Newport ESP300 Series, Руководство пользователя, Страница: 267 / 314

This type of driver is used mostly in low cost applications where
following error is not a great concern. The controller does all the work
in trying to minimize the following error but load variations make this
task very difficult.
The second type of DC motor driver is the current driver, also called a
torque driver (
Figure 5.50 ).
In this case, the control signal voltage defines the motor current. The
driver constantly measures the motor current and always keeps it
proportional to the input voltage. This type of driver is usually
preferred over the previous one in digital control loops, offering a
stiffer response and thus reduces the dynamic following error.
Figure 5.50: DC Motor Current 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 performed with such a driver are very smooth at high
and low speeds and has a similar dynamic following error.
In control signal
±
10V
But, when the highest possible performance is required, the best
choice is always the velocity feedback driver. This type of driver
requires a tachometer, an expensive and sometimes difficult to add
device (
Figure 5.51 ).
M
E
M
T
E
Figure 5.51: DC Motor Velocity Feedback Driver
V = velocity
control signal
±
10V
Section 5 – Motion Control Tutorial 5-37