mesa hw for cnc mill retrofit
24 Feb 2013 09:20 #30508
by blesbok19
mesa hw for cnc mill retrofit was created by blesbok19
Hello,
I'm considering the combination of 7I80 + 7I77 + softdmc for a cnc mill
retrofit. My servo drives accept analog (torque) commands and provide
quadrature encoder position feedback. Does this combination of mesa
cards seem like a reasonable choice? Is the softdmc firmware supported
for this device under linuxcnc? I've looked over the "host2mot"
firmware and it appears there a pre-built bitfiles for common
configurations. Is the same true for softdmc? Can I download the
softdmc source?
Also, I'm considering another option using mesa accessories (7I77) with
softdmc on my own fpga board. Do you foresee significant difficulties
building this firmware for virtex5, specifically lx50 or lx85? I
suspect these have more than adequate resources.
Thanks for your help,
Brent
I'm considering the combination of 7I80 + 7I77 + softdmc for a cnc mill
retrofit. My servo drives accept analog (torque) commands and provide
quadrature encoder position feedback. Does this combination of mesa
cards seem like a reasonable choice? Is the softdmc firmware supported
for this device under linuxcnc? I've looked over the "host2mot"
firmware and it appears there a pre-built bitfiles for common
configurations. Is the same true for softdmc? Can I download the
softdmc source?
Also, I'm considering another option using mesa accessories (7I77) with
softdmc on my own fpga board. Do you foresee significant difficulties
building this firmware for virtex5, specifically lx50 or lx85? I
suspect these have more than adequate resources.
Thanks for your help,
Brent
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24 Feb 2013 10:16 #30510
by PCW
Replied by PCW on topic mesa hw for cnc mill retrofit
SoftDMC is not supported by LinuxCNC, only HostMot2.
Also the 7I80 is not supported yet by LinuxCNC (and will require the Xenomai branch)
For a 7I77, the 5I25 (or 6I25) is the easiest currently supported option.
HostMot2 is pretty easy to build on almost any Xilinx FPGA from Spartan II up
SoftDMC V4 is a pain to build and quite inflexible. V5 is being worked on now
and will be much more flexible. We may consider LinuxCNC support for V5.
Also the 7I80 is not supported yet by LinuxCNC (and will require the Xenomai branch)
For a 7I77, the 5I25 (or 6I25) is the easiest currently supported option.
HostMot2 is pretty easy to build on almost any Xilinx FPGA from Spartan II up
SoftDMC V4 is a pain to build and quite inflexible. V5 is being worked on now
and will be much more flexible. We may consider LinuxCNC support for V5.
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25 Feb 2013 10:55 #30545
by blesbok19
Replied by blesbok19 on topic mesa hw for cnc mill retrofit
Thanks for the quick response.
It looks like the 7I77 plus a pci/pcie board may be my route. It's my understanding the hostmot2 firmware handles high speed tasks like communicating with DACs, encoder counting, etc in hardware and relatively lower speed operations like the servo loop, spline, trajectory, etc in the host.
If I was stuck on the idea of hw based control, what are my options for application software? Mach? Something else? I looked over the softdmc manual and get the gist of it. Is there any higher level driver or just a register interface?
Cheers,
Brent
It looks like the 7I77 plus a pci/pcie board may be my route. It's my understanding the hostmot2 firmware handles high speed tasks like communicating with DACs, encoder counting, etc in hardware and relatively lower speed operations like the servo loop, spline, trajectory, etc in the host.
If I was stuck on the idea of hw based control, what are my options for application software? Mach? Something else? I looked over the softdmc manual and get the gist of it. Is there any higher level driver or just a register interface?
Cheers,
Brent
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25 Feb 2013 21:38 #30559
by andypugh
Dynomotion have all-hardware solutions for motion control too: dynomotion.com/index.htm
The problem with the hardware systems is that you only get the features that the hardware manufacturer puts there. The classic example here is G76 threading. That was added to LinuxCNC, and everybody got it in the next release. If the motion control was all in hardware, then they wouldn't have it.
I personally think that the current task-split between LinuxCNC and the Mesa/Pico/Motenc/Other hardware is approximately optimal.
Replied by andypugh on topic mesa hw for cnc mill retrofit
Yes, that is correct. Having the computationally-intensive stuff on the host PC (which has a hugely powerful CPU) makes quite a lot of sense, and also allows you to see what is going on, and make realtime changes. Halscope, for example, lets you plot exactly what is happening in the HAL layer. This is immensely useful and would be very difficult to do with a fully-hardware system.It looks like the 7I77 plus a pci/pcie board may be my route. It's my understanding the hostmot2 firmware handles high speed tasks like communicating with DACs, encoder counting, etc in hardware and relatively lower speed operations like the servo loop, spline, trajectory, etc in the host.
Maybe Mach. The Smoothstepper seems to move much of the motion task into hardware.If I was stuck on the idea of hw based control, what are my options for application software? Mach? Something else?
Dynomotion have all-hardware solutions for motion control too: dynomotion.com/index.htm
The problem with the hardware systems is that you only get the features that the hardware manufacturer puts there. The classic example here is G76 threading. That was added to LinuxCNC, and everybody got it in the next release. If the motion control was all in hardware, then they wouldn't have it.
I personally think that the current task-split between LinuxCNC and the Mesa/Pico/Motenc/Other hardware is approximately optimal.
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26 Feb 2013 07:54 #30582
by blesbok19
Replied by blesbok19 on topic mesa hw for cnc mill retrofit
I'm not married to an all hw solution, it's just what I'm most accustomed to. After diving further into the documentation and forums, I am warming up to linuxcnc. The HAL documentation is very helpful.
The drives I'm using (Fanuc SL series) accept torque or velocity commands (analog) or position (step/dir). When I tested these previously in each mode, I kinda expected the drive's built in controller to perform best (matched motor/drive pair) but actually got better tuning results in torque mode using an external controller. Of course the external controller had a 16kHz servo loop, fast DACs, etc. Could I expect similar performance at lower linuxcnc loop rates, or would the scales tip in favor of using velocity or position mode?
The drives I'm using (Fanuc SL series) accept torque or velocity commands (analog) or position (step/dir). When I tested these previously in each mode, I kinda expected the drive's built in controller to perform best (matched motor/drive pair) but actually got better tuning results in torque mode using an external controller. Of course the external controller had a 16kHz servo loop, fast DACs, etc. Could I expect similar performance at lower linuxcnc loop rates, or would the scales tip in favor of using velocity or position mode?
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26 Feb 2013 09:29 #30589
by PCW
Replied by PCW on topic mesa hw for cnc mill retrofit
I would suggest using velocity mode since I would expect that LinucCNC would be limited to about a 4- 6 KHZ maximum thread rate
usually 1KHz or so is fine for CNC type machine position control loops where the velocity portion is handled by the drive
(and the mechanical bandwidth of the machine is usually less than 50 Hz)
usually 1KHz or so is fine for CNC type machine position control loops where the velocity portion is handled by the drive
(and the mechanical bandwidth of the machine is usually less than 50 Hz)
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