RE: [CAD_CAM_EDM_DRO] Re: Servo drives- Mariss Rutex PID and Tuning with a O-Scope

The encoder output (Velocity) would be "integrated" over time to derive
a position.

Plotting the position over time (O-scope or other real-time strip
recorder) will show the servo settle/under/overshoot characteristics.

Settle time is one aspect (optimal settle time has some overshoot),
Some applications may not tolerate overshoot and would prefer slower
approach to the final position (less optimal settle time, less
overshoot)

Poor (excessive) feedback gain (P & I terms?) can cause divergent
oscillations, (overcompensating builds up, hunting grows, hit the
E-stop.)

In some applications(rotary) encoder error can accumulate and must be
accounted for.

Usually,(theory) a step function is the std stimulus and optimal PID
params can be derived from the response from this std stimulus.

Some sophisticated control systems will model this response in a
DSP(real-time) and can derive instantaneous position with an open loop
motor (closed loop is modeled in DSP) usually there is an fail-safe
index. (not usually in milling applications)

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Alan Marconett
Sent: Friday, May 13, 2005 10:23 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: RE: [CAD_CAM_EDM_DRO] Re: Servo drives- Mariss Rutex PID and
Tuning with a O-Scope

Hi Mariss,

I have no wish for you or anyone else to malign a respectable
businessman!
I've talked with the owner in the past, he's a HAM, and a real nice guy.


I'm not actually interested in comparing your products with his as
others
might be, Rather, I'm interested in the process of tuning a drive
system. I
want to know how to "INSTRUMENT" a system to study how the PID controls
it.
Call it PID 101.

I'm asking what I can do to "observe" what's going on with servo drives!
I
have good 2 and 4 channel 'Scopes available and I can probably read the
encoder into a PC. I will be able to display the waveform on the test
point
and the step line as you describe in the G320 manual under servo tuning.
It
would be useful to be able to "read" the three pots as well for the PID
values.

Thanks,

Alan KM6VV

> -----Original Message-----
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Mariss Freimanis
> Sent: Thursday, May 12, 2005 10:58 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] Re: Servo drives- Mariss Rutex PID and

Tuning

> with a O-Scope
>
> Tuned or mistuned, a servo will arrive at the correct place. All
> tuning does is optimize the settling time. This for most applications
> is of little consequence.
>
> Rutex is a competitor to our drives but I can say nothing bad about
> them because they have always been a fair and honest competitor. Like
> us, they build good drives at a good price.
>
> There are people that prefer them just as there are people that
> prefer our drives to theirs. It's a Coke versus a Pepsi kind of
> thing. I'd rather not be goaded into putting a fair and good
> competitor into a bad light. The world is big enough for the likes of
> us and them and a dozen more.
>
> Mariss
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
> <dave_mucha@y...> wrote:
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Alan Marconett"
> <KM6VV@a...>
> > wrote:
> > > Hi Dave,
> > >
> > > What's this about PID tuning? What are the inputs to the 'scope?
> > Some sort
> > > of encoder or tach on the shaft? Plus some display of the input
> > commands?
> > >
> > > Alan KM6VV
> >
> >
> > I took a brief look at the Rutex site and they claim a faster and
> > better PID for more stable control. Faster than what?? I think than
> > their old one ?
> >
> > They show a screen shot of the stable motor operation. And, I
> gather
> > that screen is from the software monitoring the motor paramters ?
> >
> > Also, the people who have po-poo'd G-320's seem to all complain
> about
> > tuning. (one was upset that he couldn't tune it without having to
> > spend the extra $$ for an encoder) but also, everyone who has used a
> > scope to tune them speaks highly of the drive.
> >
> > Since there are a few pc-scope free-ware programs, I assumed that
> > people are using them to tune the servo drives, and that being the
> > case, I also assumed that someone would have done a "ho-to" about
> it.
> >
> > I also assume that 90% of the people tune them quickly and easily or
> > at least satisfactorily, from the methods at hand.
> >
> > Dave
>

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