Figure 6.6-5 - Timing Diagram, Half-Stepping Motor; Figure 6.6-6 - Energizing Two Phases With Different Intensities; Figure 6.6-7 - Timing Diagram, Continuous Motion (Ideal); Figure 6.6-8 - Timing Diagram, Mini-Stepping - Newport ESP6000 User Manual

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A
B
C
D
Figure 6.6-5 — Timing Diagram, Half-Stepping Motor
Now, what happens if we energize the same two phases simultaneously but
with different currents? For example, let's say that phase A has the full
current and phase B only half. This means that phase A will pull the rotor
tooth twice as strongly as B does. The rotor tooth will stop closer to A,
somewhere between the full step and the half step positions (Figure 6.6-6).
Figure 6.6-6 — Energizing Two Phases with Different Intensities
The conclusion is that, varying the ratio between the currents of the two
phases, we can position the rotor anywhere between the two full step
locations. To do so, we need to drive the motor with analog signals, similar
to Figure 6.6-7.
Figure 6.6-7 — Timing Diagram, Continuous Motion (Ideal)
But a stepper motor should be stepping. The controller needs to move it in
certain known increments. The solution is to take the half-sine waves and
digitize them so that for every step command, the currents change to some
new pre-defined levels, causing the motor to advance one small step
(Figure 6.6-8).
Figure 6.6-8 — Timing Diagram, Mini-Stepping
1 2 3 4 5 6 7 8
A B C D A
A
B
C
D
A
B
C
D