small step and then returns to its original position, ultimately
producing no revolution at all. this happens for the entire duration of
what could the reason be ?
the reply i got is :I presume you are using a small microstep size. The
magnetic pole at
the full step position you started from pulls the rotor back to that
full step position because there is not enough energy in the coils to
overcome the strong magnetic attraction at full step positions.
Microstepping at small resolutions is not a guarantee that the motor
will move a full "microstep" for each pulse issued by the controller.
Microstepping mearly provides smooth motion. You may need to issue a
few pulses before the rotor actually moves off a pole position.
Between the poles, you are more likely to see a single pulse result in
rotor movement because the energy from the pole magnets is equalized
and the stator currents are stronger. (Sine Cosine relationship is
about equal). Use larger microsteps if you want to guarantee rotor
position without an encoder. You will need to experiment on your
system to find the smallest step that will "hold" position. It may be
only in the order of 1/16 or 1/8. To hold position you need a closed
loop controller with encoder feedback. Using an encoder will also show
you how much the shaft actually moves for 1 microstep. For lower
resolutions, the step size will vary depending on how far you are from
Hope this helps.
(If you really need to position very precisely and in fine increments,
you will need to use a servo or a high mechanical ratio, which will
severely cut down on your top speed.)
My response :
Thanks a lot for the detailed reply.. my application is actually
microstepping a stepper to 128 micro steps and then converting it into
linear motion, in the order of microns. The prob i actually experienced
was : while using a stepper of 0.65 peak current and 5V dc, 1.8 degree
step angle, i could feel a jerk when pulsed for one microstep. But when
i went in for a motor of .16 peak current and 5V same 1.8 step angle,
there was an oscillation as i mentioned in my earlier query.
entire application revolves around this microstepping by a very small
step, its of great concern. please help me out.