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Type: |
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Address: |
RMC75: Gain Set #0: %MDn.63 Gain Set #1: %MDn.130 where n = 12 + the axis number RMC150: Gain Set #0: %MDn.63 Gain Set #1: %MDn.130 where n = 24 + the axis number RMC200: Gain Set #0: %MDn.202 Gain Set #1: %MDn.232 where n = 384 + the axis number |
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System Tag: |
Gain Set #0: _Axis[n].DiffGain Gain Set #1: _Axis[n].DiffGain_2 where n is the axis number |
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How to Find: |
Axes Parameters Pane, All tab: Position/Velocity Control |
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Data Type: |
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Units: |
Position Control: %/(pu/sec) Velocity control: %/(pu/sec2) % = percent of maximum Control Output (default is 10V) |
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Range: |
≥ 0 |
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Default Value: |
0 |
Description
The Differential Gain may greatly enhance performance on many motion systems. On velocity drives or hydraulic systems, Differential Gain will tend to dampen out oscillations 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
Dn = (VTargetn - VActualn) x KD
Velocity PID
Dn = (ATargetn - AActualn) x KD
Position I-PD
Dn = - (VActualn - VActualn-1 ) x KD
Velocity I-PD
Dn = - (AActualn - AActualn-1 ) x KD
where
Dn = Differential Term at sample n [% of maximum Control Output]
V = Velocity [pu/sec]
A = Acceleration [pu/sec2]
KD = Differential Gain [%/(pu/sec) or %/(pu/sec2)]
pu = position-unit
See Also
Parameter Registers | Differential Output Term
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