> Date: Tue, 13 Oct 2009 08:06:00 -0700
> From: [email protected]
> To: [email protected]
> Subject: Re: [Emc-developers] hostmot2 stepping folowing error oddity
>
> On Tue, 13 Oct 2009, Sebastian Kuzminsky wrote:
>
> > Date: Tue, 13 Oct 2009 08:57:34 -0600
> > From: Sebastian Kuzminsky <[email protected]>
> > Reply-To: EMC developers <[email protected]>
> > To: EMC developers <[email protected]>
> > Subject: Re: [Emc-developers] hostmot2 stepping folowing error oddity
> >
> > Peter C. Wallace wrote:
> >> On Mon, 12 Oct 2009, Chris Morley wrote:
> >>> I'm having a little problem with a hostmot2 stepper setup.
> >>> I get following errors that I can't track down a reason for.
> >>
> >> Is it possible you simple dont have enough hardware headroom to reach you
> >> max
> >> velocity? With 200 usec StepLen and 200 uSec StepSpace, the maximum step
> >> rate
> >> the hardware can generate is = ~2500 Hz, I just glanced at the ini file but
> >> doesn't a Scale of 2800 mean 2800 steps per inch? If so the maximum
> >> velocity
> >> should be about 10% less than 2500/2800 (10% for headroom). about .8 inches
> >> per second.
> >
> > I agree it's a "max physical step rate" vs "trajectory-planner max
> > commanded velocity" problem, but i think there is no headroom problem.
>
> Well semantics... to me its a _hardware_ headroom problem, the hardware
> stepgenerator is being asked to step faster than its capable of stepping.
>
> Chris: can you try setting max_velocity to .8 so theres no chance the
> trajectory planner can outrun the stepgenerator? I think all bets are off
> without this.
>
I will try this later hopefully tonight.
Interestingly the reason I was using 100 inches per minute (1.667 ips)...
Pncconf has a 'tune test' that sets the hostmot2 stepgen's
max velocity and max acceleration. It would let me move at
aprox 150 inches per minute. It does not keep track of following error
though. So I detuned it to 100 ipm and ran EMC. I'm not sure how
hostmot2's stepgens decide on whether it can or cannot move at a
specific drive timings and max speed etc.
But all that aside I still don't see why moving negative and positive
is so dramatically different - but then again I know nothing about
stepgenning and trajectory planning :)
Chris M
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