02 Aug 2012 13:32 #22678 by LAIR82
I was wondering if anyone would have a calculation to establish a value for my "deadband" . I have read the section in the integrators manual and see the formula if using encoders, but we have resolvers on our machine, and i was not sure how to go about the math to establish a starting point.

Thanks

Rick

02 Aug 2012 16:52 #22684 by andypugh
Replied by andypugh on topic Re:Deadband
LAIR82 wrote:

I was wondering if anyone would have a calculation to establish a value for my "deadband"

Is there a problem with zero?

If so, just increase it until the problem goes away.

02 Aug 2012 17:11 #22685 by LAIR82
Replied by LAIR82 on topic Re:Deadband
Deadband sets how much either way of my commanded position it is allowed to deviate from correct?

02 Aug 2012 20:32 #22687 by andypugh
Replied by andypugh on topic Re:Deadband
LAIR82 wrote:

Deadband sets how much either way of my commanded position it is allowed to deviate from correct?

Not quite. It sets a band around the setpoint where the controller doesn't even attempt to correct the position error.

03 Aug 2012 03:44 #22701 by jmelson
Replied by jmelson on topic Re:Deadband
LAIR82 wrote:

I was wondering if anyone would have a calculation to establish a value for my "deadband" . I have read the section in the integrators manual and see the formula if using encoders, but we have resolvers on our machine, and i was not sure how to go about the math to establish a starting point.

Thanks

Rick

Take whatever your resolver converter produces when converted to axis units
and multiply by 1.5 for a starting value. So, if you have 4096 counts/rev and
a 5 TPI leadscrew, then your resolution is 1/(4096 * 5) = 0.0000488 inch.
So, a good starting value would be 7.32E-5
You want to keep this value as small as possible while suppressing annoying
servo dither. If it is too large, it adds a discontinuity in the servo transfer
function as it crosses zero, and can make the loop unstable.

And, of course, if you DON'T have any dither, then use zero.

Jon

06 Aug 2012 12:40 #22902 by LAIR82
Replied by LAIR82 on topic Re:Deadband
I set it to zero and started from there going down on the count until it got "nervous" and then backed off a little bit. Nice and quiet now and no jitter on the display. The servo was humming before and I think it was "hunting" and I just did not realize what it was actually doing.

Thanks

Rick