Filtering¶

Overview¶

Attention

Since Firmware 5.0 only 1st order Position and Velocity Feedback filters are supported.

A digital filter removes unwanted components from the signal which passes through it.

This feature can be used for example as:

Position Feedback filter - Reduce encoder noise. A 1st order low-pass filter is supported.
Velocity feedback filter - Reduce noise and effects of encoder nonlinearity in the velocity signal. A 1st order low-pass filter is supported.
Loop shaping filter - Suppress excitation of resonance frequencies in the output of the motion control loop or in the input of the torque control loop. A 2nd order notch filter is supported.

Any signal can be decomposed into a sum of sine waves with different frequencies. Some of them might negatively affect the control loops. It is possible to attenuate these unwanted frequencies by properly configuring a corresponding filter.

Configurable filters are implemented for the signals that are considered the most important for motion control.

General ViewDetail ViewGeneral View

../../../../../_images/control_filters2.png

Detail View

../../../../../_images/control_filters_objects2.png

The position feedback filter can also be used with a simple PID loop:

General ViewDetail ViewGeneral View

../../../../../_images/control_filters_simple2.png

Detail View

../../../../../_images/control_filters_simple_objects2.png

Methods¶

Definitions¶

s - Laplace-domain frequency parameter
f_c - Cutoff frequency of the low-pass filter or central frequency of the Notch filter, defined in Radians/s 1
f_w - Full width of the rejection band of the Notch filter [f_c - f_w /2 ,f_c + f_w/2], defined in Radians/s 1
${\zeta}$ - damping ratio