NI 9503 C Series Stepper Drive Modules and SoftMotion Module
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© National Instruments
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9
Table 2.
Stepper Drive (Getting Started) Loop Descriptions
Table 3.
FPGA Loop Name
Description
Fault Monitoring Loop
The Fault Monitoring loop sends fault information, including
user-defined faults, to the NI SoftMotion engine and sends the
state machine implemented in the Control Status Loop into a
fault state.
Control Status Loop
The Control Status Loop interprets the Control Register UDV
and recognizes state changes, executes the appropriate action on
a state change, and generates the Status Register UDV that
returns information to the SoftMotion Engine.
Reset Monitoring Loop
The Reset Monitoring Loop latches the reset variable so that it
only changes on a rising edge of the Scan Clock. This allows
proper operation of the SoftMotion Motor Control VIs with a
reset
input.
Mailbox Loop
The Mailbox Loop transfers axis configuration and other data
between the SoftMotion Engine and the LabVIEW FPGA
Module. The transferred data is written to FPGA memory and
accessed using the Read Motion Memory and Write Motion
Memory Drive Interface VIs. This loop is required to be
implemented as-is for proper operation
Synchronization Loop
The Synchronization Loop synchronizes the FPGA clock
(slave) to the RT clock (master) to correct for drift and jitter.
This is the preferred synchronization method to use with the
NI SoftMotion Module. The Synchronization Loop is required
to be implemented as-is for proper operation.
Position Loop and
Current Loop
The Position Loop receives position setpoints from the
SoftMotion trajectory generator and uses the Spline
Interpolation VI to generate intermediate setpoints, resulting in
smoother motion. It converts the position setpoints to an
electrical angle, which is used to generate phase A and phase B
current setpoints. The Position Loop sends current setpoints to
the Current Loop
PWM Loop
The PWM Loop takes the A+, A-, B+ and B- duty cycles and
converts them into digital signals that control H-bridges on the
drive. The PWM Loop also triggers the Current Loop to run at
the midpoint of the high phase of the PWM duty cycle.
