(EMC)
Subject: [Emc-users] Servos cannot calm down -- maybe I should go away from
velocity mode in amplifiers?
I posted a message to this list that my servo motors cannot calm down
after a motion.
Right now my amplifiers are set to velocity mode and I use a
tachometer for velocity feedback. So, the
shouldn't this be done systematically? (it could be done all in emc
with halscope)
First tune the velocity loop in amp
-send a step response to the drive (square wave) and scope the responce.
-Adjust the loop gain of the amp to get the best waveform - (match the
square wave the best you can)
Igor Chudov wrote:
>
> I am now thinking that I should reconsider my entire approach and use
> a different mode to avoid two loops per axis.
>
No, I think you need to retune the Y amplifier, I think that is where the
oscillation is. Just turning down both the tach and command gain should
help.
I would turn the posts down a bit and see if it makes much difference.
If it does then turn them down a bit more. If it makes no difference
then it could be that the drives aren't the problem.
Take a photo or mark the pots before you tweak them. That way if
something goes wrong at least you knw
- Igor
On Mon, Sep 13, 2010 at 11:13 AM, Leslie Newell
wrote:
> Yes, with this loop, stability is more important than accuracy. You can
> still get get very good results with no velocity feedback at all.
OK, I will turn the pots on amps way down and will see how it goes.
i
> Les
>
>> Maybe I
Yes, with this loop, stability is more important than accuracy. You can
still get get very good results with no velocity feedback at all.
Les
> Maybe I should turn the gain on the amplifier loop way down?
>
> i
>
>
---
On Mon, Sep 13, 2010 at 10:50 AM, Thomas Powderly wrote:
> Two loops can be a problem
> the 'outer' loop has to be the master
>
> we used to tune the hardware loop really 'tight'
> and had jitter at the cnc control loop
> we ended up 'de-tuning' the hardware loop to soften it a bit ( reduced gain
Two loops can be a problem
the 'outer' loop has to be the master
we used to tune the hardware loop really 'tight'
and had jitter at the cnc control loop
we ended up 'de-tuning' the hardware loop to soften it a bit ( reduced gain )
its not hard to try with old school amps with pots, a bit more ted
Two velocity loops shouldn't be a problem. Have you tried reducing the
amp gain? Somewhere the amps must have controls for the loop gain. Try
turning the gain down. It doesn't matter if the amp velocity loop is a
bit weak as EMC's loop will compensate.
Les
On 13/09/2010 15:37, Igor Chudov wrot
I posted a message to this list that my servo motors cannot calm down
after a motion.
Right now my amplifiers are set to velocity mode and I use a
tachometer for velocity feedback. So, the amps themselves have a
velocity loop that they close. There is essentially two loops per
axis, one in EMC2 an
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