Functions
09.2008
6SE7087-6QX70 (Version AK)
Siemens AG
7-62
Compendium Motion Control
SIMOVERT MASTERDRIVES
An examination of the transmission function of the open speed control
loop (e.g. using the built-in noise excitation, function diagram 796)
provides information about the amplitude and phase margin of the
control loop for critical frequencies. As the filters always change the
phase progression it also possible to change the phase margin
specifically by applying filters. For example, the phase of frequencies
above the blocking frequency is raised by a band-stop filter, which can
be utilized to increase the phase margin.
As low natural frequencies always have a detrimental effect on the
dynamics and therefore fault suppression of the system, it is worth
examining the source of natural frequencies in the mechanical system.
By measuring the transmission functions with additional encoders, the
measured natural frequencies can be assigned to the mechanical
components and their frequencies increased specifically by using more
rigid components or lighter masses.
Low pass (P256 = 2; P254 = 50 Hz)
1
10
100
1
.
10
3
-6
-4.5
-3
-1.5
0
1.5
3
Frequency in Hz (no omega!)
3
-6
Ampl
fmax
fmin
Frequency
-180
-135
-90
-45
0
45
90
135
180
180
Phase
1
10
100
1
.
10
3
Frequency in Hz (no omega!)
fmax
fmin
Frequency
-180
Example 1
