Figure 6.7-6 - Dc Motor Current Driver; Figure 6.7-7 - Dc Motor Velocity Feedback Driver - Newport ESP6000 User Manual

Section 6 — Motion Control Tutorial
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control signal
±10V
Figure 6.7-6 — DC Motor Current Driver
In this case, the control signal voltage defines the motor current. The
driver constantly measures the motor current and always keeps it propor-
tional to the input voltage. This type of driver is usually preferred over the
stepper motor driver in digital control loops, offering a stiffer response and
thus reducing the dynamic following error.
But, when the highest possible performance is required, the best choice is
always the velocity feedback driver. This type of driver requires a tachom-
eter, an expensive and sometimes difficult-to-add device (Figure 6.7-7).
control signal
±10V
Figure 6.7-7 — DC Motor Velocity Feedback Driver
The tachometer, connected to the motor's rotor, outputs a voltage directly
proportional with the motor velocity. The circuit compares this voltage
with the control signal and drives the motor so that the two are always
equal. This creates a second closed loop, a velocity loop. Motions per-
formed with such a driver are very smooth at high and low speeds and
have a smaller dynamic following error.
In
M
E
M
V = velocity
T
E
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