On Wed, 31 Oct 2012, John Kasunich wrote:
> Date: Wed, 31 Oct 2012 23:05:30 -0400
> From: John Kasunich <jmkasun...@fastmail.fm>
> Reply-To: EMC developers <emc-developers@lists.sourceforge.net>
> To: emc-developers@lists.sourceforge.net
> Subject: Re: [Emc-developers] ferror calculation incorrect in motion
>
>
>
> On Wed, Oct 31, 2012, at 10:28 PM, Peter C. Wallace wrote:
>>
>> After spending some forum time trying to help a customer with tuning a
>> torque
>> mode drive, I have noticed that ferror is calculated incorrectly and if
>> minimized will result in less than optimum actual error.
>>
>> The error appears to be that ferror is calculated before the trajectory
>> is
>> calculated so it always compares the previous waypoint with the current
>> (encoder) position.
>
> The PID loop was asked to go to the previous waypoint, and comparing
> it with the current position tells you how well it was able to achieve
> that goal.
>
> If we were to compare the encoder position with the new waypoint
> we would be evaluating the PID loop on how well it hit a target it
> hasn't even seen yet.
>
Umm no, this is simply wrong, and accounts for the difference in ferror and
pid error where none should exist
>
>
> This is easily see by the difference in ferror from
>> the
>> PID error (they should be the same)
>>
>> This causes a value equal to the velocity in machine units per
>> second*servo
>> thread_period to be added to the ferror.
>>
>>
>>
>> Peter Wallace
>> Mesa Electronics
>>
>> (\__/)
>> (='.'=) This is Bunny. Copy and paste bunny into your
>> (")_(") signature to help him gain world domination.
>>
>>
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>
>
> --
> John Kasunich
> jmkasun...@fastmail.fm
>
> ------------------------------------------------------------------------------
> Everyone hates slow websites. So do we.
> Make your web apps faster with AppDynamics
> Download AppDynamics Lite for free today:
> http://p.sf.net/sfu/appdyn_sfd2d_oct
> _______________________________________________
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> Emc-developers@lists.sourceforge.net
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>
Peter Wallace
Mesa Electronics
(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.
------------------------------------------------------------------------------
Everyone hates slow websites. So do we.
Make your web apps faster with AppDynamics
Download AppDynamics Lite for free today:
http://p.sf.net/sfu/appdyn_sfd2d_oct
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