Hi Dan! On 07.02.2016 18:06, Dan Bloomquist wrote: > [...] > > > What is different is that it their mill positions with motor encoders. > My mill has tachs on the motors and glass scales. I haven't put a scope > on the glass but judging from the wires, they are quadrature. I can't > imagine how it would work if they were not. From what I can find making > this work takes a bit of thought. It is not as simple as using motor > encoders directly. So, my first question would be, 'has anyone here done > a conversion like this?' I'm guessing there will be a set of Mesa boards > that can handle this job and if someone has done this, that is what they > used.
Lacking a lot of experience, I can't tell you exactly what to do, but I'd go for a cascaded controller loop architecture: The inner loop is for velocity and takes feedback from the tachs, while the outer (slower) loop controls position by means of the scale feedback. Depending on the stiffness of the drive train (are there belts or gears between motor and screw?), you could possibly also get away without using the tachs at all, by simply calculating the current velocity out of the scale feedbacks. This would then give you about the same setup as in the SheetCake project. Doing this should be quite straightforward, using hardware from Mesa or from some other supplier, as long as LinuxCNC provides reasonable support for it. Bye, Philipp
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