ADLINK PCI-8258 - Manual (Page 109)

Motion Control Theory 95
PCI-8254 / PCI-8258
a Set up initial and closing frequency and data points
of Bode plot:
The frequency range of a Bode plot is determined by its
initial and closing frequency. As too small a initial value
may boost calculation time, please try to start at around
10Hz. The closing frequency should not be greater than
500Hz as it is limited by driver and internal sampling
rate. Each Bode plot contains frequency, gain, and
phase data. Number of data points determines the
resolution of frequency response. Please note that the
better the resolution is the more calculation time is
required.
b Set up size of sine wave amplitude:
The amplitude should be set according to the relation
between motor resolution versus actual distance unit of
measure as oversized amplitude may lead to incorrect
outcome as the calculation error may be too big while
undersized one may affect machine safety adversely.
Take example. A motor resolution at 10000 pulse/rev
may need to set the amplitude to around 300 pulse.
c Set up update cycle of each data points of the Bode
plot:
Length of update cycle time may affect number of
sampling points required for calculating Bode plot's data
point. Take example. In case of update cycle at 0.1
second, sampling speed at 10KHz, and frequency range
at 10Hz~100Hz the required sampling points for each
Bode plot's data point is 1000. This may affect the
accuracy in calculating frequency response. In most
cases the longer the better.
d Determine frequency response type:
The system now supports three types of frequency
response: closed circuit system, open circuit system and
plant. See earlier descriptions for detail.