tested with AeroSim and is unflyable (dunno in the reality, I do not risk), there's big
    obvious bug in the alt_hold control, don't fly at the moment in the reality with this release, see video.

    I make a premise: could be just my problem, but for safety we believe, I await confirmation by JL or Angel, like me who use assiduously the sim for test new release.
    Using the default parameters the quad
    going up and down violently in Loiter/RTL/Auto with the throttle stick at the center, if significantly lowering the "Throttle Rate P" (0,1) and "Altitude_Hold P" (0,050) i've very little improvement, but the bug is already present.
    I think the problem is here, in the calc of "rate D term", line 190:

    http://code.google.com/p/ardupilot-mega/source/detail?r=3c3bfcdf0ec...

    rate_d = ((rate_d + climb_rate)>>1) * 1; // replace with gain

    I've replace "* 1" with "* .1" and now work fine, but dunno if is correct.
    RTL here doesn't work, the quad surpass the Home point and doesn't try to return, autoland in away location.
    With autolanding same problem, but now the jump is too low, need to try in reality.
    Please Jason if you possible in the future check first with AeroSim at least where you change the code before put on GIT, many users here use the GIT version without first simulate and this can be risky.
    Two way: closing the GIT who is out of the dev/tester list, or better control in the sim before release it, I agree that it is at the risk of the user, but prevention is better than cure (IMHO).



  • I did a methodical test in my basement to track down the source of the sonar noise.  It does NOT appear to be electrical. (And just to clarify for everybody, I have the RC filter, shielded wire and heat on my sonar already, and when I flew last the log show absolutely terrible noise on my sonar.  This is on a big trad-heli.)

    So, first I ran the APM, and only the APM. Xbee, and GPS were on. Servo switching BEC was off.  Did a test in my basement holding the heli with the tail vertical so I could shoot the sonar beam down the basement to get a reading that was long, then swung it down to shoot the floor, back up to shoot long, etc. a couple times.
    Sonar was clean.
    Then I turned on the servo BEC and servos.
    Clean.
    Then I pulled the motor pinion and tried it with the ESC plugged in and the motor turning free.
    Clean.
    So, I put the pinion back in.  Removed the tail blades and the upper section of the head.  So all the gears, the tail shaft and grip, and main shaft were all spinning.  There was very little vibration like this.  Very little load on the motor/esc also.
    Clean.  Nothing.  Check out the attached graph.
    At this point, I figure it has to be either accoustic or vibrational, as I originally thought.  The only potential for electrical noise at this point is possible if the load of the main blades causes the amps to spike up enough to make more EMF?  And BTW, it would HAVE to be EMF, as the motor battery and ESC are COMPLETELY seperate from the APM, the ESC is opto isolated in fact.
    I'll run a quick test again with my cap bank plugged in.  It wasn't.  I guess there's a small chance the large bank is inductively picking up EMF from the motor.  I've heard that's a problem with cap banks.  
    If it turns out to be accoustic or vibration, I think this could be significant in proving that some people who persistently have problems with alt_hold, is because their vibes are too heavy.

    Sonar_quiet_1.JPG

    https://storage.ning.com/topology/rest/1.0/file/get/3692334248?profile=original
  • 2.1.1.r10 HIL test on AeroSim

    LOITER simply perfect, even better with wind.

    AUTOLAND worked for me, including disarming at the end.

    SIMPLE mode NOT worked well (nor in r9): tested in HIL and REAL. See what the controls do...

    3692333807?profile=originalIf the real flight confirms the loiter for me as for Marco, we are really close to the end (of this step)

    Thanx Jason.

    Angel

  • Could I get some guidance on the attached log file please?

    I'm running r10 but loiter keeps "stirring" into a big circle. I had this with R6 too but 2.0.50 was a good loiter.

    I have recalibrated everything several times, checked motor alignment etc. Is there something else I can try?

    The attached log is quite short, I will try to get a better example tomorrow.

    Thanks

    D

    2012-01-12 07-44 5.log

  • brrrrr..

    can´t load r10 code. After "Done uploading" with Arduino (as usual) it remains beeping long time with leds off. I´ve repeated many times the process and nothing (done with r9 and work well).

    anyone has this problem?

    Angel

  • Developer

    FLIGHT TEST WITH ARDUCOPTER 2.1.1R10 - LOITER AND AUTOLANGING (APM 1.4)


    This is the video of my first flight attempt with ArduCopter 2.1.1R10 and my new little quad.
    I struggled to find a good setup of the PID, and still have excessive wobbling during descents, i tried in every way, especially by acting on STAB / RATE P&R "I" but to no avail, always wobbling.
    Is a problem related to an excessive drop in the rpm engine in Stabilize, taking it a little more gas during the descent the effect is greatly reduced, obviously.
    I think you should turn off the engine at zero throttle but have a much higher rpm of around 5<->30 % of the throttle excursion in Stabilize, like in Loiter mode but more aggressive for better and fastest control in fly.
    Anyway about loiter I can say: please Jason, now don't touch the loiter code, thank you! :P
    Is almost perfect in zero wind, max 2 meters of drift at worst, only 1 meter on average... nice work guy, thanks to Mr Afernan for porting the code from ArduPirates NG, and to Mr Jason for having improved!
    We await the report of who has tried it with wind, but usually works better because the corrections are almost always given in one direction, avoiding the circle effect.
    About autolanding: mmmm... the same bad results I had with AeroSim, identical, the same behavior... the quad kissing the ground then drift and jump, like if the loiter control after the first ground touch is totally disabled.
    Even when the quad hits the ground loiter function should remain active (I do not think so, it would move that way), of course, the engines will drop further regime to avoid those jumps.

    Strangely
    Jean-Louis with X-Plane does not have this problems, at this point I think is better AeroSim as realism to test this type of functions... now when i land correctly in AeroSim i try again in the reality! :-)
    I have recently read that there's problem with the sonar in the latest alpha, saying that, look at the video and judge yourself, mine is perfectl!

    Good vision...

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