Servo stepping on pitch changes

I'm running Align BL815H servos on cyclic, and they are stepping instead of being smooth. It's not noticeable when moving collective slowly, but at medium to fast speeds the servos judder and everything rattles.

The servo pulse is 1520µs and frequency is 333Hz, which match what the NEO puts out AFAIK. I'm using a 2 cell LiPo receiver pack. The 2nd video has 2 servos unplugged, just showing the single servo with juddering, so I guess it's not a power issue.

The video might not show the juddering clearly, but you will be able to hear it. The swash moves smoothly and there is no sticking when moving by hand.

Cyclic 3 on YouTube

Cyclic 1 on YouTube

Any ideas?

Thanks
Richard



Edited 1 time(s). Last edit at 10/17/2017 05:17PM by RichardV.

When I put the servos on an analog servo tester at various speeds/loads, they are completely smooth.



Edited 1 time(s). Last edit at 10/18/2017 09:10AM by RichardV.

NEO drives with 166Hz on the Swashplate.

IMO this is normal. The servos are so fast, that they start to see the framerate as single steps already.

so long ... Uli
http://www.vstabi.de

Hi Richard,

VBars actually outputs 144 Hz to the swash plate servo ports, as a side note.

I have already seen that with ultrafast HV servos, both on the tail and on the swash plate, and discussed it with our developer.
The reason is probably indeed the speed of the servos, almost instantly moving into the next position, and then fluttering with the almost imperceptible tremble of your fingers, on the stick.

If the servos run smoothly wenn controlled by the VBar (move the model, see the sensor-controlled motion), all should be well.

Kind regards

Eddi

Born to fly ...
forced to work.

Thank you for the replies. I tried again and created the servo movement using an oscillator macrocell, and it does the same thing.

I think you're right about the servos being fast, and under light or negative load the servo motor keeps stop/starting/reversing even though the requested movement is uniform and in one direction.

Consider this one solved

Cheers
Richard