Implementation of complementary filters (first order, second order, and Butterworth variants) More...

#include "std.h"
#include "filters/low_pass_filter.h"

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Data Structures
struct	FirstOrderComplementary
	First order complementary filter structure. More...

struct	SecondOrderComplementary
	Second order complementary filter structure. More...

struct	Butterworth4Complementary
	4th order Butterworth complementary filter structure. More...

Typedefs
typedef struct SecondOrderComplementary	Butterworth2Complementary

Functions
static void	init_first_order_complementary (struct FirstOrderComplementary *filter, float cut_off, float sample_time, float value)
	Initialize the first order complementary filter.

static float	update_first_order_complementary (struct FirstOrderComplementary *filter, float value_x, float value_y)
	Update the first order complementary filter with new input values.

static float	reset_first_order_complementary (struct FirstOrderComplementary *filter, float value)
	Reset the first order complementary filter to a specific value.

static float	get_first_order_complementary (const struct FirstOrderComplementary *filter)
	Get current value of the first order complementary filter.

static void	init_second_order_complementary (struct SecondOrderComplementary *filter, float cut_off, float Q, float sample_time, float value)
	Initialize the second order complementary filter.

static float	update_second_order_complementary (struct SecondOrderComplementary *filter, float value_x, float value_y)
	Update the second order complementary filter with new input values.

static float	reset_second_order_complementary (struct SecondOrderComplementary *filter, float value)
	Reset the second order complementary filter to a specific value.

static float	get_second_order_complementary (const struct SecondOrderComplementary *filter)
	Get current value of the second order complementary filter.

static void	init_butterworth_2_complementary (Butterworth2Complementary *filter, float cut_off, float sample_time, float value)
	Initialize the Butterworth 2nd order low-pass complementary filter.

static float	update_butterworth_2_complementary (Butterworth2Complementary *filter, float value_x, float value_y)
	Update the Butterworth 2nd order low-pass complementary filter with new input values.

static void	reset_butterworth_2_complementary (Butterworth2Complementary *filter, float value)
	Reset the Butterworth 2nd order complementary filter to a specific value.

static float	get_butterworth_2_complementary (const Butterworth2Complementary *filter)
	Get current value of the Butterworth 2nd order low-pass complementary filter.

static void	init_butterworth_4_complementary (Butterworth4Complementary *filter, float cut_off, float sample_time, float value)
	Initialize the Butterworth 4th order low-pass complementary filter.

static float	update_butterworth_4_complementary (Butterworth4Complementary *filter, float value_x, float value_y)
	Update the Butterworth 4th order low-pass complementary filter with new input values.

static void	reset_butterworth_4_complementary (Butterworth4Complementary *filter, float value)
	Reset the Butterworth 4th order complementary filter to a specific value.

static float	get_butterworth_4_complementary (const Butterworth4Complementary *filter)
	Get current value of the Butterworth 4th order low-pass complementary filter.

Detailed Description

Implementation of complementary filters (first order, second order, and Butterworth variants)

Provides structures and functions to initialize, update, reset, and get outputs from first order and second order complementary filters, as well as Butterworth complementary filters.

FIXME: This implementation of complementary filters forces user to first integrate or differentiate the signals outside of the filter before passing them in. Consider extending the filter to handle integration and differentiation internally. Maybe implement cascaded complementary filters for this purpose.

Author: Justin Dubois j.p.g.nosp@m..dub.nosp@m.ois@s.nosp@m.tude.nosp@m.nt.tu.nosp@m.delf.nosp@m.t.nl

Definition in file complementary_filter.h.

Data Structure Documentation

◆ FirstOrderComplementary

struct FirstOrderComplementary

First order complementary filter structure.

This structure contains two first order low-pass filters, one for the high-pass path and one for the low-pass path.

Definition at line 49 of file complementary_filter.h.

Collaboration diagram for FirstOrderComplementary:

Data Fields
struct FirstOrderLowPass	x_lp_filter
struct FirstOrderLowPass	y_lp_filter

◆ SecondOrderComplementary

struct SecondOrderComplementary

Second order complementary filter structure.

This structure contains two second order low-pass filters, one for the high-pass path and one for the low-pass path.

Definition at line 118 of file complementary_filter.h.

Collaboration diagram for SecondOrderComplementary:

Data Fields
struct SecondOrderLowPass	x_lp_filter
struct SecondOrderLowPass	y_lp_filter

◆ Butterworth4Complementary

struct Butterworth4Complementary

4th order Butterworth complementary filter structure.

This structure contains two 4th order Butterworth low-pass filters, one for the high-pass path and one for the low-pass path.

Definition at line 243 of file complementary_filter.h.

Collaboration diagram for Butterworth4Complementary:

Data Fields
Butterworth4LowPass	x_lp_filter
Butterworth4LowPass	y_lp_filter

Typedef Documentation

◆ Butterworth2Complementary

typedef struct SecondOrderComplementary Butterworth2Complementary

Definition at line 184 of file complementary_filter.h.

