Pixhawk Autotune motor stall

[PhillNZ]

Have built Tarot 650 ironman with the following:
SunnySky X4108S-14 KV480 motors
ZTW Spider 30A opto ESC SimonK program
Gemfan (T-motor type) 16 x 5.5 blades
Zippy 4s 5800mhr battery
SkyFly Taranis X9D & X8R-PCB
End weight 2058gm without gimbal & GoPro
added 274gms of weight to equal gimbal etc.

Read the warning about low KV motors and the possible sync issues with the rapid throttle advancement during autotune, harnessed the quad and sure enough with rapid throttle changes one of the motors stalled out so no auto tune for this machine.

Just wondering if there will be a solution for this as being new to this its hard to know what one should be aiming for when making the adjustments.

Comments or [FONT=arial, helvetica, sans-serif]criticisms gratefully received

cheers
phill[/FONT]

 

[Av8Chuck]

Curious how many poles the motors have? As I understand it SimonK firmware has timing issues with higher pole count motors (18-24). If its the same motor that's stalling then you might try switching out the ESC with one that doesn't have SimonK firmware and see if the autotune will complete and then swap the ESC back when tuning is complete. I doubt that it would make that much difference to the flight characteristics.

 

[PhillNZ]

Curious how many poles the motors have? As I understand it SimonK firmware has timing issues with higher pole count motors (18-24). If its the same motor that's stalling then you might try switching out the ESC with one that doesn't have SimonK firmware and see if the autotune will complete and then swap the ESC back when tuning is complete. I doubt that it would make that much difference to the flight characteristics.

Its hard to get any info on this particular sunny sky motor, but I believe it is only 14pole. I haven't be game enough to try the auto tune function as I decided to test the for the motor stall by tethering the quad and advancing and retreating the throttle very rapidly, and it appeared from this one of the motors seemed to become slow in response. Haven't been game to try an autotune incase it ends badly. Don't have spare ESC's etc, until the next build is decided upon.

 

[R_Lefebvre]

I don't think there will be a solution to this problem, because the problem does not exist in the Arducopter firmware. The only thing we could do would be to create a slew-rate limiter, which would limit the rate of change of the throttle signal. It would be kind of a silly thing to do, as that would defeat the purpose of running SimonK. You could just as easily not run SimonK ESC's.

 

[PhillNZ]

Thanks for your response, my description was inadequate I did read the referral to the simonK aspect and should have asked if there was a work around as you have suggested. I'm struggling to sort the hay from the chaff somewhat as regards the periphials, can I ask for a recommendation for a non simonK ESC. I've really enjoyed getting to grips with the Pixhawk and its setup, mainly as its both a quality product and the backup information on the web is both well set out and very comprehensive. There still however for myself is the gap between lack of type experience and knowing the best that can be achieved.
I'm going to start to slowly tweak up the basic settings until I hopefully identify the "sweet spot".
Kia Kaha

 

[R_Lefebvre]

I can't recommend many ESC's, as I don't use a lot. Right now I have 2 quads, both running Hobbywing Quattros. They're fine. I suspect just about any ESC not running multi-rotor specific code will work fine. I am keen to try out HobbyWing's new Xrotor ESC's.

 

[jdennings]

I gave up with Simonk esc's on pancake/low kv motors close to a year ago as I had the exact problems mentioned. First time it happened I blew an esc and motor on the bench. (Also had to do with not connecting esc ground wire to pixhawk, a big mistake as I should have known better). At about the same time on another copter I also had autotune crashes due to sync problems with both simonk and non simonk. Since then I've used Hobbywing Platimum escs and no problem whatsoever.

On a new build no matter what esc/motor/voltage and just to make sure, I always first rev up agressively looking/listening for any timing/sync issue on the bench with all props on. If none I then fly the bird in manual mode inducing nasty roll and pitch twitches similar (worse) than autotune as a "test" of flight worthiness, also knowing that I have a better chance of recovering if something goes wrong than if the problem gets revealed later while auto-tuning. Since then all a-ok.