Dynomotion

Group: DynoMotion Message: 5513 From: darrengladysz Date: 8/3/2012
Subject: Step Direction or Analog +10v/-10v
Hi,

I just purchased a kflop and kanalog. I am going to be using this on a cnc router for wood that is on its way from China (similar to this http://www.omni-cnc.com/products/auto_tool_changer_cnc_router/cnc_router_OR1530LATC.html but I chose to use a kflop controller instead).

I have four 1.5kw Delta drives and a vfd. The Delta drives are digital drives and offer the choice of step/direction or analog input signals (velocity mode not torque). The drives also have all the software required for the pid loop.

I am at the point where I have to decide the input signal I will feed to the drives. Either step/direction or an analog +10v/-10v.

I was wondering which method was better and why and even if there is a difference or rather a significant difference. I presume analog is more precise providing everything is well shielded as it is easier to vary the input voltage signal rather than a pulse frequency but wanted to get input from other users. Also, analog most likely gives a more fluid motion profile again due to the fact that it is easier to vary the voltage than the frequency, a the frequency variations may look like steps rather than a smooth curve, although there should be ample leeway as the frequency is most likely many times lower than the dsp oscillator clock.

The other issue I was curious about was about having two pid loops. One on the drive and one on the kflop. Is there any special precautions to take to avoid a battle between the two loops? Specially when adding feedforward velocity and other tuning parameters?

Thank you

Darren
Group: DynoMotion Message: 5516 From: Tom Kerekes Date: 8/5/2012
Subject: Re: Step Direction or Analog +10v/-10v
Hi Darren,

It should work either way.  It mainly depends on whether you feel more comfortable closing the position loop in your Amplifier or in KFLOP.  We prefer using +/-10V analog and closing the loop in KFLOP.  As you mentioned this also keeps the trajectory as floating point numbers inside KFLOP rather than Integer Steps sent to the drive.

Regards
TK

Group: DynoMotion Message: 5517 From: darrengladysz Date: 8/5/2012
Subject: Re: Step Direction or Analog +10v/-10v
Thank you Tom.

--- In DynoMotion@yahoogroups.com, Tom Kerekes <tk@...> wrote:
>
> Hi Darren,
>
> It should work either way.  It mainly depends on whether you feel more comfortable closing the position loop in your Amplifier or in KFLOP.  We prefer using +/-10V analog and closing the loop in KFLOP.  As you mentioned this also keeps the trajectory as floating point numbers inside KFLOP rather than Integer Steps sent to the drive.
>
>
> Regards
> TK
>
>
>
> ________________________________
> From: darrengladysz <dgladysz@...>
> To: DynoMotion@yahoogroups.com
> Sent: Friday, August 3, 2012 11:21 PM
> Subject: [DynoMotion] Step Direction or Analog +10v/-10v
>
>
>  
> Hi,
>
> I just purchased a kflop and kanalog. I am going to be using this on a cnc router for wood that is on its way from China (similar to this http://www.omni-cnc.com/products/auto_tool_changer_cnc_router/cnc_router_OR1530LATC.html but I chose to use a kflop controller instead).
>
> I have four 1.5kw Delta drives and a vfd. The Delta drives are digital drives and offer the choice of step/direction or analog input signals (velocity mode not torque). The drives also have all the software required for the pid loop.
>
> I am at the point where I have to decide the input signal I will feed to the drives. Either step/direction or an analog +10v/-10v.
>
> I was wondering which method was better and why and even if there is a difference or rather a significant difference. I presume analog is more precise providing everything is well shielded as it is easier to vary the input voltage signal rather than a pulse frequency but wanted to get input from other users. Also, analog most likely gives a more fluid motion profile again due to the fact that it is easier to vary the voltage than the frequency, a the frequency variations may look like steps rather than a smooth curve, although there should be ample leeway as the frequency is most likely many times lower than the dsp oscillator clock.
>
> The other issue I was curious about was about having two pid loops. One on the drive and one on the kflop. Is there any special precautions to take to avoid a battle between the two loops? Specially when adding feedforward velocity and other tuning parameters?
>
> Thank you
>
> Darren
>