Stepper Motors

[AdamHeard]

Originally Posted by GeeTwo

I agree. Maybe I've led a sheltered life, but the only project anyone ever discussed with me that included steppers was ca. 1983 when the University of New Orleans automated the aiming of their 8" telescope. (With the light pollution, it had at least twice the light-gathering capability that could be justified. At least until 2005, when the lights went out for most of a year.) I can also imagine steppers being useful in machining applications. I really cannot come up with an on-field FRC application for a stepper that would not be more robustly met with a brushed motor and a high-count encoder.


On another subject I saw earlier in this thread: I have never paid much attention to brushless DC motors, except to plug a COTS fan into a computer I was building, the high-level theory as I was taking undergrad E&M, and a bit of subliminal/hindbrain work as I was reading "Prodigal Genius" about ten years ago. I was rather surprised to read that brushless motors could be left in a state that could not be electrically escaped. It seems to me that brushless motors should be built with N magnets on the rotor and N-1 electronically cycled coils on the frame/stator (or N+1 on the stator, but I prefer that the simpler solution be on the active side). In either of these configurations (assuming the smaller number is at least two), there would be no "trapped" states from which the motor could not start; essentially half of the coils would be available to pull the shaft around at any position. Did I miss a trick, or did the designers of brushless motors?

This is one the reasons why the motors have multiple (most commonly three) phases. All typical industrial servo motors will be able to generate torque at any shaft angle.