Man page - lowpass(9)

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Manual

LOWPASS

NAME
SYNOPSIS
FUNCTIONS
PINS
PARAMETERS
NOTES
AUTHOR
LICENSE

NAME

lowpass - Low-pass filter

SYNOPSIS

loadrt lowpass [count= N |names= name1 [, name2... ]]

FUNCTIONS

lowpass. N (requires a floating-point thread)

PINS

lowpass. N .in float in
lowpass. N .out float out

out += (in - out) * gain

lowpass. N .load bit in

When TRUE, copy in to out instead of applying the filter equation.

PARAMETERS

lowpass. N .gain float rw

NOTES

gain pin setting

The digital filter implemented is equivalent to a unity-gain continuous-time single-pole low-pass filter that is preceded by a zero-order-hold and sampled at a fixed period. For a pole at -a (radians/seconds) the corresponding continuous-time lowpass filter LaPlace transfer function is:

H(s) = a/(s + a)

For a sampling period T (seconds), the gain for this Hal lowpass component is:

gain = 1 - eˆ(-a * T)

e = 2.71828 https://en.wikipedia.org/wiki/E_(mathematical_constant)

Examples:
T = 0.001 seconds (typical servo thread period)
a = (2*pi*100) ( 100Hz bandwidth single pole)
gain = 0.466

T = 0.001 seconds (typical servo thread period)
a = (2*pi*10) ( 10Hz bandwidth single pole)
gain = 0.0609

T = 0.001 seconds (typical servo thread period)
a = (2*pi*1) ( 1Hz bandwidth single pole)
gain = 0.0063

AUTHOR

Jeff Epler

LICENSE

GPL