Thanks to everybody for the information. If anything it helped me
the machine.
I tried 2 experiments to see if I could get better results.
#1. Give it 80Volts: I hooked the driver up to an 80v PS. The drive clearly
had more power, however the following error is exactly the same behavior.
#2. Run the motor with no load: I disconnected the motor drive belt.
Re-tuned the servo and then started running it in linux cnc. Net result...
exactly the same behavior.
completely linear.
So it has something to do with some sort of lag in the servo driver. I'll
be emailing leadshine with my fingers crossed hoping they can help.
than it used to.
Post by Gene HeskettPost by Curtis DuttonOk this makes sense. Thanks all for your explanations. I guess I just
wasn't sure what was reasonable behavior and what wasnt.
So if the motor is rated for 36v, and the drive is rated for 80 volts
max. How much voltage can I get away with delivering to the drives
without damaging equipment?
Thanks,
Curtis
I, as an electronics type, would look at it from the motors rated currant
viewpoint regardless of the family of motor.
The motor more than likely has permanent magnet fields, and allowing more
currant than about 1.25x the nameplate rating (based on my reading on the
subject but I don't have an URL's to offer) gets you into a magnetic
territory where the field magnets can be damaged by reducing their magnetic
strength, and its an instant and permanent effect.
The same effect applies to steppers, usually at currants above 1.25x
nameplate.
Applying an 80 volt supply to a 32 volt rated motor seems like it would be,
if not currant limited in the driver, playing with fire. I would have to
assume they said that assuming a condition where it could spin freely,
letting its counter EMF control the current and therefore the resultant
magnetic field.
This isn't normally a concern with steppers because the 10 to 30x over
voltage is just normal standard operating voltage for them. The drivers
chopper limits on the currant are many times more important to the long
term health of the motors. I see no reason not to apply much the same
thinking to PM field servo motors. Any difference is in where the magnets
are, the steppers magnet is the rotor, where a brushed servo has the magnet
in its stator. But its still the strongest magnet we know how to build in
production quantities.
Now, in servo's I'll have to plead the big dummy because in brushless, hall
effect commutated motors (BLDC?), it seem like a 3rd phase of drive to what
is basically a 3 phase wound stepper motor frame assembly, meaning the
rotor is the PM, would this not also apply?
Or do they have something even more complex for the "BLDC" format? I am
not using them, so I've not spent a lot of time researching how they are
built.
My understanding is quite incomplete for those, and is not clarified a bit
by having so many available mappings in the BLDC driver. I suspect the
reason for that boils down to a profound lack of a standard way of marking
the motors leads as to phase & polarity, making the builder try every
combination until he hits the right one that just happens to be correct for
the wire hookup sequence he used?
Is there a URL to read that would help me understand that Jon?
Post by Curtis DuttonPost by Jon ElsonPost by andy pughPost by Curtis DuttonThe motor is a 130W motor
1.5mm at around 12000mm/min.
That seems like a very small motor, and a very fast travel.
Is it possible that the motor is simply running out of steam?
Generally when the drive runs out of available voltage
the following error very suddenly grows without bound.
So, you can be at 500mm/min with error of .01mm,
and then at 550mm/min the error rises continuously
because full voltage applied to the motor is only
giving you 520mm/min, to give an example.
So, having the following error increase only a modest bit
at higher speeds may indicate the drive just has a
constant time lag in the internal loop. Or, it may
be a torque limit, where the 130 W motor is nearly
maxed out on current driving the axis at 12 m/min.
Those conditions might cause a bounded error
that increases roughly proportionally to velocity.
Jon
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