Hello Guest it is January 28, 2020, 07:51:48 AM

Author Topic: Galil vs Vital  (Read 673 times)

0 Members and 1 Guest are viewing this topic.

Re: Galil vs Vital
« Reply #20 on: November 07, 2019, 12:31:54 PM »
Hi,
if you are going to fit encoders then fitting direct to the servo shaft is preferred as it will result in the most stable
position control loop.

What you are proposing is to fit rotary encoders so the servos may be driven by G320's which are step/direction input
drives, which are in turn commanded by an ESS/BoB as a step/direction controller ALL to avoid buying an
analogue controller?

I suspect that you are adding a great deal of complexity in the conversion for little gain. The money saved after you buy three
encoders, three G320's, an ESS and a BoB vs buying one Gallil or Hicon is likely to be small. Does that small gain cover the
added work and 'risk' of the conversion on the lines you have proposed....I'm dubious.

Craig
My wife left with my best friend...
     and I miss him!
Re: Galil vs Vital
« Reply #21 on: November 07, 2019, 05:50:20 PM »
I was just considering options and learning.  That was not a definite proposal that I had real intentions of following.
Re: Galil vs Vital
« Reply #22 on: November 07, 2019, 05:59:22 PM »
Hi,
its worth considering but I would have thought that the risk of buying all that gear only then to find out it doesn't work
or work well is a bit much. Hey, if you could buy just one drive and an encoder and experiment before spending big bucks....maybe.

Maybe someone else out there has tried such a thing. Their experience would be invaluable.

To my knowledge no-one has been able to get linear scales to work WITHOUT using an analogue controller, I could be wrong but thats
my understanding.

Craig
My wife left with my best friend...
     and I miss him!
Re: Galil vs Vital
« Reply #23 on: November 07, 2019, 07:08:25 PM »
Craig,

I thought that the main advantage of the A2 over the B2 was that the A2 could process the motor encoder and the linear encoder whereas the B2 could work with the motor encoder only.  Or did I misinterpret your earlier comments?
Re: Galil vs Vital
« Reply #24 on: November 07, 2019, 08:33:50 PM »
That is correct. It is a feature that very few use (outside of professional machine tools) but is very powerful.

This usually closes the velocity loop using the motor encoder and the position loop using the glass scales. This way you get high dynamic response with tight position control.
Re: Galil vs Vital
« Reply #25 on: November 08, 2019, 03:19:26 AM »
Hi,
one of the principles on which field oriented control rely is accurate information of the angular position of the rotor,
ergo the use of an encoder or resolver. Any flexure or backlash between the rotor and the encoder will seriously
degrade the maintenance of quadrature flux angle thereby degrading motor performance.

Field oriented control on which AC servos rely is an interesting topic, I suggest a Google search 'field oriented control by
Texas Instruments'. It will reveal a couple of excellent introductory videos on the subject. The upshot is that ALL AC servos
capable of accurate position control must have an integrally linked encoder/resolver. That does not preclude a secondary means
of detecting position but the servo drive MUST have direct access to rotor angle with zero lash/lost motion. The encoder
in the B2 series doubles as position sensor (rotational position is converted into linear position through a low lash/zero lash
ballscrew) and rotor angle for the field control loop to operate.

The A2 series is dual reading, thus it uses the encoder for field control but can 'load sense' using the auxillary encoder/linear
scale channel. Very crafty indeed. Had I realized that for as little as $50 extra each, I would have bought them instead of the B2
series examples I did get. Having said that I have no need of the 'extra fruity bits', I doubt I'll exhaust the B2 series capabilities
let alone the A2 series!!

Craig
My wife left with my best friend...
     and I miss him!