On Thu, 2008-07-03 at 00:21 -0400, Olivier Henley wrote: > Hi to all, > > My question is concerning motor controllers. For my own good reasons, I don't > want to buy a commercial controller, but design it myself using material, > information I found in scientific literature and, of course, internet. > > With all the design propositions I studied, I need confirmations about a > roadmap, I believe, possible. Let's say a dc drive. > > EMC2 offering real-time capabilities (real-time kernel), can it send PWM > (pulse > width modulation) to a H-bridge drive using PWMgen, receive counts from a quad > encoder and calculate a PID controller to modify the next outgoing PWM. One > channel of output (PWM), one channel of input (encoder) and compensation > calculations (PID) in pc. > > What about cpu overload, how many axes do you think a recent pc could handle > this way, what about latency, does the communication protocol between the pc > and the controller is critical? > > If this configuration is possible, I think the controller becomes much easier > to > build. A H-bridge, an analogue current limiter (shunt resistor), filtering > and/or isolation of signals, and if I don't forget a main feature, that's > about > it... > > Last question. What would be the best tool to handle the quad encoder input > signal? Is there a pretty close HAL setup I should look at to hack in case my > setup would be viable? > > Thanks in advance, > > Olivier H.
EMC2 has most of what need, built in. It translates motion commands (g-code) into axis (joint actually,) outputs with the option of modifying the output based on feed-back. EMC2 has a quadrature encoder input module as well as a PWM output module that uses the parallel port. EMC's structure is described here: http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?EMC_Components In this diagram: http://wiki.linuxcnc.org/uploads/EMC_Control_LG.gif everything except the encoder, motor, power amp and limit switches is in EMC. A simple example is here: http://emergent.unpythonic.net/projects/01142347802 You can get reasonable performance in a larger machine by just scaling this system up. For high speeds and/or high resolution the parallel port will not be able to keep up, so a parallel port or PCI/ISA based controller with fast encoder counters and signal generators can be used, but the basics are the same. See here for hardware that works with EMC: http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?EMC2_Supported_Hardware The above is over simplified, but may help get you started. -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC/EMC CNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending Craftsman AA 109 restoration Shizuoka ST-N/EMC CNC) ------------------------------------------------------------------------- Sponsored by: SourceForge.net Community Choice Awards: VOTE NOW! Studies have shown that voting for your favorite open source project, along with a healthy diet, reduces your potential for chronic lameness and boredom. Vote Now at http://www.sourceforge.net/community/cca08 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
