Dynomotion

Group: DynoMotion Message: 9255 From: gzuro Date: 2/24/2014
Subject: convert to closed loop to kflop with servos
Hi,

I have an old DynaCNC router table that is set up with Mach and G320s (and a variation of the MP1000 from C&CNC).  I've been using a kflop on a couple of other stepper systems and would like to convert this servo system to use it as well.

I am trying to figure out how to close the loop back to the kflop.  I came across this thread which seems to express my thoughts pretty well:


, but I am at my limit of experience/understanding so would appreciate some guidance regarding what sort of drive might be used in place of the G320s and whether the kanalog is a necessary component.

I am somewhat more specifically interested in a more detailed description of this configuration (by TomK):

"
There is a clear advantage to have the feedback connected back to the controller. This allows the controller to track position during a fault or amplifier disable. Without feedback after a fault the drive might still know the axis position but the controller won't. So you will need to always re-home.

With feedback to the controller, the controller will be aware of the current following error. It can then fault on excessive following error without the need of bringing extra status in from the drive.
"

Thanks,
Greg
Group: DynoMotion Message: 9256 From: Tom Kerekes Date: 2/24/2014
Subject: Re: convert to closed loop to kflop with servos
Hi Greg,

One option would be to just keep the G320s let them close the loop as they are now and command Step/Direction to the G320s.  But as I attempted to describe in that quote in this type of configuration things are open loop from the Controller's (KFLOP's) perspective.

To have KFLOP close the position loop some type of DC Brush Motor Amplifier is required.  A SnapAmps can drive up to 4 Brush Motors.  You didn't include any info on your motor requirements.  Otherwise you might use something like an a-m-c.com type of analog amplifier.  In that case Kanalog would be required to command the amplifier with +/-10V analog command signals.  Encoder signals must provide position feedback back to KFLOP.  If your encoders have differential outputs they can be connected to Kanalog or SnapAmp.  Differential signals are preferable because of less noise sensitivity.  G320's only have single ended encoder inputs (I believe).  3rd party adapters are available.  See:

http://dynomotion.com/faq.html#Encoders

HTH
Regards
TK


Group: DynoMotion Message: 9257 From: gzuro Date: 2/24/2014
Subject: Re: convert to closed loop to kflop with servos
Hi Tom,

I think that I have a good handle on the drive-the-G320s-from-kflop option, so I'd like to pursue the second option.

The motors are Moog C34-L80 units which have a rated power of 110W.  So it looks like the SnapAmp is fine in that regard.

Assuming that's the case, I infer from your next statement that a KAnalog would not be required.  In this case, how is the motor speed direction specified to the SnapAmp (what would be the -10 to +10V signal in the KAnalog + a-m-c scenario)?
The encoder says: "Gnd, Index, Ch. A, +5v, Ch. B" .  So it looks like I need a few of the adapters.

Is there anything else that I'm missing?

Thanks!






---In DynoMotion@yahoogroups.com, <tk@...> wrote:

Hi Greg,

One option would be to just keep the G320s let them close the loop as they are now and command Step/Direction to the G320s.  But as I attempted to describe in that quote in this type of configuration things are open loop from the Controller's (KFLOP's) perspective.

To have KFLOP close the position loop some type of DC Brush Motor Amplifier is required.  A SnapAmps can drive up to 4 Brush Motors.  You didn't include any info on your motor requirements.  Otherwise you might use something like an a-m-c.com type of analog amplifier.  In that case Kanalog would be required to command the amplifier with +/-10V analog command signals.  Encoder signals must provide position feedback back to KFLOP.  If your encoders have differential outputs they can be connected to Kanalog or SnapAmp.  Differential signals are preferable because of less noise sensitivity.  G320's only have single ended encoder inputs (I believe).  3rd party adapters are available.  See:

http://dynomotion.com/faq.html#Encoders

HTH
Regards
TK


Group: DynoMotion Message: 9258 From: gzuro Date: 2/24/2014
Subject: Re: convert to closed loop to kflop with servos
Tom,

Could I close the loop via the KFlop's single ended encoder inputs while driving via the SnapAmp?

Thanks,
Greg
Group: DynoMotion Message: 9259 From: Tom Kerekes Date: 2/24/2014
Subject: Re: convert to closed loop to kflop with servos
Hi Greg,

With SnapAmp the desired motor current is commanded digitally from KFLOP.   There is no need for an analog signal.

Yes the encoders are only single ended.  You could add differential drivers or connect to the single ended KFLOP encoder inputs.  Single ended signals are much more noise sensitive so if you decided to go that way try to have shielding on both the motor wiring and the encoder cables.

Regards
TK

Group: DynoMotion Message: 9260 From: gzuro Date: 2/24/2014
Subject: Re: convert to closed loop to kflop with servos
Tom, Thanks for the clear description of my options. I will plan on double ended to the encoder. I don't want to waste time on the alternative. Cheers, Greg