First flight... it's drifting!

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1

Hey all… Got my Iris out for it’s maiden voyage today. Let’s just say I sucked at the controls. I’m glad it made it home, actually.

I was thinking first flight, take it up maybe 5 feet, and just let it hover and mess around with spatial controls and yaw. NOPE. It is kind of hard to control, mostly because it was drifting rearwards quite a bit. Maybe about 1m/s. Enough to throw me for a loop. It also descends a bit when it drifts/pitches. It actually hit the ground and flipped. Not bad for my first time, eh? It was only 5 feet off the ground though, and came down kind of slow. I think a leg caught on the ground.

Oh well, no biggie as I soon find out.

Next flight up - It is hovering around 4 feet and descending again, and pitching rearward. So I jam the altitude up a bit and it just took off. Crap!! So now it’s maybe 60 feet in the air… then… it is in front of the Sun… CAN’T SEE CAN’T SEE!!! CRAAAAAPPP!! Then it goes over my house to my front yard area (I’m on the side yard)… Me = freaking out… I calm down and control it back towards me. It’s facing wrong way but I get the yaw right… It’s descending now and moving maybe 4m/s towards me. I manage to get it down but it comes in quick, and when it lands it flips over.

Oh well, fortunately it’s still OK. I knock some dead grass off it, and secure the battery door.

Third trip up. Only about 2 feet again and I see it drifting/pitching rearward. So I shut it down. Disarm. Turn on safety mode. Pull the battery, etc…

So now I need to figure out why it’s pitching like that…

Is it my Transmitter? Do I need to trim the pitch some?

Or is it a parameter?

Or is it a prop issue? One of them looks like it might be .1mm (width of a hair?) above the motor mount plate, but it’s nice and snug. None of the props slip when I tug on them and hold the motor in place.

Or something else?? Wind?? It was pretty windy, admittedly…

Wind + Backyard smaller than I thought I would need + me being a noob = just relieved it’s back on the ground in one piece… :smiley:

I also forgot to check all my failsafes (e.g. tx off) and I think I only got GPS lock once and not on that time it shot way up into the air… omg, really scary, that was… :open_mouth:

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what mode are you flying in? for me that sounds as you’re flying in stabilize and are expecting the behavior of loiter mode.

copter.ardupilot.com/wiki/flight-modes/

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Yes, I was in STB stabilize (since the instructions are so adamant about learning that mode FIRST)… I knew loiter would fix it, but I was trying to get the hang of it using STB.

So are you saying in STB mode when it drifts one direction, it’s supposed to do that?? I expected it to mostly hover in one place, given I was giving it no TX inputs. I realize it wasn’t Loitering but I expected if I don’t give it pitch or roll it would stay in the same spot… Should I trim my TX so it stays mostly level and in place??

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so actually stabilize mode is not position or altitude hold. it stabilizes the attitude of the copter for roll, pitch an yaw. in short it only holds heading and level, not position, not altitude. in stabilize altitude is controlled manually by throttle, that means it will always go up and down you need to permanently make fine throttle changes to hold it on the same altitude. in theory it would stay on the same horizontal spot, but even the smallest amount of wind will drift it away. if it accelerates and drift away faster in stabilize this is mostly caused by a bad accel-sensor calibration. you need to teach the APM what level is (level means when all the motors seen as one plane are level (bubble level). possibly the 3DR copter come perfectly level calibrated, but I doubt that. did you do the calibration of accels via the APM planner / mission planner?

it is important to understand that stabilize mode is the base for any other mode. if that doesn’t work you won’t have a working loiter, auto, etc.

i suggest that you get stabilize working, then alt hold and then go over to loiter. when you have stabilize working so that it hovers with minimal stick inputs you can switch to alt hold, at this point the copter will hold the altitude when your throttle stick is in center position but you still need to hold position via sticks.

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Hi Fletch

it was drifting rearwards quite a bit. Maybe about 1m/s. Enough to throw me for a loop. It also descends a bit when it drifts/pitches. It actually hit the ground and flipped. Not bad for my first time, e

Stabilize is just that. Stabilize. The autopilot is just taking in your stick inputs and sending them to the vehicle. When it moves you need to change the stick inputs to keep it stationary and not climbing or descending.

You can try Alt hold where you control the horizontal and the autopilot controls the vertical and Loiter where you control the vertical and the autopilot controls the horizontal.

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OK I guess I thought even in STB mode it would basically just sit there. It probably isn’t perfectly level, like ziisco said - so I will try that, where can I read about how to do that?? I can’t find it on the wiki here…

Thanks all, and thanks Craig. I think I get it now, just a mis-understanding on my part I suppose. I do want to learn it in STB mode first, I specifically did not use LTR or ALT because I want to learn STB first and get a real good feel for how it handles.

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Its all in the manual. Start off in a big field in ALT mode until you get the hang of it then move to STB, only way to go.

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I’ve read the manual, like three times. There’s nothing about acceleration sensor calibration. Other calibrations, yes.

Yeah I might have to start with ALT or LTR just to get the hang of STB, or at least until I get my trims set properly. I kept telling myself don’t let it get more than like 5 ft off the ground and play with it in STB… well you see (above post) where that (almost) got me… almost ended up with a fly away basically… scary stuff… :smiley:

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if you use apm planner 2 there is a button accel calibration under inital setup tab. there is similar button in mission planner too, but I don’t use that as im on Mac. but it’s mainly just click that button and follow the instruction about how to place the quad and some OK-clicks.

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Ok so I re-calibrated my accell sensor I guess? I had to lay it on a flat surface, then flip it up on its side, then other side, then front, back, and finally flip it over. How can I review these changes, what are the params? What are the defaults? Just want to make sure no strange readings got stored in there accidentally. My laying it on its side is not exactly scientific, but I think I got it right. :slight_smile:

BTW regarding my Trims on my TX, do I need to re-calbirate? I went into Mission Planner and to Radio Calibration and it looks like some of my trims are not perfectly centered along the configured range. So I did some math and re-centered them better. But I’m not sure this was the right thing to do, so I actually undid my changes. Thoughts??

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as far as I know, DO NOT play with the trims on the radio. just keep everything clean on the radio side and run the calibrate radio function. the board will read the max,min and mid values and save accordingly.

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It would be nice if others could chime in as well? Thanks blackbloy - I do tend to agree, since trims get knocked or reset more easily (more easily than firmware tweaks) which could be detrimental and also trims give me instant tuning, firmware doesn’t, so you want trims to be in the middle ideally…

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No problem sir.

hope you get it flying nice as soon as possible.

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Was going to wait for a nice non-windy day, but it’s been Ides of March every single day now. :smiley: I am just trying to narrow it down to a drift, and the wind doesn’t help me troubleshoot. I think I will try LTR and see if it holds its own heading ok. Cam I then look at LTR logs and see which motors were working hardest at what times?

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I think you can.

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