Hi,

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>> The big problems that I would see trying to do this with a PLC would be speed and latency. <<

> Indeed! We would need counter cards which store their value at a trigger, so all counters can be read buffered afterward. National Instruments has such cards (e.g. NI 6602) but I have no experience with PLC equivalents. <

Please have a look to the remote I/O modules offered for different fieldbus systems. For PROFIBUS e.g there are a lot of vendors offering a bunch of different counter modules. This is also the case for other types of interfaces.

Best Regards,
Armin Steinhoff

 

Hello,

The reason I recommended the Delta Tau unit is that it already has the hard real time multi-threaded computing engine (Their old product or the new one), and a very sophisticated set of software with the hardware already integrated. I think if you are doing anything more complicated than sending low speed position updates that a motion controller is more appropriate. The other nice things about a real motion controller is that you have motor tuning and plotting tools available, as well as not needing to write any driver code for the RTOS.

M. Griffin Wrote:
> One sort of solution that you might look at is a PC/104
> system with either real-time Linux or QNX. That is probably
> the closest off the shelf thing to your existing Transputer
> system. Alternative hardware could be a mini-itx board, but
> the expansion options for those are limited (typically only 1 slot).

 

> Hmm I will look for alternatives but I'm a bit surprised, because the general NI-DAQmx LabVIEW driver seems like such a nice and well maintained piece of software (and I've heard lots of positive comments about it, also regarding future compatibility). <

If you've heard good things about LabView doing motion control well... it wasn't from anyone who has done a serious application in motion control...sorry, that's just they way it is.

 

I just want to confirm what others have brought up -- that is, the ability to average multiple encoders for use as feedback is a standard feature of our controllers. No programming is required to implement this features, just the proper setting of some setup variables. The summing will be performed in hard real time every servo period, and will take well under a microsecond to complete.

Curt Wilson
Delta Tau Data Systems

 

The Delta Tau unit probably would be a solution, but then you have the whole spectrum of closed source, proprietary problems that come along. Single source for tools, software, support, everything. Long term, proprietary vendors tend to move on and lose interest in your moment in time. For long lived solutions like this, Open Source and commodity hardware offer a higher degree of protection against obsolescence. Not necessarily criticism, they know what they're doing and if you need their expertise, that's how you pay for it. But a highly technical customer group might appreciate the difference. It's not like automating a chicken plant.

Regards,
cww

 

TA> If you've heard good things about LabView doing motion control
TA> well... it wasn't from anyone who has done a serious application
TA> in motion control...sorry, that's just they way it is.

http://www.google.com/search?q=CNC+LabVIEW

BTW, what do you mean when speak about serious motion application? In
the task we have just several independent axes. Modern approach in
motion control is just motor+driver, have a look at:

http://imshome.com/products/mdriveplus_overview.html

Send command and get fun. In the worst case it is remote DAC +
coordinate (remote quadrature counter) with necessity to form the
trapezoidal path. I see no problem (of course, if you do not insist
program it with IEC's LD ;-).

--
Best regards,
Vladimir E. Zyubin

 

> serious motion application? In the task we have just several independent axes. Modern approach in motion control is just motor+driver, have a look at: <

Thanks for helping me prove my point... several independent axes... doesn't seem to be much of a serious motion application... and yes integrated motor/drives are becoming more common.