Double Differential Gain

Type:	Axis Parameter Register
Address:	RMC75: Gain Set #0: %MDn.69 Gain Set #1: %MDn.136 where n = 12 + the axis number RMC150: Gain Set #0: %MDn.69 Gain Set #1: %MDn.136 where n = 24 + the axis number RMC200: Gain Set #0: %MDn.203 Gain Set #1: %MDn.233 where n = 384 + the axis number
System Tag:	Gain Set #0: _Axis[n].DblDiffGain Gain Set #1: _Axis[n].DblDiffGain_2 where n is the axis number
How to Find:	Axes Parameters Pane, All tab: Position/Velocity Control → Gain Set#
Data Type:	REAL
Units:	Position Control: %/(pu/sec2) Velocity control: %/(pu/sec3) % = percent of maximum Control Output (default is 10V)
Range:	≥ 0
Default Value:	0

Description

The Double Differential Gain is available only on position and velocity axes with the High-Order Control parameter set to Accel Control. The Double Differential Gain controls how much of the Control Output is is added to the PFID Output due to the difference between the Target Acceleration and the Actual Acceleration or Target and Actual Jerk for position or velocity control, respectively. Position control is defined as when the Current Control Mode is Position PID. Velocity control is defined as when the Current Control Mode is Velocity PID.

Each gain of the axis contributes to the Control Output. The contribution from the Double Differential Gain is called the Double Differential Output Term.

Advanced: I-PD Control

The Double Differential Gain controls how much the PFID Output is adjusted based on the change in the Actual Acceleration or Actual Jerk for position or velocity control, respectively. Position control is defined as when the Current Control Mode is Position I-PD. Velocity control is defined as when the Current Control Mode is Velocity I-PD.

Tuning

See the Tuning Active Damping and Acceleration Control topic for details.

Definition

PositionPID

Dn = (ATargetn - AActualn) x KDD

Velocity PID

Dn = (JTargetn - JActualn) x KDD

Position I-PD

Dn = - (AActualn - AActualn-1 ) x KDD

Velocity I-PD

Dn = - (JActualn - JActualn-1 ) x KDD

where

Dn = Double Differential Term at sample n [% of maximum Control Output]

A = Acceleration [pu/sec2]

J = Acceleration [pu/sec3]

KDD = Double Differential Gain [%/(pu/sec2) or %/(pu/sec3)]

pu = position-unit

The Double Differential Gain units are: Percent of the maximum Control Output per position units per second squared (pu/sec2). The default value of the maximum Control Output is 10V, but can be changed using the Output Scale parameter.