On 01/27/2021 11:35 AM, Todd Zuercher wrote:
How useable are Fanuc's servos and amps with Linuxcnc? My understanding is
that it is very involved to try to force them to work with anything other than
a Fanuc control
I make converters for the two most common types of Fanuc
encoders used on brushless motors.
I also make a digital servo amp for them that can be used
with my PWM controller.
The older "red cap" motors had encoders with standard
quadrature plus index output, but the commutation signal was
proprietary. I have a board that converts the commutation
to industry-compatible "Hall" signals.
The newer type is serial, but my converter produces
industry-compatible quadrature plus index, plus the "Hall"
signals. Note there are absolute and incremental versions of
these encoders.
The problem with the incremental versions, like (alpha)I64,
is that they are lost when power is applied, so they need
you to crank the motor past the index location by hand after
every power on, before commutation is available. So, these
encoders need power-off brakes and battery backup if the
control is ever turned off.
The absolute version have additional low-res data tracks
that allow the encoder to know the angle immediately at
power-on, so no battery is needed to have commutation
immediately on power on.
Now, the Fanuc servo amps are more difficult, as about 1984
they stopped releasing any documentation on their
electronics. So, it is essentially impossible to find any
schematics or connection info for their amps. Most of the
brushless amps take SIX PWM signals per axis, so
the controller sends separate PWM to EACH transistor. This
moves all the smarts to the controller, but it complicates
things a bit.
Jon
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