“DIRECT" mode

“DIRECT" mode (P-AXIS-00753) only uses direct measured values to dampen vibrations; the vibrations to be damped (P-AXIS-00751) must therefore be contained in the actual values.

The figure below shows the extension of the PPI cascade rule for “DIRECT" mode:

Ideally, frequencies to be damped are included in speed values from v_ist2 and are recorded by a direct measuring system. The measured frequency range is reduced to the relevant frequency by using a suitable band-pass filter. After scaling the results, an additional additive speed (v_{add_ges}) is added to the manipulated variable of the position controller (v_soll) This results in a counter-motion of the motor to compensate for a particular vibration.

If no direct measuring system is installed, the actual values of the motor (v_ist1) can be used as an alternative, provided the vibration is visible in the actual speed of the motor encoder (v_ist1).

Attention

Excessive scaling of the additive speed may cause the motor to vibrate.

Consequence: The control loop becomes unstable.