There is now several month that i try to optimize the tuning of a big octo-quad (carboncore cortex).
Carboncore use mn4010 motors and tmotor carbon 15" on the top, 16"on the bottom. This set up is working well with DJI Naza, but i never had a perfect attitude with my pixhawk. It constantly overshoot and begin to wobble, worse in loiter mode.
These lasts month i used smaller cheaper (less stiff) props, and it was acceptable (with a low P, High I and D). Now i wants to put the big props and start over. I got back to default PID's and tried with 20.000maH battery.
The setup is 8kgs. I was trying to adjust P with ch6 knob method. On this first flight, i had the feeling that somebody put my sticks (i'm french, and i feel that it will sound funny in english), as the copter made some movement on roll/pitch and yaw, all alone.
Finally, the copter falled on a side as was trying to land it... 4 props to the trash (160€...)
-Could i try an autotune with that kind of setup? anyone has experience with it?
-Generally, what kind of PID's should be applied on heavy copters
-Could anyone analyse the log, i checked all but i didn't find anything. Maybe mag or imu problem?
Thanks for your help!
I'm very happy these days because i solved all my olds problems, and closed 1 year of tunning!!
First of all, i have to say that the cortex is a wonderful copter, well designed and with an unbeatable stiffness for a folding octo. I never regrets my bought and would buy another if mine would be lost.
However, I think that the Carboncore's setup can't work (MN4010 370Kv with Tmotor 15" on the top and 16" on the bottom). The power consumption is really low, but the stability is a shame, because props are spinning really slowly, specially the 16". The loiter was a nightmare, constantly overshooting, really scary for a 8kg X8 with a nice camera under it!! Even the yaw was unconsistant, with suddenly changes of heading.
On my Cortex, the only hardware that is different from Carboncore's one is the esc's. I have rctimer opto 45A, they use tmotor ones. this is the last question i could have to explain that the "official" set up never works for me. I can't figure that the autopilot can be in cause, as they all works on the same principle (carbon core works with Dji and I with Apm, then pixhawk).
I mounted my pixhawk on dampers (i'll post some pics), and had really good results with vibration, the problem was'nt here.
Finally, i always had vibrations issues on my shots, with a Sony alpha 6000 (tried with an without steadyshot, worse with steadyshot...) and perfectly balanced props.
here are my solutions:
-Same motors but Tmotor 14" on the top, 15" on the bottom. I could believe i changed my copter. after a bit of tuning, I had the most stable machine i've seen, and the trust came back!! The consumption is a bit higher, but acceptable.
-10 000mAh battery. 9 minutes of flight time is enough for what i need, video recording. 20 000 works well anyway, but i rather a lighter machine for more agility (i often have to fly close to building and structures, as i'm specialised in building-industry filming)
-I bought a new pancake lens for my alpha6000, without steadyshot, and vibrations were significantly reduced.
-I changed the configuration of my gimbal, a DYS eagle eye. It was using compression dampers, and i tried to hang the gimbal to the dampers instead. Vibrations disappear...
Last thing, if you wants to buy a cortex with a arducopter setup, i would recommend a pixhack. The "sandwich" frame is not so wide in heigth, and you could do without an external damping system
Feel free to contact me if you are a cortex owner, I would be pleased to discuss about it.