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Submitted by gary1 on Thu, 12/21/2006 - 14:21

Hi,
I have a single axis which performs regular position moves (PA,PR) as well as gearing. My motion with regular moves is smooth, but the geared motion is a bit rough. I am fairly sure the problem is related to the relationship between aux encoder resolution and my servo feedback resolution (effectively my gear ratio).

I can improve the smoothness by lowering my servo feedback resolution from the drive (lowering my gear ratio) but I am sure this is giving me reduced accuracy and more difficulty tuning properly (cannot increase gains very much).

Should I choose an aux encoder with higher resolution instead?
Is there a "rule-of-thumb" for high gear ratios? (ie. keep as close as possible to 1:1 for best performance)

Also, my system has inertia ratio < 2 and is reasonably stiff.

Comments 2

Galil_AndyH on 01/03/2007 - 17:45

Gary,

What are the GR and GA settings that you are commanding? Is the Aux encoder higher resolution than the feedback encoder?

There is no rule of thumb for gear ratios. But if you have a low resolution master and a high gear ratio, then you will be commanding large jumps on the slave. This could be what you are seeing.

Is the geared motion rough through the entire gearing, or just when you initially engage the gearing? If it is just in the beginning, then you may want to use ramp to gearing.

gary1 on 01/14/2007 - 11:59

Yes my master encoder resolution is lower than than the slave and I do have rough motion at all times. I will try a higher resolution master to see if it improves.

Also, I am using a DMC1410 which does not have a ramp to gear function. I have written a small subroutine to ramp up to gearing which seems to function fine (it is based on threads in the software section of this forum).