On Sun, 22 Apr 2012, Andrew wrote:
Date: Sun, 22 Apr 2012 22:05:28 +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
22 ???????????? 2012 ??. 19:04 Peter C. Wallace <p...@mesanet.com>
??????????????:
What are your tuning values? looks like some of the error could be tuned
out with FF1
I noticed that too... after the screenshot was sent.
Is the following correct?
FF0 - velocity
FF1 - acceleration
FF2 - jerk
off by one... for a position loop FF1 (1st derivative) is velocity feed
forward and FF2 (second derivative) is acceleration feed forward.
That is FF0 can fight f-error at high speed, FF1 when
accelerating/decelerating, FF2 helps eliminate transien peaks?
How do I use torque PID? Does it make sense here?
Encoder velocity is calculated each servo period, isn't it? Then I guess D
noise is caused by 5um encoder, each 5um step results in certain
velocity
peak (5um/250us servo period=0.02m/s) which cause compensatory move and so
on. Strange, but increasing servo period can decrease noise too? Anyways,
next time I use 1um and it should decrease noise 5 times.
Probably not 5 times:
When the encoder velocity estimation is used it is not as affected by
encoder resolution as the normal D/DT of position. This is because the velocty
estimation measures counts/delta_time rather than count per servo period. the
delta_time being measured by time stamping encoder signal edges with a 1 Usec
resolution clock. The velocity estimation is still affected by quadrature
error (deviation from exact 90 degree phase shift between A and B) so if this
can be improved (some encoders have gain pots on the A and B photodiode amps)
I will continue tuning later today, now installing all motors. And the
encoder signals still can't pass through 7i39. Can it be some levels
incompatibility?
No idea we have >500 7I39s in the field and none have exhibited this
characteristic. I would trace the encoder signal. If the cable has been Ohmmed
out, only thing I can think of off hand is a damaged 74HCT14 (it has a1 K
series resistor on the input so it would need >15V to cause damage)
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For Developers, A Lot Can Happen In A Second.
Boundary is the first to Know...and Tell You.
Monitor Your Applications in Ultra-Fine Resolution. Try it FREE!
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