Brian wrote: > I have a setup problem that I think should be a fairly common issue > that I would like to bring up to the development team. > > I have a milling machine that uses open loop steppers to operate the > screws, and scales to monitor table position. I want to use the > scales to monitor the table position when the drives are disabled, and > I am manually moving the machine. This will mitigate the need for an > MPG. > > My problem is, I don't see a good way to integrate the direct > reading scales into the HAL component 'axis'. I can't use > motor-pos-fb, because the backlash is added to it to determine actual > joint position. > You can do this with the hardware step generators available with EMC. They work like a servo, even when the steppers are run open-loop. Axis commands a velocity in steps/second, and the step generator puts out that rate. The steps are counted by an encoder counter and fed back to the PID component and the axis component. You can see the logic in your configs/univstep directory. If you flip a switch on the Universal Stepper Controller, it switches to reading an actual encoder and ignores the exact number of steps sent. This allows mixing open- and closed-loop steppers in the same system, too.
Jon ------------------------------------------------------------------------------ This SF.net email is sponsored by Make an app they can't live without Enter the BlackBerry Developer Challenge http://p.sf.net/sfu/RIM-dev2dev _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
