1104 HEIDENHAIN Technical Manual iTNC 530 HSCI
7.7.7 Crossover Position Filter (CPF)
The CPF can be used only in dual-encoder systems with rotary encoder and
position encoder. In such systems, the CPF is used to passively dampen
certain machine vibrations caused by the drive components in the drive chain.
In order to stabilize the position control loop in such systems with resonances,
the position signal from the position encoder, which is filtered through a low-
pass filter, and the position signal from the motor speed encoder, which is
filtered through a high-pass filter, are added and made available to the position
controller as actual position value. The filter frequency (separation frequency)
is set in MP2609 for this. The typical filter frequency values in MP2609 are
between 20 Hz and 80 Hz.
The separation frequency can be determined with the position-controller Bode
diagram of the TNCopt PC tool. The frequency at which an excessive
resonance occurs is to be selected as the value for MP2609. After the
separation frequency has been defined, the kV factor can be increased.
The block diagram shows how the crossover position filter works:
1: Crossover position filter (CPF) with high-pass (HP) and low-pass (LP)
2: Position controller
3: Speed controller
4: Current controller – power module
5: Motor
6: Machine
7: Linear encoder
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