servo dac offset

Is the axis homed? if not the actual angular positions dont really mean anything

As the tutorial states you must adjust FF1 so the feedback position neither leads nor lags the commanded position

You cannot just set a value you must adjust it till correct


If you want to scale in machine units you set the output scale (and limits) to the axis velocity in machine units per second at 10V

so if your axis moves 360 degrees per second with a 10V command to the servo drive, you would set

OUTPUT_SCALE = 360
OUTPUT_MIN_LIMIT = -360.0
OUTPUT_MAX_LIMIT = 360.0

and then FF1 should be 1.0

so if at 10V my axis move (at the end of motion chain... after reducer... is right?) at 1200 degrees per second I can set


OUTPUT_SCALE = 1200
OUTPUT_MIN_LIMIT = -1200.0
OUTPUT_MAX_LIMIT = 1200.0

and I can set FF1 = 1.0 ... Is right?

At these point:

MAX_VELOCITY = 72000.0
MAX_ACCELERATION = 72000.0 (or more if possible)

Is right??

But stability of system decrease ..... whitch parameter can adjust for make more stable the servo motor at stop command?

regards
Giorgio

Yes, if your A axis moves at 1200 degrees per second at 10V
you set

OUTPUT_SCALE = 1200
OUTPUT_MIN_LIMIT = -1200.0
OUTPUT_MAX_LIMIT = 1200.0

and then FF1 = 1.0 will be _CLOSE_ but still need tuning

If your axis moves 1200 degrees per second at 10V, then the maximum velocity
_must_ be below this so there is headroom for the servo:

MAX_VELOCITY = 1000.0

Maximum acceleration depends in your drive/load capabilities and error budget though
72000 degrees per S^2 means you can get to full speed (1000 degrees per second) in about
14 milliseconds which is unlikely.

I would start with a gentler:

MAX_ACCELERATION = 5000.0

or 200 milliseconds to full speed (at least to start)

ok ok ... just an other question .... the drive vlose itself the velocity loop ... I have to do the "0" in Lcnc and drive too? Or I can make the zero only in Lcnc?? The drive have C-/C (X - /X in Lcnc) zero signal .... How can grab it on Lcnc?

regards
Giorgio

If by "0" you mean homing, this is done entirely in LinuxCNC

If the drives quadrature signals include index, and they are wired to the 7I77,
LinuxCNC can home to index

I cancel before post ....

At last This my conf (ini file attach) .... it works quite good .... I change feedback signal to 2500ppr encoder direct ..... I have an other issue ... in pos move the machine go directly to quote ... in neg move it stop 8° first and than go to quote slowly ..... some reason or adjust to ini file for solve these??







hal scope image during working (+90 to -90° continuosly ...)




in addition I have to keep ferror 50 otherwise I get error tracking .... I tried to lower to the acceleration ... but I would be forced to lower it too ......

in pos move the machine go directly to quote ... in neg move it stop 8° first and than go to quote slowly ..... some reason or adjust to ini file for solve these??

Ok but why only in one direction? How can make simmetric the error ? Because I move only +90° and -90° continuosly but only at -90° have a problem when go to +90° the axis stop perfect. On the the servo motor shaft is connected to anything . No load on servomotor shaft .... I expect an error identical on both directions.

regards
Giorgio

This night I have an illumination .... the halscope posted before show a mouvement of axis from -90° to 90° ..... in these space (this is more or less my axis working area) is impossible that the axis go to 1000°sec velocity ... this is normal ... but I have set the acceleration to 5000° sec .... in the draw of hascope, I see that is noth enough ... probabily I need to go at max vel (not 1000°sec but 500°sec is probabily enought) in 20-30msec ..... without these my tuning is not possible ....

regards
giorgio