Originally Posted by
RCaffin
Yes, you can have some instabilities if you rely solely on the linear scales for feedback. There is a bit too much delay between the motor and the carriage for this.
What you need for good results is a dual loop controller. You use the encoder on the motor to stabilise the motor (I & D), and the linear scale for position feedback (P). I have been told that Galil make such devices, but I do not know what the Galil part number is, and finding that from their web site seems very difficult.
Galil and other 'older-generation companies' do make lots of older-generation controllers designed for RS485-type control. I could not find any which offered dual loop servo control AND a Step/Dir input compatible with the likes of Mach3/4.
However, be warned: such older-generation devices are a shade more expensive than the hobby-market ones. Like OUCH.
A web search on "dual loop control" does get a number of hits. Lots of theory from various web sites, but how many real devices are available and at what prices - dunno. I have not found many, and none with Step/Dir input. But at least the concept is very well known.
Cheers
Roger