Replies to This Discussion

Permalink Reply by Rui Manuel Cravo Marques on April 11, 2012 at 5:48am

Hi Randy. Don't you think the 2 lines never getting together may be the lag between radio input and apm response ?

Also having some strage behaviours with power losses and flip overs, I decided to test the rc_speed. I confirm that at 490, even if the motors behave smoother, I have drops of power, wich I think may be due to loss of sync from the ESCs. At 200, the quad gets a bit harder to control but I don't have those power glitches. The flip over I had when switching to loiter, I think I had it at 500. So, my ESCs may not be able to handle those frequencies even if they arm ok and are able to respond most of the time. Do you think this may be correct ?

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DeveloperPermalink Reply by Randy on April 11, 2012 at 5:45pm

Rui,

     The lines coming together (which means the APM is never successfully getting to the pitch you're inputting) are unlikely to be caused by a lag between the radio input and the apm response.  It goes on for far too long and the gap is always on the same side so it appears the APM is never able to get the quad to the desired pitch, it keeps falling short (as opposed to overshooting which results in a wobble).

     Good move on testing the ESCs frequencies..sounds very possible that the ESCs can't keep up.  There's a lot of room between 490 and 200..so I guess just going down until it gets more reliable would be good.

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Permalink Reply by Jonathan M on April 11, 2012 at 1:57pm

Interesting,  I have seen this before on my quad, and I don't use an Stab_I terms.  I don't have a sound argument, but I remember reading that to not use Stab_I if using the PIDT1 control scheme, which i believe is what we use still.  Is that a correct assumption?

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Permalink Reply by Jason Tinacci on April 10, 2012 at 5:43pm

Hoping to get some help...

I tuned my quad (3DR 850kv 10x4.5 3300mah lipo, APM1, 2.5.3) to try to get rid of the unstable loiter. After changing the default PIDs:

Stab P from 4.5 to 4.4;
Stab D from .15 to .10 and
Rate D from 0 to .001

Params attached.

Loiter seemed to work fine, hovering around 15' but it would drift to the left. Then after several seconds it took it self for a walk forward. See video.

What can I try to have it sit still?

http://youtu.be/KRMYLQP2MdU

Attachments:

• 2012-04-08 06-10-41.tlog, 540 KB

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Permalink Reply by Eric Tweet on April 10, 2012 at 6:04pm

I'm afraid I don't have any suggestions, but rest assured that you're not alone. Mine does the same thing, loitering for a short time then going off to play somewhere else on its own! I'm patiently waiting for any word on what to do to get things working properly. Meanwhile I'm spending most of my time CH6 tuning the HLD and LOITER P values as a start...

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DeveloperPermalink Reply by Randy on April 11, 2012 at 5:51pm

the next version 2.6 has more logging of the loiter values so hopefully that will help people tune it better.  What you'll be able to do is go into the terminal screen of the mission planner, type "logs" then "enable PID".  Then when you're tuning using channel 6 it will dump the error, P, I, D and output values to the dataflash log.  Hopefully this will help a bit in that you'll be able to see the individual contributions of P,I and D parts of the PID controllers.

 

This extra logging will also be in the roll, pitch and yaw rate controllers.

 

One thing that's also confusing about tuning loiter is that the LOITER_RATE parameters are only visible in the left pane of the mission planner's configuration screen.  These rate parameters are key to controlling the conversion of desired speed to lean angle so we will likely move them to somewhere more visible on that configuration screen.

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Permalink Reply by Jaan Kronberg on April 11, 2012 at 1:57pm

hey,

may i disable compass in 2.5? with older board i remember it was explicitly said that if compass is disabled i should unplug gps - but it's not that easy with purple board, where both compass and gps seem to be soldered to the board..

thanks,
jk

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DeveloperPermalink Reply by Randy on April 11, 2012 at 5:54pm

Jaan,

     You can disable it through the mission planner:

            1. click on firmware button in the mission planner

            2. click on the apm setup button at the bottom

            3. go to the hardware tab and uncheck magnetometer (or maybe it's called compass).

     Hmm..I wonder why you'd want to turn off the compass if you dsiabled the GPS.  Certainly the GPS is not useful without a compass...but if you're not doing loiter or RTL, I don't think it matters if both are left on.  They don't really negatively effect performance as far as I know.

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Permalink Reply by Jaan Kronberg on April 12, 2012 at 9:55am

hey randy,

tried some flying with compass disabled and it seems that it's holding yaw better without compass.. not sure why :(

is there anything broken with camera stab in latest versions? with roll servo attached bird rotated like mad.. had same issue with 2 different boards - on older one i thought it might be consequences of crash (some sensor dead or whatever), but today i had exactly the same issue with octa and purple bird.. and pitch servo is wobbling strangely... something very fishy :S :( let's put it that way - camera stab is either working in some new and mysterious way, or something is broken :)

attaching log files (all of them, one of the first one should be the "rotating" one..)

would be great if you could take a look...

Attachments:

• logs.zip, 662 KB

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Permalink Reply by Patricio on April 11, 2012 at 5:48pm

I had a crash last week testing 2.5.3 with a similar behaivior that some people reported. Quad leaning to its back.

an initial take of was attempted at 40-45% and i could land it. on the 55-59% i had the crash where i broke one propeller and end of the game.

here you have the log.

 

 

Attachments:

• 2012-04-01 09-11-48.tlog, 877 KB

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DeveloperPermalink Reply by Randy on April 13, 2012 at 7:25am

Patricio,

     I had a look at your quad, it doesn't look like you get very far off the ground before the crash.  If you look at the status tab in the bottom right of the mission planner, you can see ch4_out (back) goes to 1920 while ch3_out (front) is down at 1200 and ch1 and ch2 are down at 1460.

     To be honest, i'm a little surprised you can get one engine to full like that while the others are just barely on.  Are you using standard PIDs?

-Randy

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Permalink Reply by Nick on April 11, 2012 at 9:39pm

Anyone else notice in the APM, that flight-modes don't change when switched to? 

Just constantly shows Stabliize.

 

yet in the Radio setup, it correctly selects the right flight mode.

Even in CLI it shows them correctly.

 

But Flight-Data section and even the STATUS tab, just shows Stablize and nothing more.

 

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