On 03/25/2015 09:59 PM, Leonardo Marsaglia wrote: > 2015-03-25 23:17 GMT-03:00 Jon Elson <el...@pico-systems.com>: > >> You should check this out : >> >> http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Combining_Two_Feedback_Devices_On_One_Axis >> >> There used to be a web page that described dual feedback on >> one of the big machines at Stuart Stevenson's MPM shop and >> had a bit of history of how they arranged to do that, but I >> can not find it now. They used a linear encoder for position >> feedback and a shaft encoder on the motor for velocity feedback. >> >> (Anybody know where the descriptive page with photos, etc. >> on that has gone to?) >> > Hello Jon and thanks for the link I didn't remember about it. > > I guess my approach of using the same encoder mounted on the shaft of the > motor isn't the best solution for speed and position feedback right?. No, nothing wrong with it, if you have sufficient encoder counters. > As I told gene I was planning on using the same encoder for velocity and > then position feedback but I don't know if this is a good option. Do you mean to extract velocity from the encoder and then feed it out a DAC channel to a velocity servo amp? This is what almost all FANUC controls do, and a few people are doing this with LinuxCNC. I think Chris Radek is doing this on his machine, and John Kasunich and Chris Kelley at Tx/Rx Labs in Texas got this working on their PowerHawk mill.
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