Hello Everybody,
i have done a APM 2.0 flight test today, unfortunately, during two tests, the copter flipped over without even lifting off. - Even the video is quite funny, i would like to find out what may be wrong and fix it.
Here is the video link:
Anyone got an idea what may be wrong here ?
Also, does anyone have an Idea on the PID parameters ?
The Copter is 1,1 x 1,1 m and weight is ~ 15 kg. - Props are 11x7 - 3Blades and Engines are 420 kV, 850W. Battery is 8S, 35000 mAh.
Cheers
Florian
Replies
Can you post the screenshot of the gyro graphs, either in static or when you flipping IMU?
I wonder if anyone makes a controller that can run 16 motors so that we can build Octor16 heavy lift craft with cheaper motors, and smaller props.
Florian, your actual rpm, under load with the 14" prop is not going be any were close to the theoretical rpm of the motor under no load. But, you're going to have to do some testing to find the right props. There's not going to be a turnkey solution. You are really pushing the bleeding edge with such a heavy lift copter. You'll be an expert teaching us, after you finally get this bird flying.
The hardest part of building such a copter is gong to be finding the props. You almost have to build your copter around the props you can find.
A lot of people using Graupner brand props, but I have no experience with them myself.
Here's link to a site that sells Graupner props:
http://www.rchobbyhelicopter.com/store52/agora.cgi?product=UAV_Quad...
They have 13" ones.
Also rctimer.com is a good source for carbon reinforce EPP props. As well they have these 16" props which come in CW+CCW matched sets that made for multicopters::
Florian, I still think you can get it flying with your current configuration with some PID adjustment, but you'll have an easier time with the larger props and batteries.
Hi Florian, try to hover your octo in Acro mode with "ACRO_P" to "3.5", but not fly, just a little hover al 20 cm from the ground. for check all motors/props direction... if you lift without going to flip everything is ok, but don't fly in acro!
If the wiring is correct is likely that you correct attitude (in Stabilize) during takeoff before quad come off the ground, and this is absolutely dangerous.
The takeoff wants dry and firm, using only throttle.
Put your "STAB_I" and "STAB_D" to zero an try with "RATE_I" to "0.01".
The best way to do is to use the pid tunning of CH6 in flight, all my pid have been accomplished with this system, , but this requires a lot of experience and coolness during flight, and obviously the quad's at least off the floor... :P
Another trick: double check the CG, your "picnic flying table" (recalls that but i like it, LOL) seems to have too much weight on the base and just below, this makes it very sensitive to the flip.
About your battery: 8S, 35000 mAh???????? ARE YOU SURE???? ;-)))
As mentioned in another discussion by Mark Zimmerman, please download and post your logs. It would help to see what's going on. In you case, I think you've basically got the engines running too high an RPM, with the 8S battery, and such high pitch props.
Ok, reviewing this again.
@Florian
Once you've verified items on my list, try this. I just noticed that you are using 8S and 11.x7 props on a 420KV motor. That's a lot of pitch for a multirotor craft. I have a feeling that each motor is generating too much thrust for the software to handle with the default PID values. Why don't you try dialing all the stab P values a bit. Maybe start with 4.0. Also, have you balanced your props?
@Michael
The fact that you are getting random flips could be from unbalanced props.
Florian, I'm in the Dev Team too, and quite familiar with the code. Basically, with the PID settings you have, the craft should not be flipping. As Adam says, many people already run Octo, the code works fine.
Things that can cause your flipping behaviour are:
1- The APM is oriented incorrectly relative to the motors. This means that the APM keeps asking the motors to correct its orientation, but due to the motors being in the wrong place instead of keeping it stable, it ends up flipping it.
2-Your motors are configured for Octo X, but you have not set your frame configuration to be X, in Mission Planner or vice versa..
3- Your trims are not centred, and your roll or pitch is offset to the side that you are flipping.
4- Your ESCs have not been calibrated properly, and motors on one side spin faster than another.
5- Your radio has not been calibrated properly in Mission Planner.
You need to check that any one or more of those things in the list is not a problem before you attempt to lift off again. Also please add a video that shows the response to your nudging the roll and pitch sticks, so that we can tell that your control of the craft is correct as follows:
A) Nudge roll stick left, show that craft tilts left
B) Nudge roll stick right, show that craft tilts right
C) Nudge pitch forward, show that craft tilts forward
D) Nudge pitch back, show that craft tilts backward
Once that's been confirmed, we can start looking at other possible problems, like software bug that may be caused by your particular setup.
I had a similar thing with my quad, i got confused when i did the motor test in the CLI. I wired up the motors so when they were in order by the CLI test (1 pause 2 pause 3 pause 4 long pause) then matched the numbering system in the pictures on the wiki.
After a couple of hours of trying to work out why the quad was really unstable i figured out the motor test spins the motors one at a time in a clockwise direction rather than the crisscross way in the pictures
Also calibrating the ESC's throttle response could make a big difference too, if one is calibrated to a strange range it may get to full throttle quicker than the others and make it flip???
You probably should start a new discussion for this. Where do you get a DVB transmitter and how much would it cost?!
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