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Chapter 1
Background
Table 1 - Bandwidth Comparison for Various Drive and Motor Combinations
Drive or
Servo Control
Module
Loop Update Rate
Position
Velocity
Torque
Motor
Bulletin No.
Drive Model
Torque Loop
Time Constant Bandwidth
Kinetix 6000
Kinetix 6200
Kinetix 6500
125 μs
125 μs
125 μs
MPL-S/M (1)
510.9 μs
311.5 Hz
MPL-E/V (1)
538.25 μs
295.6 Hz
MPL-H (2)
1531 μs
103.95 Hz
MPL-S/M (1)
1003.9 μs
158.53 Hz
Kinetix 350
500 μs
500 μs
125 μs
MPL-E/V
(1)
1031.25 μs
154.33 Hz
MPL-H (2)
2024 μs
78.65 Hz
TLY
1062.5 μs
149.8 Hz
Kinetix 5500
125 μs
125 μs
125 μs
VPL
537 μs
296.34 Hz
1756-M02AE
Servo Module
500 μs
250 μs
—
—
1502 μs
106 Hz
(1) This motor has a high-resolution encoder.
(2) This motor has an incremental (low resolution) encoder.
Damping Factor
Damping factor is commonly referred to as zeta (z). It affects the rise time for a
given bandwidth. The following figure shows how the damping factor affects
actual response with feed forwards disabled (solid) compared to its command
motion profile (dashed).
Figure 9 - How Damping Affects Transient Response
• A damping factor of z = 0.8 produces high responsiveness, which is
characterized by a faster rise time, but with overshoot.
• A damping factor of z = 1.0 produces medium responsiveness, which is
characterized by the fastest possible rise time without overshoot. We
recommend this setting.
• A damping factor of z = 1.5 produces low responsiveness, which is
characterized by a slower response, similar to decreasing the bandwidth.
The default setting in a Sercos drive is z = 0.8 and the default setting in an
EtherNet/IP drive is z = 1.0. A lower damping factor decreases the spacing
between the position, velocity, and torque loop bandwidths, generating underdamped responses in actual position and actual velocity trends. A higher
damping factor generates over-damped responses.
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Rockwell Automation Publication MOTION-AT005B-EN-P - November 2015