Bosch Rexroth IndraDrive MPH-02 Functional Description page 267

MPH-02, MPB-02, MPD-02
Description of Filter Function
Filtering by Means of Multiple
Smoothing Filter
DOK-INDRV*-MP*-02VRS**-FK01-EN-P
For each filter it is possible to set center frequency and bandwidth. The
attenuation of the rejection frequency is the strongest; the bandwidth
determines the frequency range in which the attenuation is smaller than –
3 dB.
Note: Due to the filter structure, greater bandwidth results in lower
attenuation of the rejection frequency!
attenuation in dB
0
-3
P-0-1123 center frequency
Fig. 6-38: Amplitude characteristic of a band-stop filter depending on the
bandwidth (qualitative)
Optimizing the control loop by means of a rejection filter does not always
sufficiently improve the quality of control. This is the case, for example,
when the closed control loop has no distinctive resonance frequencies or
when there are more than 4 resonance points. It is then possible to obtain
the desired quality of control by activating several smoothing filters (with
PT2 characteristics).
To do this, each of the 4 elements in parameter P-0-1120, Velocity
control loop filter: filter type is set to the value "1" or "0" (see
Parameter Description of P-0-1120).
Instead of the rejection filter there are smoothing filters activated in the
control loop the smoothing time constants (T
parameter P-0-1121, Velocity control loop filter: limit frequency of
low pass.
Together with the PT1-filter (P-0-0004, Velocity loop smoothing time
constant) at the velocity loop input you obtain a filter characteristics with
PT -behavior. Frequencies higher than the limit frequency (f
N
are suppressed much more and cannot excite the control loop oscillation.
The following applies to the filter effect:
• P-0-0004, Velocity loop smoothing time constant
→ attenuation of 20 dB/decade
• P-0-1121, Velocity control loop filter: limit frequency of low pass
→ attenuation of 40 dB/decade
When activating all low-pass filters the maximum attenuation is
180 dB/decade. This is a very high filter degree.
Drive Control
P-0-1122
bandwidth
) of which are contained in
gl
6-55
frequency f
Sv5052f1.fh7
= 1/2πT )
g gl