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Chapter 3
Hardware Overview
Closed-loop stepper axes also require a feedback resource, while open-loop stepper axes do not.
Figures 3-4 and 3-5 show these axis configurations.
With the NI 7340 motion controller, you can map one or two feedback resources and one or two
output resources to the axis. An axis with its primary output resource mapped to a stepper output
is by definition a stepper axis. An axis with its primary output resource mapped to a DAC is by
definition a servo axis.
Figure 3-4.
Servo Axis Resources
Figure 3-5.
Stepper Axis Resources
The NI 7340 motion controller supports axes with secondary output resources, such as DACs for
servo axes or stepper outputs. Defining two output resources is useful when controlling axes
with multiple motors, such as gantry systems in which two DAC outputs can be configured with
different torque limits and/or offsets.
The NI 7340 motion controller also supports secondary feedback resources, called encoders, for
axes defined as servo. Two feedback resources are used when implementing dual-loop control,
such as in backlash compensation, which reduces the number of encoders available for other
axes.
Note
Refer to the
NI-Motion Help
for information about configuring axes.
Motion Resources
Encoder, DAC, ADC, and motion I/O resources that are not used by an axis are available for
non-axis or nonmotion-specific applications. You can directly control an unmapped DAC as a
general-purpose analog output (±10 V). Similarly, you can use any ADC channel to measure
potentiometers or other analog sensors.
01011101101
11101101100
PID
S
ervo
Loop
16-Bit
D/A
Converter
3
2-Bit
Encoder
Interf
a
ce
±10 V
øA
øB
Index
01011010
010010110
S
tepper
Control
Loop
S
tepper
P
u
l
s
e
Gener
a
tor
3
2-Bit
Encoder
Interf
a
ce
øA
Index
Tr
a
jectory
Gener
a
tor
Option
a
l
Summary of Contents for PXI-7340
Page 1: ...PXI 7342...
