RE: What to use? EtherCAT or Ethernet Powerlink with CANopen protocol

Sorry,

Correction.

> Of course as the parallel port vanished from PCs a new 
> solution had to be
> found.  That's taken the form of either a USB or CAN bus add on module
> that then duplicates two parallel ports plus adding other automation
> features.

Should read:

> Of course as the parallel port vanished from PCs a new 
> solution had to be
> found.  That's taken the form of either a USB or Ethernet add on module
> that then duplicates two parallel ports plus adding other automation
> features.  I use the USB Smoothstepper module.


"ELS! The Solution"
Automation Artisans Inc.
http://www.autoartisans.com/ELS/
Ph. 1 250 544 4950


> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]] On 
> Behalf Of John Dammeyer
> Sent: Sunday, December 16, 2012 11:48 AM
> To: [email protected]
> Subject: RE: [CANLIST] What to use? EtherCAT or Ethernet 
> Powerlink with CANopen protocol
> 
> 
> > You're right Kees!!
> > But where can we follow with the discussion with the "field
> > buses gurus"? (I
> > will do my best. For sure!)
> > Thnaks and sorry,
> >
> >
> > Albert
> > www.inavcnc.com
> 
> Albert,
> 
> Your concept of trying to stay with CANOpen and run multiple 
> synchronized
> motors is interesting.  However, I'm not sure it's cost effective or
> feasable.  The add on card that has at least 3 CAN bus ports 
> (one for I/O
> and two for motors) can't be inexpensive.
> 
> In the hobby and small industry world there are two programs out there
> that do CNC.  One is called MACH3 and the other was called 
> EMC and runs on
> Linux.  At the start these systems controlled at most 4 motors with
> step/dir signals and the key to their functioning on a PC was the low
> level device driver interface and the parallel port.  There's a whole
> automation industry running off MACH3 and the peripherals.
> 
> Of course as the parallel port vanished from PCs a new 
> solution had to be
> found.  That's taken the form of either a USB or CAN bus add on module
> that then duplicates two parallel ports plus adding other automation
> features.
> 
> For existing users, they need only buy the add on and move 
> the parallel
> port cable from their old PC onto the add on and their CNC system
> continues as before.
> 
> The key to the system is the simple step/direction signals 
> for each motor.
> The PC application sends down blocks with an image of step or 
> not in each
> byte to be sent out by the module at 25kHz or more.
> 
> If more I/O is needed there are several companies producing MODBUS RTU
> modules that expand the I/O for limits, keypads, displays etc.
> 
> To get into simple CNC or even just a motion system for pick 
> and place for
> example, one need only buy an inexpensive set of stepper drivers, the
> motors, obviously the connecting hardware and a USB or 
> Ethernet interface.
> The CNC software is $150.
> 
> Not that I haven't considered using CAN as the backbone for running
> multiple steppers but I think the expense of intelligent 
> motors plus the
> add on card is perhaps a non-starter.  I know of one manufacturer who
> makes a stepper motor driver with CANOpen interface but position
> information is written using SDO messaging which always results in two
> messages.   One to set the Object Dictionary value and one to 
> reply that
> the value has been set.
> 
> So you are right, PDOs with the data conntaining the next position is
> required.  The code inside the motor driver has to be able to 
> interpret
> the messages quickly enough and if micro-stepping the 
> windings also handle
> everything involved in switching the current through the windings plus
> interpolating the number of steps to the next target position 
> including
> accelerations and decelerations.
> 
> Adding a CANOpen module to MACH3 or the up coming MACH4 would 
> be a useful
> endeavour over say MODIO.  Possibly using CANOpen with the 
> SYNC message
> occuring often enough to tell each motor to now impliment the 
> previously
> loaded move could work.   But you need time for ERROR FLAGs and
> retransmissions.  To design the system without room for those 
> you can run
> into trouble.
> 
> MilCAN dealt with that by banning ERROR FLAGs.  This way 
> their SYNC Frame
> from the master is guaranteed to be on time.  But what 
> happens if one of
> the move messages or position messages fails?
> 
> In the Ethernet world or even USB world the MACH3 and EMC systems send
> enough data in larger blocks and the stepping engine 
> accumulates these and
> is responsible for toggling the pins on the step and 
> direction signals to
> the motor to make them move.  But these stepping engines are FPGAs and
> everything is done in hardware.
> 
> My Electronic Lead Screw project has an LCD display, 35 
> button keypad, a
> 16 position knob encoder, beeper and a micro-stepping driver. 
>  Plus CAN
> bus.  So far I've ported the simple Microchip CANOpen stack 
> to this and
> can send an SDO to show a specfic message on the LCD screen.  
> I get PDOs
> from the button presses.  But for the stepper drive the only 
> solution I
> can see is a move to X at V with acceleration A.  Which I 
> really must get
> around to one of these days.
> 
> I think with CAN it can be done.  But not fine resolution multi-axis
> motion at a cost lower than what's already out there.  And 
> that's the key.
> At a lower cost.
> 
> John Dammeyer
> 
> 
> 
> 
> 
> "ELS! The Solution"
> Automation Artisans Inc.
> http://www.autoartisans.com/ELS/
> Ph. 1 250 544 4950
> 
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