Plausibility Check For Absolute Encoders - Siemens SINUMERIK 840D sl Function Manual

A3: Axis Monitoring, Protection Zones
3.2 Axis monitoring functions
Fault
Upon exceeding of the encoder limit frequency, the following occurs:
● Message to the PLC:
DB31, ... DBX60.2 or 60.3 = 1 (encoder limit frequency exceeded 1 or 2)
● Spindles
Spindles are not stopped but continue to turn with speed control.
If the spindle speed is reduced so much that the encoder frequency passes below the
encoder limit frequency, the actual value system of the spindle is automatically
resynchronized.
● Axes
The following alarm is displayed:
21610 "Channel <Channel number> Axis <Axis name> Encoder <Encoder number >
Frequency exceeded"
The affected axis is stopped via the configured braking ramp in follow-up mode:
MD36610 $MA_AX_EMERGENCY_STOP_TIME
(maximum time for braking ramp when an error occurs)
Note
If the encoder limit frequency is exceeded, a position-controlled machine axis must be re-
referenced (see Section "R1: Referencing (Page 1149)").
3.2.5.2

Plausibility check for absolute encoders

Function
With absolute encoders (MD30240 $MA_ENC_TYPE = 4), absolute values supplied by the
measuring system are used to check the plausibility of the actual value.
During the check, the NC compares the cyclic position value held in the position control cycle
clock based on the incremental information from the encoder with a new position value
generated directly from the absolute and incremental information and checks that the
calculated position difference does not exceed the permissible deviation.
MD36310 $MA_ENC_ZERO_MONITORING (permissible deviation in 1/2 coarse increments
between the absolute and the incremental encoder track)
Note
The plausibility check of absolute encoders specifically detects all deviations caused by dirt
on the absolute track or by faults when transferring the absolute value. However, small errors
in the incremental track (burst interference, impulse errors) are not detected. In such instances
the plausibility check only responds to deviations in the millimeter range. This form of
monitoring should therefore serve as additional monitoring to assist the diagnosis of absolute-
position faults.
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Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Basic Functions