01/2007
14.4 Frequency response measurements
14-435
© Siemens AG 2007 All Rights Reserved
SINUMERIK 840Di sl Manual (HBIsl) – 01/2007 Edition
Alternatively, the interference frequency response can be recorded in order to
assess how well the control suppresses interference.
Measuring parameters
S Amplitude
This parameter determines the magnitude of the test signal amplitude. This
should give rise to only a very low speed of a few (approximately 1 to 2)
rev/min at the motor end.
S Bandwidth
The bandwidth parameter is used to set the analyzed frequency range. The
larger this value, the finer the frequency resolution and the longer the mea-
surement time. The maximum value is given by the position control cycle
(T
position
controller
): Bandwidth
max
[Hz] = 1 / (2 * T
position
controller
[sec])
Example:
Position control cycle: 2 ms
Bandwidth
max
= 1 / ( 2 * 2*10
–3
) = 250 Hz
S Averaging
The accuracy of the measurement and measurement duration increase with
this value. A value of 20 is normally suitable.
S 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 and 1 s
is recommended. Do not set too low a value for the settling times or the fre-
quency response and phase diagrams will be distorted.
S Offset
The measurement requires a slight speed offset of a few motor revolutions
per minute. The offset must be set to a higher value than the amplitude.
– The offset is run up via an acceleration ramp.
– The acceleration value is defined for one
Axis: MD 32300: MAX_AX_ACCEL
Spindle: MD 35200: GEAR_STEP_SPEEDCTRL_ACCEL
MD 35210: GEAR_STEP_POSCTRL_ACCEL
– The following applies: Acceleration value = 0, no ramp
Acceleration value > 0, ramp active
– The actual measuring function becomes active only when the offset
value is reached.
The transient response (response to setpoint changes or disturbances) of the
speed control in the time range can be assessed with the step stimulation func-
tion. The test signal is connected to the speed controller output for recording of
the response to disturbances.
Measuring parameters
S Amplitude
Magnitude of the setpoint or disturbance step change.
S Measurement time
The period of time recorded (maximum: 2048 speed controller cycles).
Measurement
setpoint/
disturbance step
changes
14 Drive O
timization with HMI Advanced
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