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Overview
1.1. Understanding Basic QNP3 Stage Operation
QNP3 stages have many operating characteristics that are unique to piezo actuator based systems. This
section describes some of the unique aspects of QNP3 stages. It is strongly recommended that all QNP3
stage users read the
"Appendix C: Piezo Engineering
information on operation principles and nomenclature.
Expansion Device
The piezo actuator in each QNP3 stage is an expansion device that expands proportionately with applied
voltage. This has some practical implications for stage use. When de-energized (0 V), the actuator will
compress and the stage will sit at one end of travel. When energized with positive voltage the actuator will
expand and the stage will move toward the opposite end of travel. When energized with negative voltage the
actuator will shrink and the stage will move further away from the center relative to the de-energized position.
Each QNP3 stage is marked with arrows that indicate the direction of expansion (i.e. the positive voltage
direction).
Figure 1-1:
Open-Loop vs Closed-Loop Travel
All QNP3 stages with feedback (-C option) have an open-loop (OL) and closed-loop (CL) travel range (refer to
Section
1.4.). This refers to whether the stage is using feedback control (CL) or not (OL). QNP3 stages
purchased without feedback have an open-loop travel range only. The open-loop range is the travel that can
be achieved over the entire -30 to 150 V operation range. When the stage is in closed-loop (servo on), it
requires over-travel to account for a variety of operational conditions, so the closed-loop range is smaller.
Refer to
Figure 1-1
for an illustration of QNP3 stage travel ranges. QNP3 stages with the -C option are
calibrated at the factory for optimal linearity over the specified closed-loop range only.
Unless otherwise specified, QNP3 stages configured at Aerotech default to open-loop operation and must be
commanded to enter closed-loop mode. By default, all open-loop motion commands control voltage and all
closed-loop motion commands control position. Refer to controller documentation for information on how to
turn the servo on and off and adjust default settings.
10
Tutorial" (or at www.aerotech.com) for more detailed
Single-Axis Stage Travel and Voltage Relationship
Chapter 1
QNP3 Hardware Manual
www.aerotech.com
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