Hello to all
I build a big X8 and i suspect some think happen with my rc mapping when octo starts it feels unresponce with big corrections and hard landings result and some flips whatever i do in P doesn’t affect the system so my next think is the rc mapping i use sbus futaba receiver direct pinned to pixhawk but my rc in and out in channel 12 and 4 look strange also the roll and dess roll looks opposite
I enquiry the LOG
Any comments are welcome
Replies
With such a big prop and low KV configuration, your PIDs are way too low and you craft is a bit underpowered.
You should ideally hover at 50% of throttle. In your case you barely get the required throttle to hover (minimum 14Kg) at above 60% of your throttle.
To solve the issue, you either reduce the size of your props (motors will spin faster) and increase your PIDs significantly.
Please show detail information on your X8; motors, batteries, weight, and propellers.
kde 27,6 x 8.9 props
U10 Motors 2 x 22Amp batteries
Tiger motor 60A esc
14 kg full without payload
Really guys you think is an underpower setup?????
at 60% i must have 12 kg of thrust and in 100% 22kg how is possible to be underpower
Are you using 6S? For such low kv motors, you need a very good reactivity. If you can secure 1 motor with its props and try to shake your throttle stick you could check response time of your Esc/Motor/Props. If too slow, you can somehow compensate with high PIDs but you may experience problems in flight.
Large props = more inertia, with low kv motors as yours, you do need a prop that follow very well throttle outputs. Regenerative braking helps, maybe you could try KDE ESCs?
also after further investigation in raw data looks motor 1 ,7 and 8 be asynchronous in stabilize motor and with no move on frame please see video here
The link to the video is broken...
I had a similar problem with a big quad and slow big props. I had to increase rate P and use a lower STB_P/R value (something like 3 maybe) to limit the angular speed of the copter. At the end I changed the hardware setup: motors were just not reactive enough to accelerate large props.
May you tell what motors/props combo you are using?
Antonis,
It seems like the vehicle is under powered. Maybe the KV of the motors is too low?
The reason I say this is that when it's flying the motors are at >80%. You've probably noticed that during take-off you need to give nearly full throttle on the transmitter? For good performance a vehicle really should hover at absolutely no more than 70% and really under 60% is best.
log file is here
24.BIN
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