Delta RMC151 - Manual (Page 978)

RMC70/150 and RMCTools User Manual
and help the axis track during acceleration and deceleration. On torque drives, the
differential gain is essential for providing damping to the motor.
The Differential Gain controls how much of the Control Output is added to the PFID
Output due to the difference between the target and actual velocity or target and actual
acceleration 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.
A disadvantage of Differential Gain is that it amplifies position measurement noise. If
there is too much noise or the gain is too high, this can cause the system to chatter or
oscillate.
Each gain of the axis contributes to the Control Output. The contribution from the
Differential Gain is called the Differential Output Term.
See Tuning topic for details on how to properly adjust the Differential Gain.
Advanced: I-PD Control
The Differential Gain controls how much the PFID Output is adjusted based on the change
in the Actual Velocity or Actual Acceleration 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.
Definition
The Differential Gain units are: percent of the maximum Control Output per control units
(position-units or velocity-units) per second (cu/sec). The maximum Control Output is
10V, but can be changed using the Output Scale parameter.
The Differential Output Term control is calculated from the Integral Gain as follows:
Position PID
D
n
= (V
Target
n - V
Actual
n) x K
D
Velocity PID
D
n
= (A
Target
n - A
Actual
n) x K
D
Position I-PD
D
n
= - (V
Actual
n - V
Actual
n-1 ) x K
D
Velocity I-PD
D
n
= - (A
Actual
n - A
Actual
n-1 ) x K
D
where
D
n
= Differential Term at sample n [% of maximum Control Output]
V = Velocity [pu/sec]
A = Acceleration [pu/sec
2 ]
K
D
= Differential Gain [%/(pu/sec) or %/(pu/sec 2 )]
pu = position-unit
9.2.2.4.9. Velocity Feed Forward
Type: Axis Parameter Register
RMC70 Address: Gain Set #1: %MDn.65, where n = 12 + the axis number
Gain Set #2: %MDn.132, where n = 12 + the axis number
RMC150 Address: Gain Set #1: %MDn.65, where n = 24 + the axis number
958 Delta Computer Systems, Inc.