minimize any discrepancy between a
desired and an actual position.
In actuality, a simple DC motor
servo loop would have been the ideal
approach using a DC motor with
position feedback. However, the
unique servo loop in Figure 3 was
implemented making use of a stepper
motor in lieu of a DC motor, and vastly
improved tracking performance using
the same motor, was less complex, and
Figure 3. DC servo block diagram using a stepper motor.
Circuitry for a
DC Servo Using a
Figure 4 shows the electronic
circuitry needed to implement the
simple positioning servo using a
stepper motor instead of a DC motor.
Figure 5. Summing electronics.
Figure 4. Circuitry required to implement the “DC Servo.”
SERVO 12.2012 69