Current Amplifier; Voltage Amplifier; Stepper Motor Power Amplifiers; Stepper Motor System Without Position Feedback - Addi-Data APCI-8001 Commissioning Manual

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6.2.2 Current amplifier

When using a power module that has been designed as a current amplifier, a PD controller (kp, kd, kpl) is
required. To prevent the contouring error during traversing and in the event of static loading of the motor
shaft, an additional integral component can also be used here. As a rule of thumb, you can assume the
following equation:
T N >= 5 * T V
and
T V >= 5 * T A
Now you can use kp to vary the settings until you find the best working point. At this working point, you can
use kpl to vary the settings again. If the system becomes stable, but is too soft, the T V / T A ratio can be
reduced.

6.2.3 Voltage amplifier

When using a power module that has been designed as a voltage amplifier, a P or PD controller is required.
The position error under static loading can be prevented by an additional integral component. Experimental
filter parameter settings are made in the same manner as for the speed controller. The controller hardness
can be improved by the derivative component with which the motor's mechanical or the electrical time
constant can be compensated.

6.2.4 Stepper motor power amplifiers

6.2.4.1 Stepper motor system without position feedback

When using stepper motor power amplifiers without displacement feedback, all that is needed is a
proportional controller with an amplification of kp = 0.04 and a forward compensation. All other filter
parameters are automatically set to 0. The controller parameters are automatically set by the system. It is not
possible for the user to make any settings.
Although this seems to be an open-loop system, the control loop must still be closed with CloseLoop when
the axis is handled. Here, the actual value is the number of steps that are actually output. In this mode,
verification with actual value encoders is possible. However, the encoder value is kept in the aux variable
(rdaux, wraux functions) und in the digits unit without conversion.

6.2.4.2 Power amplifier with step/direction setpoint value input and position control

For the control unit, the same specifications as with stepper motors without position feedback apply when
power amplifiers with a step/direction setpoint value specification are used, which are operated in the Closed-
Loop mode, i.e. with displacement feedback. Here, however, a permanent step error will not occur as the
position is controlled by the power amplifier. In such a configuration, different motor types like direct current
motors, asynchronous motors, electronically commutated motors or stepper motors can be used.

6.2.5 Pre-control

Using parameters kfca and kfcv, an acceleration and velocity pre-control signal can be created. The pre-
control feature enables the contouring error to be reduced during positioning operations. The stability of the
control loop is not affected by the pre-control function.
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