Fourier Analysis; Measurement Range (Bandwidth), Measurement Time - Siemens SINUMERIK 840C Installation Instructions Manual

08.96
12.33.1.1

Fourier analysis

The integrated Fourier analysis function provides you with a particularly effective tool for
optimizing the speed controller. It allows you to assess the speed control settings and the
mechanical properties of the machine.
To reach the Fourier analysis (frequency response method), please select Startup Drive
servo startup Startup function .
The frequency response method supplies exact and reproducible results even with very low
test signal amplitudes. You can adapt the measurement parameters to the individual
application.
The results of the Fourier analysis are displayed in a Bode diagram. A Bode diagram consists
of two graphs, i.e. the amplitude response curve and the phase response curve.
The phase is at 0 in the lower frequency range. It rotates to negative phase angles as the
frequency increases. If the phase angle exceeds I180°I, the graph representation is reversed,
i.e. it jumps from –180° to180° or from 180° to–180°.
12.33.1.2

Measurement range (bandwidth), measurement time

The bandwidth is calculated as follows on the SINUMERIK 840C/611D:
Max. bandwidth =
2 x speed controller clock cycle
The bandwidths are as follows depending on the speed controller clock cycle:
• Clock cycle= 62.5µs
• Clock cycle= 125µs
• Clock cycle= 250µs
• Clock cycle= 500µs
Owing to the short measurement times, traversing distances of a few mm are sufficient for the
required response measurement. The measurement time is calculated as follows:
Measurement time[s] =
The measurement time is 6.5 seconds with 20 averaging operations. With an offset of 5
rev/min, a traversing range of less than 0.55 revolutions is required for the measurement.
© Siemens AG 1992 All Rights Reserved
SINUMERIK 840C (IA)
1
Bandwidth = 8 kHz.
Bandwidth = 4 kHz.
Bandwidth = 2 kHz.
Bandwidth = 1 kHz.
512 x No. of averaging operations
Bandwidth [Hz]
6FC5197- AA50
12 Functional Descriptions
12.33.1 Introduction
+ settling time
12–335