I've build several DJI crafts, 2 quads and a hex.
I picked up another DJI Quad with the motors, props, ESCs with the intention to try with APM2.5.
So I have it all wired up. Since the DJI ESC do not have a BEC, I added another just to power everything up.
On my first attempt to fly it immediately/violently flipped over to the right.
I did the motor test and say I had swapped front right and back right wires.
Corrected that, and just to be safe redid the auto ESC calibration.
Redid the motor test and everything spun the right way (and yes I have the right props and the APM is pointing the right direction).
But the problem persists. A violent flip over to the right.
Luckly I have not broken any props yet.
Yeah, probably just that - try it on as close to the default PID parameters to start with and make sure that your are in STAB mode when you take off. Good luck!
well, since mine is so stable, if it's not a hardware issue, it has to do with PID tunning. The twitches may also be some ground effect since you flying close to the ground so far and with big propellers for that frame. Try a RATE P of 0.90 , RATE I =0.010 and RATE D = 0.001 to see if you feel any improvement. Also set your STAB P=4.000 and STAB I = 0.0 to test. I'm using 1050kv motors with 10x4.7 props and those are approx my settings. This set tends to have a very high thrust ratio wich may get a bit unstable if you use the default params.
I'll go try those rates out today. During my tests yesterday it
Yesterday I programmed in a flight plan and did some testing in a big field with a couple of batteries.
Right off the bat it continues to be kinda unstable. In fact, at one point while in Stab mode the thing just did a flip. I would have been pretty proud of myself if I had indeed tried for that.
Another time right on take off (2-3 feet up) one motor quit and it fell to the ground. Luckily no damage and it started right up again - so it wasn't a motor/hardware problem.
I did several auto (nav) tests (ensuring GPS lock before take off)
The first time I flipped the switches, it looked like it was trying to find the starting way point but started getting unstable as it slid to the side and dropping altitude rapidly. I flipped back into stab mode, got it back under control and brought it home.
The second test it started flying off as expected. I walked quickly behind to keep. It looks like it got to the second waypoint and was banking for the next (it was almost a straight line from waypoints 1-2-3 but I guess not)... but the distance from me was getting beyond the point of being able to identify orientation visually but I could see that it once again it was banking dangerously to one side. I flipped over to Stab mode and then RTL to at least get it on it's way to me. Regained control and landed uneventfully.
Next I tried altitude hold. Took it up about 50 feet and hit the switch. Nope. Thing just wanted to drop straight down outta the sky. I simply could not get it to work.
I'm planning to do some tweaking today and trying again.
I assume you meant Rate P of .09 and not .9.
.9 was scary to watch it trying to lift off ;-)
So things are progressing nicely. It's not "Naza stable" but it's certainly flyable. I observed some odd waypoint flying characteristics that I thought you all could advice on.
So I set a way point course with about 3 way points. Close enough that I could keep an eye on it, but far enough away I wouldn't be able to discern orientation (short of it moving across my field of view).
After achieving GPS lock, I lifted off and hit the AUTO switch. Off it flew away from me. It reached the first waypoint. It was far enough away that I couldn't determine what exactly it was doing but it stayed in that general area for a bit before turning and flying to the next (across my line of sight).
With this horizontal track I got a good look at what it was doing. It would fly at an increasingly fast speed (you could hear the props loudly chopping through the air) and then right it self with a quick gain of altitude, wobble back, stabilize, then try again by tilting "forward" and continue to fly towards the way point. It would repeat this until it got to the way point.
At the way point there may be some oscillation - hard to tell as it's far enough away and visually I couldn't determine if it had reached the way point or doing another one of those stabilization correction things I described above.
By the time it looking like it had reached the last way paint before it should turn and fly back to me (RTL) it started doing another corrective stabilization thing but it was dropping a lot of altitude and getting to a point low enough that some trees closer to me would block visuals, that I flipped the mode back to STAB and hit the throttle to watch it sky rocket up and right itself.
I then flipped the switch into RTL mode and watched it make it's way back to me. Once it was close I took control and landed it.
I wasn't going to try way point navigation again on this configuration but I wanted to test more RTL and stabilization stuff. I'd take it quite a ways up and kill the throttle. It would of course start tumbling out of the sky, slowly rolling unto it's back. It's hit the throttle and in a loud whirl of the props it would right itself. Very impressive. I did this several times.
Another test I just flew it off in the distance and this hit RTL. It didn't look like it was flying back to me - more like across my field of view - I was getting nervous as it was getting towards some houses so instead of giving it a few more seconds to figure itself out I took control and brought it back.
While doing some simple hover/control tests up high it all of a sudden tumbled out of the sky. It wasn't a gentle tumble like if I just killed the throttle, it started " flipping out".
Crash landed in the grass. Luckily it was very tall grass and there was no visible damage. WHEW!
I did however notice the BEC had one lead come unsoldered from the power lines. This could easily have happened post crash but I don't know. I would have thought it would have just caused the motors to quit resulting in a gentle tumble rather than this violent one - but who knows.
So I plan to get it up in the air - but I was hoping someone could advise on the flight characteristics I described. One setting I had changed before this flight was lowering the way point flight speed from 5 to 4. Perhaps all I have to do is drop this some more? Or is there another setting I can tweak to make simple forward flight more stable - stable to the point where it won't zero the pitch suddenly (causing oscillations)?
I suspect you're right on the solder joint. With all my tumble tests leading up to that - I think I weakened an already iffy joint that I had soldered and it finally gave way. Thank gawd for the grass!
Just have to smooth out the waypoint flying and overall stability.