On Sun, 22 Apr 2012, Andrew wrote:
Date: Sun, 22 Apr 2012 00:42:18 +0300
From: Andrew <parallel.kinemat...@gmail.com>
Reply-To: "Enhanced Machine Controller (EMC)"
<emc-users@lists.sourceforge.net>
To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
Subject: Re: [Emc-users] BLDC on 7i43 + 7i39 + linear motors
21 ???????????? 2012 ??. 23:04 Peter C. Wallace <p...@mesanet.com>
??????????????:
might try inverting the sign on your encoder scale (or bldc scale
I already did that, with no success. But out af a sudden it works
now. Though still unstable.
Now tuning PID.
What is minimum servo period for 7i43? I set 500000 and it became much more
stable.
Minimum period depends on how many I/O cycles you do and how much of the host
cycles you are willing to burn up doing I/O. with the parallel ports I've
tested with, I get between 3-6 Usec of I/O time for each 32 bit register
read/write on the EPP interfaced 7I43. So a three axis system may have about
18-20 I/O cycles you would use about 54 to 120 usec of host time doing EPP I/O
for a simple 3 or 4 axis system 4KHz may be possible (note: the 7I43 is the
slowest FPGA card we make due to the EPP interface ~8-12 times slower than the
PCI cards)
Tuning a voltage mode (or current mode = torque mode) drive is tricky you will
need a fair amount of P and D and FF1. The higher the sample rate the better
for phase margin (which will allow high stable gain). Also tuning should be
done with the carriage loaded and FF1 especially should be tuned with the
final motor voltage as FF1 is motor voltage dependent on a a voltage mode
drive
Peter Wallace
Mesa Electronics
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