high_pass_filter.h File Reference

Simple high pass filter with double precision. More...

#include "std.h"
#include "math/pprz_algebra_int.h"

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Data Structures
struct	FirstOrderHighPass
	First order high pass filter structure. More...
struct	FourthOrderHighPass
	Fourth order filter structure. More...

Functions
static void	init_first_order_high_pass (struct FirstOrderHighPass *filter, float tau, float sample_time, float value)
	Init first order high pass filter. More...
static float	update_first_order_high_pass (struct FirstOrderHighPass *filter, float value)
	Update first order high pass filter state with a new value. More...
static float	get_first_order_high_pass (struct FirstOrderHighPass *filter)
	Get current value of the first order high pass filter. More...
static void	init_fourth_order_high_pass (struct FourthOrderHighPass *filter, double *a, double *b, double value)
	Init fourth order high pass filter. More...
static double	update_fourth_order_high_pass (struct FourthOrderHighPass *filter, double value)
	Update fourth order high pass filter state with a new value. More...
static double	get_fourth_order_high_pass (struct FourthOrderHighPass *filter)
	Get current value of the fourth order high pass filter. More...

Detailed Description

Simple high pass filter with double precision.

Definition in file high_pass_filter.h.

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Data Structure Documentation

FirstOrderHighPass

struct FirstOrderHighPass

First order high pass filter structure.

using bilinear z transform

Definition at line 37 of file high_pass_filter.h.

Data Fields
float	last_in
float	last_out
float	time_const

FourthOrderHighPass

struct FourthOrderHighPass

Fourth order filter structure.

Polynomial discrete form:

   b0 + b1 z^-1 + b2 z^-2 etc

H(z) = -------------------— a0 + a1 z^-1 + a2 z^-2 etc

Definition at line 99 of file high_pass_filter.h.

Data Fields
double	a[4]	denominator gains
double	b[4]	numerator gains
double	i[4]	input history
double	o[4]	output history

Function Documentation

get_first_order_high_pass()

static float get_first_order_high_pass ( struct FirstOrderHighPass *  filter )

inlinestatic

Get current value of the first order high pass filter.

Parameters

filter

first order high pass filter structure

Returns

current value of the filter

Definition at line 86 of file high_pass_filter.h.

References FirstOrderHighPass::last_out.

get_fourth_order_high_pass()

static double get_fourth_order_high_pass ( struct FourthOrderHighPass *  filter )

inlinestatic

Get current value of the fourth order high pass filter.

Parameters

filter

fourth order high pass filter structure

Returns

current value of the filter

Definition at line 159 of file high_pass_filter.h.

References FourthOrderHighPass::o.

init_first_order_high_pass()

static void init_first_order_high_pass ( struct FirstOrderHighPass *  filter, float  tau, float  sample_time, float  value  )

inlinestatic

Init first order high pass filter.

Laplace transform in continuous time: tau*s H(s) = ------— 1 + tau*s

Parameters

filter	first order high pass filter structure
tau	time constant of the first order high pass filter
sample_time	sampling period of the signal
value	initial value of the filter

Definition at line 56 of file high_pass_filter.h.

References FirstOrderHighPass::last_in, FirstOrderHighPass::last_out, and FirstOrderHighPass::time_const.

Referenced by nps_fdm_init().

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init_fourth_order_high_pass()

static void init_fourth_order_high_pass ( struct FourthOrderHighPass *  filter, double *  a, double *  b, double  value  )

inlinestatic

Init fourth order high pass filter.

Parameters

filter	fourth order high pass filter structure
value	initial value of the filter

Definition at line 112 of file high_pass_filter.h.

References FourthOrderHighPass::a, FourthOrderHighPass::b, b, FourthOrderHighPass::i, and FourthOrderHighPass::o.

update_first_order_high_pass()

static float update_first_order_high_pass ( struct FirstOrderHighPass *  filter, float  value  )

inlinestatic

Update first order high pass filter state with a new value.

Parameters

filter	first order high pass filter structure
value	new input value of the filter

Returns

new filtered value

Definition at line 70 of file high_pass_filter.h.

References FirstOrderHighPass::last_in, FirstOrderHighPass::last_out, and FirstOrderHighPass::time_const.

Referenced by gazebo_write().

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update_fourth_order_high_pass()

static double update_fourth_order_high_pass ( struct FourthOrderHighPass *  filter, double  value  )

inlinestatic

Update fourth order high pass filter state with a new value.

Parameters

filter	fourth order high pass filter structure
value	new input value of the filter

Returns

new filtered value

Definition at line 131 of file high_pass_filter.h.

References FourthOrderHighPass::a, FourthOrderHighPass::b, FourthOrderHighPass::i, and FourthOrderHighPass::o.