Ndrive HP 10/20/30 User’s Manual
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4-19
4.2.1. PSO Tracking Rate Configuration
PSO Track Rate Configuration applies to an Ndrive with
either the -DUALPSO or -TRIPLEPSO options, and the
MXH option, with high encoder data rates.
A)
The maximum clock frequency of the MXH multiplier should be limited to 20 MHz.
when using the -DUALPSO or -TRIPLEPSO options. This is due to a maximum encoder
date rate of approximately 32 MHz. on the Ndrive’s encoder input ports. The 20 MHz.
clock rate is achieved by setting the “Clock Select 1” field of the CfgFbkEncMxhSetup
axis parameter (value of 0x1 as shown below). This must be done when using -
DUALPSO or -TRIPLEPSO options in order to ensure that encoder count information is
not lost.
The 20 MHz. data rate limitation effectively limits the maximum speed of the axis (see
B
below). In addition, the -DUALPSO or -TRIPLEPSO options have a maximum tracking
rate of 5 MHz. due to hardware limitations. The PSO data rate can be reduced to 5 MHz.
while allowing the servo loop to operate at 20 MHz. by using the following
PSOTRACK
<axis>
SCALE 4 4 4
command. This command divides the encoder
signals before the PSO counters by a factor of 4 and therefore limits the frequency seen
by the PSO tracking counters to 5 MHz. However, the servo loop is still able to run at the
full 20 MHz. rate.
The effective PSO programming resolution is now 1/4 that of the servo loop (full)
resolution. PSODISTANCE commands should be entered 4 times lower than the full
resolution in this case.
Figure 4-18.
PSO Tracking Rate Block Diagram
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