122 Rockwell Automation Publication 750-RM100A-EN-P - August 2019
Chapter 11 Application References
• The experimental method involves displacing of the load to an initial
angle, letting it oscillate for a time period of T seconds while counting the
number of swings n. With this knowledge, frequency is derived as:
Knowing the accurate cable length is important as it affects the center frequency
of the notch filter. The following experimental result shows how deviation from
the actual cable length affects the sway magnitude when the filter frequency does
not accurately match the sway oscillation frequency. The sway magnitude
increases as the cable length error becomes higher as shown in Figure 45
.
Figure 45 - Sway Magnitude (Degrees) vs. Cable Length Error (Percent)
Cable Length Variation
Based on the application, the cable length can vary between a minimum and
maximum length (Lmin and Lmax), which results in a varying sway frequency.
See Figure 46
. The range of such length change can determine the system
configuration.
A larger variation of cable length can result in a larger variation in frequency.
Figure 46 - Simple Diagram for Anti-Sway Application
8
7
6
5
4
3
2
1
0
-60% -40% -20% 0% 20% 40% 60%
Cable Length Implied by Notch Filter / True Cable Length
Sway Magnitude (Degrees)
Trolley
Z- axis Hoist
L
min
Load
L
max
Sway magnitude
(degrees)
Y- axis
Gantry
Load
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