Acceleration Feed Forward

Type:	Axis Parameter Register
RMC70 Address:	Gain Set #1: Fn:66 Gain Set #2: Fn:133 where n = 12 + the axis number
RMC150 Address:	Gain Set #1: Fn:66 Gain Set #2: Fn:133 where n = 24 + the axis number
System Tag:	Gain Set #1:_Axis[n].AccFFwd Gain Set #2:_Axis[n].AccFFwd_2 where n is the axis number
How to Find:	Axes Parameters Pane, Tune tab: Position/Velocity Gains
Data Type:	REAL
Units:	%/(pu/s2)
Range:	≥ 0
Default Value:	0

Description

The Acceleration Feed Forward causes the controller to give Control Output proportional to the Target Acceleration. Acceleration Feed Forward is only applied when the axis is in Closed Loop control and accelerating or decelerating. It helps the axis maintain the Target Position.

The Acceleration Feed Forward Term is the portion of the Control Output resulting from the Acceleration Feed Forward Gain.

This parameter is not used in the Position I-PD or Velocity I-PD control modes.

Definition

The Acceleration Feed Forward Term is calculated from the Acceleration Feed Forward as follows:

DAFFn

KAFFATargetn

where

DAFFn	=	Acceleration Feed Forward Term at sample n [% of maximum Control Output]
KAFF	=	Acceleration Feed Forward [%/(pu/sec2)]
ATargetn	=	Target Acceleration at sample n [pu/sec2]

Tuning

The Acceleration Feed Forward helps the axis track the Target Position while the axis is accelerating and decelerating. This makes it "easier" for the other gains to control the position of the axis.

The Acceleration Feed Forward should not be adjusted until the Velocity Feed Forward is adjusted correctly. See the Tuning topic for more details on how to properly adjust the Acceleration Feed Forward.