Description

The filter algorithms that are implemented in the controller are characterized by high selectivity with a low order of the filter. For each specific axis, the properties of the filters used can be defined via the axis parameter record. A filter's behavior is essentially defined by the type of the filter prototype P-AXIS-00153, the filter type P-AXIS-00204, its order P-AXIS-00140 and its characteristic frequency P-AXIS-00067. For certain filter types, the quality P-AXIS-00080 is also a defining attribute.

In the case of a standard filter (exception: HSC filter), up to three filters can be defined for each axis that are then connected in series.

Filter types

Filters can be classified according to their characteristic transmission behavior and thus their purpose. The filter types with the following characteristics can be used

The filter types listed below are standard filters.

• Low-pass filters
  All frequencies below a certain cut-off frequency are passed through the filter. Higher frequencies above this cut-off frequency are attenuated or are no longer passed through at all. The high frequencies are filtered out.
• High-pass filters
  The low frequencies of a signal are attenuated or are not passed through at all. Only as from a cut-off frequency are the frequencies transmitted without modification.
• Band-stop filters
  One frequency range out of the frequency spectrum to be transmitted is filtered out. All other frequencies are transmitted almost without damping. The characteristic frequency is called the center frequency.
• Band-pass filters
  All frequencies except for the chosen frequency band are filtered out. All other frequencies are attenuated.
• All-pass filters
  These filters have a constant gain, but generate a frequency-dependent phase shift. They are used for phase correction and to delay signals.
• PT1 filters
  A PT1 filter is a delay element of the first order that has a transmission response similar to that of a low-pass filter of the first order. The filter transmits frequencies under the
  cut-off frequency fg = 1 / (2 * Pi * P-AXIS-00357). Frequencies higher than the cut-off frequency are attenuated with–20dB/decade.

The following filter types are only to be used in conjunction with the prototype HSC.

• HSC-Sinc
  The HSC-Sinc filter is an acausal time range filter with a sin(x)/x profile. Its effect in the frequency band is that of a low-pass filter.
• HSC-average
  The HSC average filter is an acausal time range average filter. Its effect in the frequency band is that of a low-pass filter.
• HSC-Gauss
  The HSC Gauss filter is an acausal time range filter with a Gaussian curve profile. Its effect in the frequency band is that of a low-pass filter.

Filter prototypes

Five different prototypes of filters can be selected. They are essentially distinguished by their behavior when transmitting frequencies and their response to abrupt change of command value(step response of the filter).

These are

• Filter with critical damping
• Bessel filter
• Butterworth filter
• Chebyshev filter
• HSC