Ok after reading a little more I guess you wouldn't need any optical
encoding with a stepper motor, that looks like a technique that only
applies to dc motors.. does that sound correct? I've been reading a
little about microstepping controllers, but have yet to determine if
stepper motors are even capable of high speed with gear reduction
used...
Stepping motors are just synchronous motors. The motor coils generate
a magnetic field that varies - more or less sinusoidally around the
circumference of the motor, and the rotor lines itself up with that
magnetic field.
If the currents through the two coils are held constant, and you try
and rotate the rotor, you will have to apply a progressively
increasing torque to move it out of alignment with that magnetic
field, up to a certain angle, where the restoring force will start
decreasing, falling to zero at twice that angle after which the rotor
will experiece an increasing force in the opposite direction, driving
it to the next stable alignment.
The peak restoring force is the drop-out torque of the stepper motor.
In a synchronous motor, you modulate the the currents through the two
coils to create a rotating magnetic field that drags the rotor around
with it. The resisitng torque that has to be overcome to allow the
rotor to rotate causes the rotor to lag the field by an angle that
depends on the ratio of the resisting torque to the drop-out torque.
When a synchronous motor is used as a stepping motor, the current
through the coils is switched on and off to create square wave
approximations the ideal sinusoidal modulation.
Microstepping drives generate stair-case approximations to the ideal
sinusoids.
http://www.cs.uiowa.edu/~jones/step/physics.html
In practice, not all stepping motors produce smooth rotation when
driven by sinusoidal fields - an early example of a 1024-microstep
microstepping drive written up in the then Journal of Physics E:
Scientific Instruments (now Mreasurment Science and Technology) ended
up being used to generate some 800 not too evenly spaced microsteps,
ESCAP still seems to sell stepping motors designed for microstepping
http://www.boxdoerfer.de/turbodsc.pdf
Getting stepping motors to rotate fast involves modulating the current
through the coils fast enough to rotate the magnetic field at the
appropriate rate, despite the inductance of the coils. This means
driving the coils with a voltage very much higher than the
manufacturers ticket voltage, which is just the rated current through
the coils multiplied by the resistance of the coils.
I've used 60V on a nominally 5V motor, and this wasn't exceptionally
high.