Paul Keeton wrote: >> If there's a tach on the motor, then you should be able to route that >> directly to the drive. My understanding is that some controls would >> synthesize the tach feedback from encoder feedback. If you have one of >> those, then it gets more complex (and I don't know the answer) >> > I would think that the simplest solution would be to change the motors to > tach feedback and then install either linear scales on the iron or install > encoders on the ballscrews. I would think this would be the simplest way to > handle it? > It may be, it may not be.
If there are already encoders on the motors, you should keep those installed if at all possible. PID only works well when the feedback device is rigidly coupled to the actuator - ie, when the encoder is mounted on the motor. If you use only a linear scale for feedback, and there is any backlash, then it will be difficult or impossible to tune the PID. You can use a scale in addition to an encoder, as was done on the G&L at MPM (I think there's a case study on the linuxcnc.org website, but I'm not sure where). Encoders on the screws should be OK if there's no backlash between the motor and the screw. It's a good rule of thumb to consider that every step the encoder is moved away from the motor makes PID tuning harder. - Steve ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
