Hi,
but with these Kollmorgen AKM servos, can they work properly without the encoder signals connecting back to the S200 drivers?
I'm not familiar with Kollmorgen servos, my experience is with Allen Bradley servos. I suspect that the servos would not, in fact
could not operate without the encoders connected and working.
Leave aside for the moment that how would the drive know when to commutate the stator windings but without the encoder the
drive has no means to determine the rotor position so it cannot then calculate the phase currents necessary to produce
a stator field in phase quadrature to the rotor and produce torque thereby.
It is absolutely fundamental to Field Oriented Control AC servos that the rotor position is known to the drive, be it an encoder
or a resolver. Without rotor position there can be no quadrature stator field. Texas Instruments do a truly excellent
video on Field Oriented Control.
https://www.youtube.com/watch?v=cdiZUszYLiAModern servos ABSOLUTELY require a matching drive. As such the motion controller can just be open loop step/direction,
it need not be a feedback controller. The servo and servo drive manufacturer does a superb job of matching the servo
and drive feedback loop. In all fairness they do a better job of it than you or I can do and exceed the capabilities of even
top motion controllers like Gallil.
My Allen Bradley servo for instance has thermal parameters such that the drive can model the thermal performance of the
servo. Even more amazingly the servo has piecewise linear magnetic coefficients so the drive can model magnetic saturation
effects which incidentally feed into the thermal model. Such sophistication of thermal and magnetic modeling is
just that much more advanced than any motion controller.
The trend in CNC is that servo and servo drives are getting smarter and smarter.
Once upon a time servo drives were just amplifiers. The motion controller monitored the encoder/resolver; enacted the
feedback loop and outputted a precision analogue voltage to the servo amplifier. The servo drive was dumb, or maybe had
a velocity feedback loop at best.
More recently servo drive itself monitors the encoder/resolver, enacts the feedback loop and drives the servo directly. The motion
controller need only be open loop step/direction type. Think Mach3 and Mach4. The servo drive now has all the feedback
tuning including the thermal and magnetic modeling I've already mentioned. The servo drive is smart.
More recently still with Ethercat, Profinet, CANOpen and others the servo drives are becoming motion controllers in their
own right. Thus you don't have a motion controller at all, your PC becomes the trajectory planner and is the
Ethercat master while each of the Ethercat slaves (each servo drive) does it own motion control. This is called 'distributed
motion control'. It IS THE COMING THING. The servo drive is now smarter than the controller!
When you log onto the Mach forum you may have noticed a video of a Matsura VMC doing a job. What you may not have noticed is
the Mach4 is the trajectory planner with KingStar/Interval Zero RTX64 providing the software to make Mach4 and the PC
an Ethercat master. So that Matsura is running
WITHOUT A MOTION CONTROLLER!!!The days of sophisticated feedback controllers like Hicon and Galill are numbered, why would you bother with expensive
realtime hardware when you just need a little extra software and some Ethercat capable servos?
As I said, the trend is for servo drives to get smarter and smarter......what happens next???
Craig