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03.96
10.5 Frequency response measurement
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 Siemens AG 2000 All Rights Reserved
SINUMERIK 840D Installation and Start-Up Guide (IAD) – 04.00 Edition
The effects of these measures can also be checked in the time range.
Amplitude
This parameter determines the magnitude of the test signal amplitude. It should
be set to the smallest possible value (e.g. 0.01 mm).
Offset
The measurement requires a slight speed offset of a few motor revolutions per
minute. The offset must be set such that no speed zero crossings occur at the
set amplitude.
Bandwidth
Setting of analyzed frequency range (maximum setting = half the position con-
troller sampling frequency). The lower this value, the finer the frequency resolu-
tion and the longer the measurement time. The maximum value corresponds to
half the position controller sampling rate (e.g. 200 kHz with position controller
sampling time of 2.5 ms).
Averaging operations
The accuracy of the measurement, but also the measurement time, are in-
creased with this value. A value of 20 is normally suitable.
Settling time
This value represents the delay between recording of the measured data and
injection of the test setpoint and offset. A value of between 0.2 s and 1 s is rec-
ommended. Do not set too low a value for the settling times or the frequency
response and phase diagrams will be distorted.
The transient or positioning response of the position control in the time range,
and in particular the effect of setpoint filters, can be assessed with the step and
ramp stimulation functions. If an offset value other than zero is input, the step
change is stimulated during traversal. For the sake of clarity, the displayed posi-
tion actual value does not include this speed offset. The following quantities can
be measured:
S Actual position value (active position measuring system)
S Control deviation (following error)
Amplitude
This parameter determines the magnitude of the specified setpoint step change
or ramp.
Offset
The step is stimulated from standstill or starting from the constant traverse
speed set in this parameter.
Measurement time
This parameter determines the period of time to be recorded (maximum: 2048
position controller cycles).
Settling time
This value represents the delay between measured data recording and test
setpoint output and the injection of the offset.
Ramp duration
In basic setting Setpoint ramp the position setpoint is preset according to the
set ramp duration. In this case, the acceleration limits which currently apply to
the axis or spindle are effective.
Measurement
parameters for
reference
frequency
response
Setpoint step
change and
setpoint ramp
Measurement
parameters for
setpoint step
change and
setpoint ramp
10 Drive Optimization with Start-Up Tool
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