craig wrote: > > What useful information can be extracted from sensing stepper voltage > and current responses? > > Mariss Freimanis of Gecko did quite a bit of work on this a while ago, called the "unstallable stepper", I think. There should still be some info on the Geckodrives web site about it. The problem, of course, is if one motor slows down to prevent a stall, all the other motors need to also slow down by the same amount, or you still make a mess of the part. I think this is where Mariss fell down, as he didn't have a sensible way for the drive to report what it was doing back to a CNC control with software-generated steps out the parallel port. > Are there useful differences in the waveforms for missing steps? nearly > missing steps? > Once you've missed a step, all is lost as the stall is in progress. What Mariss was doing was measuring the phase angle between current and voltage, and he could keep the stator pole just less than 90 degrees ahead of the rotor pole, to develop maximum torque. When the phase angle exceeded this, you had to back off or move into the stall territory.
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