Evaluation Of The Signal Quality - Lenze i950 Commissioning Manual

Configuring the feedback system
Second feedback system for the techology application
Encoder settings
12.2.3.4

Evaluation of the signal quality

Signal quality
The signal quality is evaluated by the parameter 0x2C52:004, which serves to monitor the ini-
tial reading and setting of the position.
If a transmission error occurs
the current angular drift is marked as invalid in the parameter , bit 9.
•
the inverter keeps its operating status.
•
Angular drift
Communication with the encoder is no longer monitored during the angular
drift determination.
The value displayed in 0x2C52:003
type:
Determination of the current angular drift for the sin/cos encoder
•
In the case of an incremental SinCos encoder, the pulses between two zero pulse events of
the Z-track are counted. Assuming that there are no faults, this value corresponds to the
set number of increments. The accuracy of this process corresponds to ± 1 increment grad-
uation of the encoder, with the difference between the set number of increments and the
counted pulses being converted to an angle with an accuracy of ±0.1°. The disadvantage is
that an updated angular drift value only becomes available at the end of a complete
encoder revolution. In turn, this means that the update rate depends on the speed.
Determination of the current angular drift for the SinCos-Hiperface® absolute value
•
encoder
In the case of a SinCos absolute value encoder with HIPERFACE® protocol, no Z-track is
available; instead, the position is regularly read out of the encoder. When the first encoder
read-out operation is performed (after power-up or elimination of wire breakage), the
encoder position is used to initialise the internal device counter unit and to set an internal
device position. All other read-out processes from the encoder are used to generate a dif-
ference between the internal device position and the encoder position. Assuming that
there are no faults, the difference is zero. However, the dead time of the communication
with the encoder means that the accuracy of the process is dependent on the speed and
therefore restricted compared to the zero pulse process. However, the advantage is that
the update rate does not depend on the speed, but is instead only determined by the com-
munication rate. The update rate is encoder-specific and is generally in the range between
30 ... 50 ms.
Parameter
Address Name / setting range / [default setting]
0x2C52:003 Load encoder/master encoder settings (encoder):
Angle drift
• Read only: x.x °
0x2C52:004 Load encoder/master encoder settings (encoder):
Actual amplitude signal quality
• Read only: x %
198
is determined in different ways depending on the encoder
Info
Display of the angular drift of the current angle error.
The signal quality indicates the actual amplitude of the SinCos analog
signals with regard to 1 Vss = 100 %.
• The signal quality should be between 95 ... 105 %.
• There is no need for optimisation if the signal quality is within the tol-
erance zone for the analog encoder signals given in the data sheet of
the encoder manufacturer.