Siemens SINUMERIK 840D sl Function Manual page 410

Compensations (K3)
5.7 Neural quadrant error compensation
● $AA_QEC_MEAS_TIME_1/_2/_3
Parameter acceptance
The QEC system variables are stored in the non-volatile user memory after the NC program
is started where they remain unchanged until the memory is erased or reformatted or until a
new learning or relearning process takes place or until they are written by the NC program.
Before the learning cycle is called, all system variables must be assigned valid values for the
learning process. This can be done, for example, in a subroutine. After this NC program has
run and a reset has been performed, the QEC data are active.
Characteristic data
The characteristic data determined during the learning process are stored as system
variables in the user memory reserved for this purpose.
Format: $AA_QEC[n] Range of n: 0 ... 1024
These values write the learned characteristic in internal formats and must therefore not be
changed!
Quantization of characteristic
The quantization, and thus the resolution, of the characteristic is defined via the two
quantities fine quantization($AA_QEC_FINE_STEPS) and coarse quantization
($AA_QEC_COARSE_STEPS). The finer the resolution, the higher the memory requirement
and the longer the duration of time required for the learning phase.
The number of memory locations required and the total number of quantization intervals is
calculated by the formula:
Number of memory locations = $AA_QEC_FINE_STEPS * ($AA_QEC_COARSE_STEPS+1)
Up to 1025 memory locations per axis can be reserved. In this way, a sufficiently high
resolution is achieved for high precision requirements.
The following 3 diagrams illustrate the meaning of the characteristic values for coarse and
fine quantization, and their effect on the teach-in period, as a function of the parameter
"Detailed learning active y/n". Three cases are distinguished for better understanding.
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"Measurement time for calculating the error criterion in acceleration range 1/2/3"
The measurement time is started, as soon as the criterion for injection of the
compensation value is fulfilled (i.e. the set speed changes sign). The end of the
measurement time is defined by the set parameter values.
Different measuring times are required for each characteristic range.
Recommended values for
– $AA_QEC_MEAS_TIME_1: 0.090s (= 6 *$AA_QEC_TIME_1)
– $AA_QEC_MEAS_TIME_2: 0.045s (= 3 * $AA_QEC_TIME_1)
– $AA_QEC_MEAS_TIME_3: 0.030s (= 2 * $AA_QEC_TIME_1)
The recommended values must only be changed if the compensation is insufficient in
these acceleration ranges or if $AA_QEC_TIME_1 is changed. For further information,
please refer to Section "Further optimization and intervention options".
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
Extended Functions