I think the error of this approach (using N times higher accel/vel) is
coming from the piecewise linear approximations of the curves going bad.
If you try to follow a curve N times faster, then there are N times fewer
samples along that curve for a fixed time sampling period.  That introduces
errors.  There may be others but thats at least part of it.  Its the same
problem w/ discrete time vs continuous time systems.  There is divergence
between the solutions as the sampling rate goes down.


On Thu, Oct 13, 2016 at 3:08 PM, Todd Zuercher <zuerc...@embarqmail.com>
wrote:

> I was just working at this a little bit.   The first thing I did was to
> modify time.comp, to make a new sim_time.comp.  The sim_time.comp is
> basically just the same as the regular timer component with an input pin
> added to scale the time to what ever factor you speed up the simulation
> run.  Then I made a dummy config of one of our machines with all the
> velocities and accelerations increased by 1000x, and test ran a few things,
> the results were not quite as good as I had hoped, but were way better than
> the old estimations. Is it possible that some of the inaccuracy came from
> the fact I was running it in a VM?
>
> The timer scaling pin was a really simple mod, would there be any interest
> in adding that to the regular release?
>
> ----- Original Message -----
> From: dan...@austin.rr.com
> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
> Sent: Thursday, October 13, 2016 2:24:53 PM
> Subject: Re: [Emc-users] Hacking a sim runtime mode
>
>
> ---- Chris Albertson <albertson.ch...@gmail.com> wrote:
> > On Thu, Oct 13, 2016 at 9:00 AM, Peter C. Wallace <p...@mesanet.com>
> wrote:
> > > On Thu, 13 Oct 2016, dan...@austin.rr.com wrote:
> > >
> >
> > > I just tried a real time Mesa Ethernet config with maxvel = 120000 IPM
> (2000
> > > IPS = 20 MHz step rate at present 10000 steps/In scaling) and maxaccel
> 20000
> > > IPS/S (52 Gs) with a 1 KHz servo thread, and it works fine (Peak
> following
> > > errors in the 1-2 mill region)
> >
> > The problem to be solved is getting an estimate of the time required
> > to complete a job.   Does the above do this accurately?
>
> Yeah I want to know this.  I can run a job for real vs "fast sim" and
> compare.  One prob is the cycle time only goes down to seconds AFAIK.  If
> it's 100x then that's over a minute and a half it could be wrong, but
> that's still good enough as long as it's not estimating a very short job.
>
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