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.

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Detail View

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

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Detail View



  • s - Laplace-domain frequency parameter

  • fc - Cutoff frequency of the low-pass filter or central frequency of the Notch filter, defined in Radians/s 1

  • fw - Full width of the rejection band of the Notch filter [fc - fw /2 ,fc + fw/2], defined in Radians/s 1

  • {\zeta} - damping ratio


Radians are used for internal calculation, user input is in [Hz]

Low-pass filter

Torque loop input shaping filter


The following equation was used to design the torque loop input shaping filter:

BS2(s) =  \frac {s^2 +f_c^2} {s + f_w s + f_c^2}


Cut-off frequency of velocity feedback filter

Cut-off frequency of position feedback filter

Center frequency and bandwidth of notch filter