Bosch Rexroth IndraDrive MPH-02 Functional Description page 555

MPH-02, MPB-02, MPD-02
Oscillating Signal Frequency
within one Output Cycle
Display Limits
Beat Effects in the Emulated
Position
DOK-INDRV*-MP*-02VRS**-FK01-EN-P
Due to the internal signal processing, the periodic time and duty cycle of
the output signals are varying. The periodic time (or frequency) of the
resulting cycles can therefore be shorter or longer, too.
This is why the signals of incremental emulation should not be used for
measuring the speed by means of frequency measurement, but the
signals may only be evaluated by counting the increments.
Restrictions of Absolute Encoder Emulation
Using absolute encoder
4096 revolutions in absolute form.
When using this kind of emulation at the display limits, small fluctuations
of the actual position lead to overflow and a position jump in the emulated
position.
This is the case, for example, at position 0 and 4096 revolutions after
position zero.
emulated
position jump
position
0 2048
S-0-0052, Reference distance 1
Fig. 9-14: Display limits with absolute encoder emulation
This effect can be avoided by shifting the home point by executing
P-0-0012, C0300 Command Set absolute measuring.
Note: By the respective setting in parameter S-0-0052, Reference
distance 1 shift the reference position to the middle of the
display range. This allows moving 2048 revolutions to the left
and to the right.
In case the position processing in the control unit and the position
detection (sampling) in the drive are not synchronized, beat effects can
occur in the emulated signal with a periodic time according to the formula
below, if the quartz frequencies on the drive and in the control unit cannot
be exactly (integrally) divided:
∆f:
frequency deviation of the quartzes in control unit and drives
T: periodic time for the occurring beat frequency
Fig. 9-15: Determining the periodic time
Extended Drive Functions
emulation, it is possible
4096 motor position in
home point
1
= ∆ =
T t
∆
f
9-27
to display
revolutions
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