Re: First time EMC user (introduction)

[Ray Henry <rehenry-at-up.net>]

Richard

I talked with Mariss about running the signals to both a 320 and a dro 
card the other day and he suggested that a dual opto isolator would do 
the trick.  This approach would also allow for dual voltages for these 
encoders.  I've got the Kulaga/Mauch dro card working well here with 
smdromod.o. 

Ray 



On Tuesday 01 October 2002 10:55 am, you wrote:
> Thanks for the explanation.  I *thought* I was doing things correctly
> when the computor "crapped out", but I was not sure if I was missing
> something in the ini file, like <crapout = true> or something.
>
> After moving that massive table around even with the slow speeds using
> the Gecko drive, I at least would like to close the loop back to the
> controller, not just use the error signal from the gecko drive.
>
> Richard
>
>
> ----- Original Message -----
> From: "Ray Henry" <rehenry-at-up.net>
> To: "Multiple recipients of list" <emc-at-nist.gov>
> Sent: Tuesday, October 01, 2002 7:18 AM
> Subject: Re: First time EMC user (introduction)
>
> > Richard
> >
> > I guessed it but I was thinking even worse -- like the 125000 ppr's
> > that I ran into the other day.  Others have explained the fix.  You
> > are fortunate that the Gecko pulse multiplier will get you in range. 
> > Until then, you can run with the large values in the ini by reducing
> > the velocity component a lot and watch the machine crawl.
> >
> > The PC will behave this way (crap out) when the product of max
> > velocity and input scale is way over the top.  Freqmod just loads and
> > then everything gets very slow.  Steppermod kills the PC and
> > everything near it so that you have to reboot.  If you get some
> > unexpected behaviors after a crash like this, you may have to reload
> > a package or two.
> >
> > Ray
> >
> > On Monday 30 September 2002 11:09 pm, you wrote:
> > > Hi Ray,
> > >
> > > I responded to Jon with a rather long post, so I will not repeat
> > > all of that here.  Thanks for the tips.  You were right, although I
> > > bet you didn't realize my encoders are 10,000 counts/rev in
> > > quadrature!!!!  I need 50,000 steps to go one inch :-(
> > >
> > > Time to rethink my electronics, huh?
> > >
> > > Richard
> > >
> > >
> > > ----- Original Message -----
> > > From: "Ray Henry" <rehenry-at-up.net>
> > > To: "Multiple recipients of list" <emc-at-nist.gov>
> > > Sent: Monday, September 30, 2002 11:26 AM
> > > Subject: Re: First time EMC user (introduction)
> > >
> > > > Hi Richard.  Welcome to the "Chips" (our mascot) fan club.  You
> > > > may have seen him a few times during the install.  The micrometer
> > > > is so that he can prove just how accurate the EMC can be.  The
> > > > dead-blow hammer is to make the part fit!
> > > >
> > > > Steppermod is a binning procedure and may well produce periods of
> > > > inactivity or reduced activity that will be obvious with a scope.
> > > >  We generally speak of jitter when we consider how well it puts
> > > > out pulses. You might try freqmod.  There you will find an
> > > > attempt to generate frequencies rather than pulse batches.  Both
> > > > of these are limited in different ways by the ability to generate
> > > > pulse trains.
> > > >
> > > > The 350MHz PC should run freqmod with a period around 0.000035. 
> > > > You will not get a real high speed pulse rate from it.  Better
> > > > with steppermod than freqmod.  Better yet with a servo card.
> > > > <hint>
> > > >
> > > > The machine sounds great.  There are a few commercial machines
> > > > that have been retrofitted and a couple others who are working on
> > > > integration of the EMC to this level of tool.  Most of these use
> > > > or plan to use a full servo feedback system.
> > > >
> > > > Two things worry me just a bit about the Gecko 320 in this big
> > > > machine application.  The first is that you will sacrefice a lot
> > > > of speed for two reasons.  The first is that you will not get
> > > > full current for the motors and that will reduce acceleration a
> > > > bunch. The second speed loss will depend upon the number of
> > > > pulses per unit of the existing encoders.  The Gecko pulse