Function Documentation

◆ get_butterworth_2_complementary()

static float get_butterworth_2_complementary ( const Butterworth2Complementary * filter )

inlinestatic

Get current value of the Butterworth 2nd order low-pass complementary filter.

Parameters

filter Complementary filter struct

Returns: Current output value of the filter

Definition at line 232 of file complementary_filter.h.

References get_second_order_complementary().

Referenced by get_butterworth_2_complementary_array(), get_butterworth_2_complementary_rates(), and get_butterworth_2_complementary_vect3().

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◆ get_butterworth_4_complementary()

static float get_butterworth_4_complementary ( const Butterworth4Complementary * filter )

inlinestatic

Get current value of the Butterworth 4th order low-pass complementary filter.

Parameters

filter Complementary filter struct

Returns: Current output value of the filter

Definition at line 293 of file complementary_filter.h.

References foo, get_butterworth_4_low_pass(), SecondOrderLowPass::i, Butterworth4LowPass::lp1, Butterworth4Complementary::x_lp_filter, and Butterworth4Complementary::y_lp_filter.

Referenced by get_butterworth_4_complementary_array(), get_butterworth_4_complementary_rates(), and get_butterworth_4_complementary_vect3().

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◆ get_first_order_complementary()

static float get_first_order_complementary ( const struct FirstOrderComplementary * filter )

inlinestatic

Get current value of the first order complementary filter.

Parameters

filter Complementary filter struct

Returns: Current output value of the filter

Definition at line 105 of file complementary_filter.h.

References foo, get_first_order_low_pass(), FirstOrderLowPass::last_in, FirstOrderComplementary::x_lp_filter, and FirstOrderComplementary::y_lp_filter.

Referenced by get_first_order_complementary_array(), get_first_order_complementary_rates(), and get_first_order_complementary_vect3().

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◆ get_second_order_complementary()

static float get_second_order_complementary ( const struct SecondOrderComplementary * filter )

inlinestatic

Get current value of the second order complementary filter.

Parameters

filter Complementary filter struct

Returns: Current output value of the filter

Definition at line 177 of file complementary_filter.h.

References foo, get_second_order_low_pass(), SecondOrderLowPass::i, SecondOrderComplementary::x_lp_filter, and SecondOrderComplementary::y_lp_filter.

Referenced by get_butterworth_2_complementary().

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◆ init_butterworth_2_complementary()

static void init_butterworth_2_complementary	(	Butterworth2Complementary *	filter,
		float	cut_off,
		float	sample_time,
		float	value
	)

inlinestatic

Initialize the Butterworth 2nd order low-pass complementary filter.

Parameters

filter	Complementary filter struct
cut_off	Time constant of the low-pass filter
sample_time	Sampling period
value	Initial value for filter history

Definition at line 193 of file complementary_filter.h.

References foo, and init_second_order_complementary().

Referenced by init_butterworth_2_complementary_array(), and init_butterworth_2_complementary_vect3().

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◆ init_butterworth_4_complementary()

static void init_butterworth_4_complementary	(	Butterworth4Complementary *	filter,
		float	cut_off,
		float	sample_time,
		float	value
	)

inlinestatic

Initialize the Butterworth 4th order low-pass complementary filter.

Parameters

filter	Complementary filter struct
cut_off	Time constant of the low-pass filter
sample_time	Sampling period
value	Initial value for filter history

Definition at line 255 of file complementary_filter.h.

References foo, init_butterworth_4_low_pass(), Butterworth4Complementary::x_lp_filter, and Butterworth4Complementary::y_lp_filter.

Referenced by init_butterworth_4_complementary_array(), and init_butterworth_4_complementary_vect3().

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◆ init_first_order_complementary()

static void init_first_order_complementary	(	struct FirstOrderComplementary *	filter,
		float	cut_off,
		float	sample_time,
		float	value
	)

inlinestatic

Initialize the first order complementary filter.

Parameters

filter	Complementary filter struct
cut_off	Time constant of the low-pass filter
sample_time	Sampling period
value	Initial value for filter history

Definition at line 61 of file complementary_filter.h.

References foo, init_first_order_low_pass(), FirstOrderComplementary::x_lp_filter, and FirstOrderComplementary::y_lp_filter.

Referenced by init_first_order_complementary_array(), and init_first_order_complementary_vect3().

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◆ init_second_order_complementary()

static void init_second_order_complementary	(	struct SecondOrderComplementary *	filter,
		float	cut_off,
		float	Q,
		float	sample_time,
		float	value
	)

inlinestatic

Initialize the second order complementary filter.

Parameters

filter	Complementary filter struct
cut_off	Time constant of the low-pass filter
Q	Q factor of the low-pass filter
sample_time	Sampling period
value	Initial value for filter history