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.
The position feedback filter can also be used with a simple PID loop:
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
- damping ratio
The following equation was used to design the torque loop input shaping filter:
Cut-off frequency of velocity feedback filter
Cut-off frequency of position feedback filter
Center frequency and bandwidth of notch filter