> > > > multiplier board might help this quite a bit.  You can think in
> > > > terms of 5k to 10k pps for your computer so you need to see how
> > > > many pulses it will take per unit of travel and then you will
> > > > know the top end for rapids.
> > > >
> > > > The second concern is with open loop operation.  You should not
> > > > loose pulses with the step and direction Gecko, at least not like
> > > > you would with steppers but there is still something that bothers
> > > > me about a computer making assumptions about where an axis might
> > > > be on this big of a machine.  The Gecko will fault after 128
> > > > pulses sent to it are unanswered by the encoder but that can be
> > > > quite a distance compared to normal following error settings for
> > > > a servo system.
> > > >
> > > > It sounds like the encoders feed the drive amps and they compute
> > > > velocity from the pulse train.  If this is the way the machine
> > > > ran, those signals must also have been fed into the control for
> > > > positioning.  You might well be able to make a single encoder do
> > > > double duty with a PPMC (Jon Elson) STG,  Studio Ferraris,
> > > > Vigilant, or whatever servo card(s) as well.  Or perhaps you
> > > > could add a second encoder for positioning.
> > > >
> > > > You might look at tkio and iosh for a possible path to produce
> > > > logic and work io pins for your tool changer.  There has been
> > > > some talk about writing an interface that would allow us to use
> > > > classicladder and MAT but it isn't there yet.
> > > >
> > > > M2CW  Hope this helps
> > > >
> > > > Ray
> > > >
> > > > On Monday 30 September 2002 11:14 am, you wrote:
> > > > > Hi everyone,
> > > > >
> > > > > I have just installed EMC and linux using the BDI cdrom image.
> > > > > After figuring out that I had to log in as root, and after
> > > > > setting the emc.ini file to steppermod and minimilltask (it
> > > > > would not come out of estop with bridgeporttask) I managed to
> > > > > get step signals on pin 3 (X axis) of the parallel port.  I
> > > > > monitored these with my digital oscope, and saw an interesting
> > > > > thing.  I selected manual control, and then set the x axis to
> > > > > move 1 inch.  My ini file had the max acceleration at 2, and I
> > > > > captured the pulse train on my scope.  It looked about right I
> > > > > guess, with the pulse frequency accelerating to 2 khz.  The
> > > > > strange thing was that after the pulse train had fully
> > > > > accelerated, there would be a 1 khz pulse about every 8 or so
> > > > > of the 2khz pulses.  I don't know if this is some latency
> > > > > issue, or perhaps that is when some other task is running?
> > > > >
> > > > >
> > > > > I am running on an AMD K6-2 350mhz.  I am going to be using
> > > > > this to control a rather large Shizuoka B-3V bed mill, with
> > > > > Fanuc model 0 brush DC servo motors (60V 12A) on the x and y
> > > > > axis, and a Fanuc model 5 bruch DC servo motor (90V 12A) on the
> > > > > z axis.  I am not 100% positive, but I believe there is not a
> > > > > tach on these motors, just a quadrature encoder (called a pulse
> > > > > coder by fanuc).  I already have two Gecko G320 servo drives
> > > > > (take step,dir signals) which should work for the x and y, so I
> > > > > am going to start with those.  I would get the servo to go
> > > > > card, except that I am not sure if I would be able to use
> > > > > analog input servo amps without a tach on my motors, so why not
> > > > > just get one or two more parallel ports?
> > > > >
> > > > > Anyway, I want to really dig into this.  I like the idea of an
> > > > > open source machine controller.  I discovered the (rather
> > > > > large) message archives, and I will try to answer most of my
> > > > > questions there so as not to clog the message board with
> > > > > redundant newbie stuff.  When I get a bit more experience, I
> > > > > would like to add to the EMC knowledge base, as I am going to
> > > > > need to do a few special things like controlling my 20 position
> > > > > ATC on the cnc mill.
> > > > >
> > > > > Back to the scope,
> > > > >
> > > > > Richard