Re: First time EMC user (introduction)

["Richard Everett" <rick-at-skyko.com>]

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
>
>
>