AB 1746-QS, -QV, open vs. closed loop

Can anybody enlighten me as to the difference between these two?

It appears that the -QS is for when you want one axis to slave
to another in lock step.

But, in the -QV, are you not maintaining a position as well??

[email][email protected][/email] said:

Can anybody enlighten me as to the difference between these two?

Click to expand...

The 1746-QV is basically a single axis open loop controller that uses position feedback as a limit switch. The 1746-QS is a hydraulic servo positioning system that can coordinate 4 axes and generate smooth motion profiles.

[email][email protected][/email] said:

It appears that the -QS is for when you want one axis to slave
to another in lock step.

Click to expand...

Yes, the QS can synchronize the four axes. It can move the axes together at the same speed and postion or do linear interpolation where axes can start at different places and go to different destinations but arrive at the same time. BTW the QS can do open loop control too.

[email][email protected][/email] said:

But, in the -QV, are you not maintaining a position as well??

Click to expand...

QV doesn't appear to control position by the documentation. It doesn't appear to even use the difference in counts to do a closed loop speed control. It just appears to use the feed back as a fancy limit switch to trigger the next voltage that is output. I helped make one of these go a few years ago. I only remember the QV having openloop control as in the documentation.

I can tell you anything you want to know about the QS.

open vs. closed

That would seem to answer my question. This morning I read through
the -QV manual very carefully and concluded the same thing as you
have stated...that the position is simply a trigger to the next
stage of acc/dec values.

For my application, the -QS would appear to be a better match,
since I have vertically mounted cylinders and I am trying to 'hold'
a position after I complete the move to that position.

Thanks again, Peter. This is the place for real answers from people
who have actually used this stuff.

wink-wink, nudge-nudge

Now that I've looked at Allen Bradley's 'Hydraulic Configurator'
for the '1746-QS' module, I know more about it than I first did.

I mean, come on, at least they could change the screen color, to
disguise it (HC) from its true source!

Thanks again.

An added benefit.

The learning curve will be VERY short.