I have some kind of weird throttle ESC issue... any advice?

[zektiv]

I just built an Atom v2, relatively simple to put together.

Thing is, my motors aren't smooth at all - in fact, take-off is a hot stuttering mess until I'm at like, 65% throttle, and then I can fly but it certainly doesn't feel 'locked in'. My Tiny Whoop feels more locked in.

I've put it on CF, armed the motors, and kicked up the throttle just to see what's going on. Here's a video:

https://youtu.be/gsqNf9cwOQ8

That's using the controller (Taranis x9d+), and an XSR. If I just use the sliders to push the motors from within Cleanflight, it's all smooth as can be.

That can't be normal. The problem is I have no idea how to troubleshoot this or diagnose the issue beyond saying "this can't be normal." Any advice from the experts?

Thanks!!!

 

[rockyboy]

I've had a similar problem (sometimes the motors would wind up smoothly, other times they would jerk) and was able to fix it by adjusting the timing on the ESC's. But since you're able to adjust the throttle from Cleanflight and it's smooth there, you might be looking at some other problem that's beyond me.

 

[Craftydan]

The key symptom is "smooth with the sliders". if that's good, everything between the flight controller output and the prop is good. So the problem is upstream form there . . .

The jitter you're getting (from your description -- can't look at the vid here) sounds like trouble in the control loops.

First I'd look at the flight controller mounting -- is there any play in it? a "little loose" in the mounting will do terrible things when the control board is trying to keep the frame steady while simultaneously rattling around in it's mount.

Next I'd check for vibe injecting noise into the sensors -- if you spin up with a prop using the sliders does it spin up smoothly? Is there vibe on the airframe when you do? a little? a lot? Run the motors up one-by-one to isolate. 3" props would be crazy hard to balance, but if it's creating a very large jitter it needs something to reduce the vibe. keep in mind the sensor plots in the configurator can help you by playing the hot-cold game with balance using a small piece of tape on the prop.

Also, double check your motor mounts to see if they're properly tight, and that the bolt ends aren't more than a thread or two beyond the inside mounting plate (too long, and the end of the bolt starts messing with the magnetic field . . . really too long crimps a motor wire and destroys the motor).

Finally, when all else fails . . . tune the PID loops (this is probably your problem, but the other two things are good to do and makes it fly better anyways ). From the sounds of it, your P (and maybe your D) are too high. I'd cut your D in half and drop P by 10% increments to see if this settles out.