ok so we bought the thing, we followed the instructions and double-triple checked, it still doesn't work.
the problem is: it is very unstable, it can't stabilize itself. We try to get off the ground , and within one second of take off, it goes insane, makes a sudden move/ flip... without touching anything but the throttle stick.
We tried to hold it in our hands while running, and it gave us a vague impression that it acts as it is in "+" config, although it is in "x". Also, it seems to try to stabilize in the wrong way: instead of compensating, it reacts exactly opposite, and increases errors.
one other issue: when throttle goes to 0, two motors stop fast, the other 2 take about 2 or 3 more seconds to... could that mean anything? Also, when it is almost taking off, but keeps contact barely, it spins... is that just vibrations, or does it mean anything?
I actually wanted to take a video of it but we ran out of propellers and also a motor mount broke. So a video will be coming shortly (if it helps any). We also have some logs, just say if it can help.
(we are begginers to quadcopters and RC in general, but say we know our way around mechanics and electronics and Arduino...we are students!)
thank you very much,
any help is welcome,
"one other issue: when throttle goes to 0, two motors stop fast, the other 2 take about 2 or 3 more seconds to... could that mean anything?"
Yes, I believe this indicates at least one issue: The ESCs are not calibrated, or not calibrated *equally*.
Calibration means that your ESC "learns" the extreme positions of your RC controller throttle stick. Let's say your RC controller puts out a PWM pulse with a min of 1050 and a max of 1850. All the ESCs need to know this, so that they all start (and stop) at 1050 pulse and go to max at 1850.
This may only be one of the problems you are facing, but you will not be able to resolve the others until you fix this.
Success equals: All ESCs start at the exact same time, seem to spin at the same speed and stop at the same time.
imo i would do the individual ecs cal. really works good.
we have calibrated the esc-s both automatically and manually...
could anything be wrong with the motors themselves? Unlikely, right?
now we haven't gone that far...
we thought we should seek help before going into parameter tuning and code modifications...
But isn't the thing suppose to fly "right outta the box"?
No my dear friend :) it would fly out of the box, doesn't mean it flyies WELL out of the box ! Well first of all, check your ESC's manual and see if it has a "brake" option, if it does, it can be on, off or in some cases 3 settings. Choose off or low brake. That could be one of the reasons. Next, calibrate throttle range, following the ESC's manual again. Usually, what you do is connect the ESC with the motor to the RX, turn on the TX, put throttle at max and plug the ESC to the battery, it will beep indicating max throttle position detected, then move the throttle to 0 and it will beep again for low throttle. Do the same to the 4 ESCs. Then, check if your radio is not in HELI mode, because usually HELI mode has mixes active for autorotation compensation. You should have the radio in ACRO mode without any mixes active. Then, you should make sure all the motors are spinning in the right direction and if the props are all well attached. For X config, looking at the rear of the quad, you should have : front right(motor1) = ccw | front left(motor3) = cw | back left(motor2) = ccw | back right(motor4) = cw (where cw=clockwise, ccw=counterclocwise). You should try to describe your quad specs : motor kv, model and brand, battery type, ESCs, etc, and size and weight or a photo so we can help better. You should start with settings low and increase them slowly, like RATE from 0.060 to 0.180 . within this range, the quad will begin to oscillate at some point, at that point, decrease it a bit (0.010 or so). Do this with a low STAB P like 3. After you have it flying without wobbles, go on and read the tunning guide and tune it at your taste. Hope this have helped somehow.
wow, thank you, that is a lot of info
-yes the ESCs have brake, we never thought that could be the problem. We didn't play with that setting so we assume it is default for all ESCs. Will check.
-radio in heli mode. Noted.
the rest are ok. (we will check anyhow)
this is what we have:
(guess it is what they call "standard config")
how does one twist a motor?
"My copter yaws right or left 15° when I take off: Your Motors are not straight or your ESCs are not calibrated. Twist the motors until they are straight. Run the ESC calibration routine."
That part is regarding quads with round tubular arms and motor stands that may come loose and rotate a bit around the arm during a crash.
ok we didn't expect much from the beginning, being unexperienced and so, but doesn't fly WELL doesn't mean doesn't fly at all, right?
I would fix the ESC problem before tuning parameters. The ESCs not starting and stopping at the same time *IS* a problem, regardless of any other problems. You can't tune it with uncalibrated or faulty ESCs.
You might have a bad ESC, perhaps was not programmed correctly at the factory (or just programmed differently that the other ESCs). Most ESCs have a programming mode where you can set the ramp rate, brake feature, etc.
Also, check that the motors are all spinnig freely (I once had one where the motor shaft was a bit misaligned and rubbed against the motor casing. Not only did it not fly well, it made that motor almost red-hot!)
It is hard to troubleshoot a problem in a quad, but the most important advice I have, which probably applies to any tuning of any device is:
- Change only one parameter at a time
- Try to isolate each parameter for testing
- If in doubt, swap out a suspect component with a known good component.
Since you probably don't have any "spares", you might want to redo the wiring and swap one of the suspect ESCs for one of the good ones. Then see if the problem "follows" the suspect ESC or "stays" in which case it is something else.
Actually, some of the motors do seem a bit more "sluggish" when turned with the hand. Of course, we can't really say if it is so. It is just a tad. Any scientific way to test?