Delta RMC151 - Manual (Page 981)

9 Register Reference
If either Feed Forward is set to zero, or they are identical, the gain ratio will be one.
Otherwise, for the direction of the largest Feed Forward, the gains will be applied as they.
In the direction of the smallest Feed Forward, the gains will be multiplied by the ratio of
the smallest Feed Forward divided by the largest feed forward.
Definition
The Velocity Feed Forward units are: percent of the maximum Control Output per
position-units per second (pu/sec). The maximum Control Output is 10V, but can be
changed using the Output Scale parameter.
The Velocity Feed Forward Term is calculated from the Velocity Feed Forward as follows:
D
VFF
n = K
VFF
V
Target
n
where
D
VFF
n = Velocity Feed Forward Term at sample n [% of maximum Control
Output]
K
VFF
= Velocity Feed Forward [%/(pu/s)]
V
Target
n = Target Velocity at sample n [pu/s]
Tuning
The Velocity Feed Forwards help the axis maintain the Target Position while the axis is
moving. This makes it "easier" for the other gains to control the position of the axis. See
the Tuning topic for details on how to properly adjust the Velocity Feed Forward.
9.2.2.4.11. Velocity Feed Forward (Negative)
Type: Axis Parameter Register
RMC70 Address: Gain Set #1: %MDn.68, where n = 12 + the axis number
Gain Set #2: %MDn.135, where n = 12 + the axis number
RMC150 Address: Gain Set #1: %MDn.68, where n = 24 + the axis number
Gain Set #2: %MDn.135, where n = 24 + the axis number
System Tag: Gain Set #1: _Axis[n].VelFFwdN
Gain Set #2: _Axis[n].VelFFwdN_2
where n is the axis number
How to Find: Axes Parameters Pane, Tune tab: Position/Velocity Gains
Data Type: REAL
Units: %/(pu/s)
Range: ≥ 0
Default Value: 0
Description
The Negative Velocity Feed Forward is one of the gains. It causes the controller to give an
amount of Control Output proportional to the speed of the velocity of the axis.
The Negative Velocity Feed Forward applies when the Control Output is negative. The
Positive Velocity Feed Forward applies when the Control Output is positive. The Velocity
Feed Forwards are only applied when the axis is in Closed Loop control. They help the
axis maintain the Target Position while the axis is moving at constant velocity.
The Positive and Negative Velocity Feed Forwards are available only on position or
velocity axes with ratioed gains. Position or velocity axes with symmetrical gains have
only one Velocity Feed Forward.
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