acceptable accuracy resault 7i77

hello gentelmen,

excuse me, I am recently playing around the 7i76e+7i77... 

what should be acceptable resault of PID tuning with 5mm ballscrew and TTL 4096 increments at the single revolution please? it goes in 0.002mm in place error(oscilation +-0,001 around cmd value) and in maximal 0.02mm error during rapid movement without load..

I think there should be limitation of single edge signal resolution oscilation movement of servo which are (5mm/4096)*(2 units of encoder which are conncted together with single signal edge) = aprox. 0,002mm ??

thanks

regards Slav

You can add some deadzone to eliminate the +- 1 encoder count dithering
though it does compromise accuracy somewhat and is not effective when an external force is applied (say on a vertical Z axis)

thanks 

I still can not find bit resolution of differential analog outputs from 7i77.. I need it for setup of deadband in mV to driver probably.

I just found 13bit in the mesa manual. Should it be the real one value please?

ANALOG OUTPUTS
OUTPUT ACCURACY -0.8 +0.8 %FS
OUTPUT CURRENT ---- 5 mA
******************* OUTPUT RESOLUTION ---- 13 Bits *******************
RIPPLE AND NOISE -0.1 +0.1 %FS

I think it should be because drive has right same value ...

Note that that's 13 bits of accuracy per direction so about 1.25 mV

Also note that the PID components deadband is in error and
that deadband is relative to encoder resolution not analog resolution

yes there is difference between them. Deadband caused by bit resolution has to be setted in servo configuration and deadband of feedback resolution has to be setted in PID configuration .ini or .hal files.

I just try setup alone servo for swap purpuse at real machine, which it is now running on pulse/dir without feedback... only via servo position loop which after long using casued a little bit of position error because of pulse resolution.

Thank you,

Slav