KSB PumpDrive 2 - Parameters of the PID Controller; Automatic Determination of Controller Parameters

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PumpDrive 2
The PID process controller is set using the following parameters:
Parameter (3-6-4-2) defines the proportional constant of the controller. The control
deviation is transferred to the control value, amplified by the proportional gain.
To avoid a permanent control deviation, an integrating controller constant is
required for many hydraulic processes. For this purpose, parameter (3-6-4-3) is used
to define the integral time of the integral constant. The control deviation is
integrated over time, weighted in relation to the integral time selected and added to
the control value. Reducing the integral time leads to faster adjustment or
compensation for the control deviation. When an integral time of 0s is selected, the
integral constant is deactivated.
By leveraging the differential constant, the controller can respond to a quick change
in the control deviation. Whether a differential constant is necessary is a function of
the dynamics of the hydraulic process; for typical centrifugal pump applications, it is
not required. When a rate time of 0s is selected, the differential constant of the
process controller is deactivated. The rate time of the differential constant is defined
using parameter (3-6-4-4). By increasing the rate time, the response to quick changes
in the control deviation is intensified. The Differential Constant Limitation parameter
(3-6-4-8) is used to define the maximum differential gain, which will help limit the
effect of measurement noise on the control value. Decreasing the limitation value
restricts the influence of the differential constant at high frequencies, and the
influence of measurement noise can be suppressed.
Table51: Parameters of the PID controller
Parameter Description Possible settings Factory setting
3-6-4-2 Proportional Constant
Setting the proportional constant of the
controller
0,01...100,00 1,00
3-6-4-3 Integral Time (Integral Constant)
Setting the integral constant of the
controller
0,0 to 9999,9 s 0,2 s
3-6-4-4 Rate Time (Differential Constant)
Setting the differential constant of the
controller
0,00... 100,00s 0,00s
3-6-4-8 Differential Constant Limitation
The maximum differential gain is limited in
order to suppress measurement noise, for
example.
1,00...20,00 3,00
Automatic determination of controller parameters
The parameters of the process controller can be determined automatically while the
hydraulic process is underway. To this end, a test sequence involving speed changes is
carried out and evaluated automatically. The test sequence is started as follows:
1. Operate the single-pump system or multiple pump system with the type of
control required using a PI controller and the relevant setpoint.
2. Run up the hydraulic system to reach the typical operating conditions in terms
of pressure and flow rate.
3. Once an adjusted and largely stable operating point is reached, start the test
sequence for automatically determining the controller parameters via
parameter 3-6-4-1-1.
ð The display now shows the Automatic Determination of Controller
Parameters Active message.
After the test sequence has been completed, the values determined for the
proportional constant, integral time and, if required, the rate time of the controller
are written to the respective parameters. In addition, the Operating Point parameter
(3-6-4-5) is als set to the current speed. The display now shows the Automatic
Determination of Controller Parameters Finished message.
The single-pump system or multiple pump system continues to operate uninterrupted
with the new controller parameters. If the process of determining the controller
parameters could not be completed correctly, the display shows the Automatic