GE Industrial Solutions AF-650 GP General Purpose Drive Programming Guide - Manual (Page 135)

3.21 PI-## PID Controls
Parameter group related to PID Controls
3.21.1 PI-0# Speed PID Control
Parameters to configure the Speed PID Control.
PI-00 Speed PID Feedback Source
Option: Function:
NOTE
This parameter cannot be
adjusted while the motor is
running.
Select the encoder for closed loop
feedback.
The feedback may come from a
different encoder (typically
mounted on the application itself)
than the motor mounted encoder
feedback selected in H-42 Flux
Motor Feedback Source.
[0] * Motor feedback par.
H-42
[1] 24V encoder
[2] OPCENC
[3] OPCRES
[6] Analog Input 53
[7] Analog Input 54
[8] Frequency input 29
[9] Frequency input 33
PI-02 Speed PID Proportional Gain
Range: Function:
0 * [0 - 1] Enter the speed controller proportional gain. Quick
control is obtained at high amplification. However if
amplification is too great, the process may become
unstable.
PI-03 Speed PID Integral Time
Range: Function:
8.0
ms *
[1.0 -
20000
ms]
Enter the speed controller integral time, which
determines the time the internal PID control
takes to correct errors. The greater the error,
the more quickly the gain increases. The
integral time causes a delay of the signal and
therefore a dampening effect, and can be used
to eliminate steady state speed error. Obtain
quick control through a short integral time,
though if the integral time is too short, the
process becomes unstable. An excessively long
integral time disables the integral action,
leading to major deviations from the required
reference, since the process regulator takes too
PI-03 Speed PID Integral Time
Range: Function:
long to regulate errors. This parameter is used
with [0] Speed open loop and [1] Speed closed
loop control, set in H-40 Configuration Mode.
PI-04 Speed PID Differentiation Time
Range: Function:
30.0
ms *
[0 -
200 ms]
Enter the speed controller differentiation time.
The differentiator does not react to constant
error. It provides gain proportional to the rate
of change of the speed feedback. The quicker
the error changes, the stronger the gain from
the differentiator. The gain is proportional with
the speed at which errors change. Setting this
parameter to zero disables the differentiator.
This parameter is used with H-40 Configuration
Mode [1] Speed closed loop control.
PI-05 Speed PID Diff. Gain Limit
Range: Function:
5 * [1 - 20] Set a limit for the gain provided by the differen-
tiator. Since the differential gain increases at higher
frequencies, limiting the gain may be useful. For
example, set up a pure D-link at low frequencies
and a constant D-link at higher frequencies. This
parameter is used with H-40 Configuration Mode [1]
Speed closed loop control.
PI-06 Speed PID Lowpass Filter Time
Range: Function:
10.0
ms *
[0.1 -
100
ms]
Set a time constant for the speed control low-
pass filter. The low-pass filter improves steady-
state performance and dampens oscillations on
the feedback signal. This is an advantage if there
is a great amount on noise in the system, see
Illustration 3.46. For example, if a time constant
(τ) of 100 ms is programmed, the cut-off
frequency for the low-pass filter will be 1/0.1= 10
RAD/s., corresponding to (10/2 x π) = 1.6 Hz. The
PID regulator only regulates a feedback signal
that varies by a frequency of less than 1.6 Hz. If
the feedback signal varies by a higher frequency
than 1.6 Hz, the PID regulator does not react.
Practical settings of PI-06 Speed PID Lowpass Filter
Time taken from the number of pulses per
revolutions from encoder:
Encoder PPR PI-06 Speed PID
Lowpass Filter Time
512 10 ms
1024 5 ms
2048 2 ms
4096 1 ms
Parameter Descriptions AF-650 GP Programming Guide
134 DET-618C
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