Re: [Emc-developers] Parameter update rate
On Sat, 27 Apr 2019, Marius Liebenberg wrote:
Date: Sat, 27 Apr 2019 16:54:47 +0200
From: Marius Liebenberg
Reply-To: EMC developers
To: emc-developers@lists.sourceforge.net
Subject: Re: [Emc-developers] Parameter update rate
Thanks Andy
Just to make sure that I understand it correctly.
If I read the position or velocity at every servo loop at say 1ms, and my
step rate is at 100khz, I must still work out the steps required between
every position given at the loop rate.
The motion component provides position waypoints and current velocities every
servo period. A step generator typically uses these to set the current
velocity by using the requested velocity from motion and making small
corrections in this velocity based on the difference in motions position
waypoint and the actual stepgen position counter. This correction is needed
because of small errors caused by LinuxCNC/stepgen timebase differences,
imprecise read and write times, and velocity setpoint granularity.
This correction can be done in the stepgen itself or in LinuxCNC (via PID or
thr step driver)
On 4/27/2019 12:18 PM, andy pugh wrote:
On Sat, 27 Apr 2019 at 09:49, Marius Liebenberg
wrote:
At what rate is the velocity or position parameters of the StepGen
updated? Is that rate constant?
It should be the servo thread rate, and constant.
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Re: [Emc-developers] Parameter update rate
You calculated the step rate? It might be close to 1ms and in such sending position will give plenty of jitter, for example switching between two/three pulses in each period or probably worst case one or two pulses. > Thanks Andy > > Just to make sure that I understand it correctly. > > If I read the position or velocity at every servo loop at say 1ms, and > my step rate is at 100khz, I must still work out the steps required > between every position given at the loop rate. > > On 4/27/2019 12:18 PM, andy pugh wrote: > > On Sat, 27 Apr 2019 at 09:49, Marius Liebenberg > > wrote: > > > >> At what rate is the velocity or position parameters of the StepGen > >> updated? Is that rate constant? > > It should be the servo thread rate, and constant. > > > > > > > > ___ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers ___ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
Re: [Emc-developers] Parameter update rate
Thanks Andy Just to make sure that I understand it correctly. If I read the position or velocity at every servo loop at say 1ms, and my step rate is at 100khz, I must still work out the steps required between every position given at the loop rate. On 4/27/2019 12:18 PM, andy pugh wrote: On Sat, 27 Apr 2019 at 09:49, Marius Liebenberg wrote: At what rate is the velocity or position parameters of the StepGen updated? Is that rate constant? It should be the servo thread rate, and constant. ___ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
Re: [Emc-developers] Parameter update rate
On Sat, 27 Apr 2019 at 09:49, Marius Liebenberg wrote: > At what rate is the velocity or position parameters of the StepGen > updated? Is that rate constant? It should be the servo thread rate, and constant. -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1916 ___ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
[Emc-developers] Parameter update rate
Hi all At what rate is the velocity or position parameters of the StepGen updated? Is that rate constant? And is acceleration and deceleration already represented in the value? Regards Marius ___ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
