notch_filter.h File Reference

Second order notch filter. More...

#include "std.h"

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Data Structures
struct	SecondOrderNotchFilter

Functions
static void	notch_filter_set_sampling_frequency (struct SecondOrderNotchFilter *filter, uint16_t frequency)
	Set sampling frequency of the notch filter. More...
static void	notch_filter_set_bandwidth (struct SecondOrderNotchFilter *filter, float bandwidth)
	Set bandwidth of the notch filter. More...
static void	notch_filter_set_filter_frequency (struct SecondOrderNotchFilter *filter, float frequency)
	Set notch filter frequency in Hz. More...
static void	notch_filter_update (struct SecondOrderNotchFilter *filter, int32_t *input_signal, int32_t *output_signal)
	Notch filter propagate. More...
static int32_t	notch_filter_get_output (struct SecondOrderNotchFilter *filter)
	Get latest notch filter output. More...
static void	notch_filter_init (struct SecondOrderNotchFilter *filter, float cutoff_frequency, float bandwidth, uint16_t sample_frequency)
	Initialize second order notch filter. More...

Detailed Description

Second order notch filter.

Definition in file notch_filter.h.

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Data Structure Documentation

SecondOrderNotchFilter

struct SecondOrderNotchFilter

Definition at line 32 of file notch_filter.h.

Data Fields
float	costheta
float	d2
float	Ts
int32_t	xn1
float	xn1
int32_t	xn2
float	xn2
int32_t	yn1
float	yn1
int32_t	yn2
float	yn2

Function Documentation

notch_filter_get_output()

static int32_t notch_filter_get_output ( struct SecondOrderNotchFilter *  filter )

inlinestatic

Get latest notch filter output.

Parameters

filter

filter data structure

Returns

Latest filtered value

Definition at line 105 of file notch_filter.h.

References SecondOrderNotchFilter::yn1.

notch_filter_init()

static void notch_filter_init ( struct SecondOrderNotchFilter *  filter, float  cutoff_frequency, float  bandwidth, uint16_t  sample_frequency  )

inlinestatic

Initialize second order notch filter.

Discrete implementation: y[n] = b * y[n-1] - d^2 * y[n-2] + a * x[n] - b * x[n-1] + a * x[n-2]

Parameters

cutoff_frequency	frequency to attenuate [Hz]
bandwidth	bandwidth of the filter [Hz]
sample_frequency	frequency at which the filter is updated

Definition at line 119 of file notch_filter.h.

References notch_filter_set_bandwidth(), notch_filter_set_filter_frequency(), notch_filter_set_sampling_frequency(), SecondOrderNotchFilter::xn1, SecondOrderNotchFilter::xn2, SecondOrderNotchFilter::yn1, and SecondOrderNotchFilter::yn2.

Referenced by adaptive_notch_filter_init(), init_filter(), and stabilization_attitude_heli_indi_init().

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notch_filter_set_bandwidth()

static void notch_filter_set_bandwidth ( struct SecondOrderNotchFilter *  filter, float  bandwidth  )

inlinestatic

Set bandwidth of the notch filter.

Parameters

filter	filter data structure
bandwidth	bandwidth of the filter [Hz]

Definition at line 57 of file notch_filter.h.

References SecondOrderNotchFilter::d2, and SecondOrderNotchFilter::Ts.

Referenced by notch_filter_init().

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notch_filter_set_filter_frequency()

static void notch_filter_set_filter_frequency ( struct SecondOrderNotchFilter *  filter, float  frequency  )

inlinestatic

Set notch filter frequency in Hz.

Parameters

filter	filter data structure
frequency	to attenuate [Hz]

Definition at line 68 of file notch_filter.h.

References SecondOrderNotchFilter::costheta, and SecondOrderNotchFilter::Ts.

Referenced by adaptive_notch_filter_update(), indi_apply_notch_filters(), and notch_filter_init().

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notch_filter_set_sampling_frequency()

static void notch_filter_set_sampling_frequency ( struct SecondOrderNotchFilter *  filter, uint16_t  frequency  )

inlinestatic

Set sampling frequency of the notch filter.

Parameters

filter	filter data structure
frequency	frequency at which the filter is updated

Definition at line 47 of file notch_filter.h.

References SecondOrderNotchFilter::Ts.

Referenced by notch_filter_init().

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notch_filter_update()

static void notch_filter_update ( struct SecondOrderNotchFilter *  filter, int32_t *  input_signal, int32_t *  output_signal  )

inlinestatic

Notch filter propagate.

Discrete implementation: y[n] = b * y[n-1] - d^2 * y[n-2] + a * x[n] - b * x[n-1] + a * x[n-2]

Parameters

filter	filter data structure
input_signal	input x[n]
output_signal	output y[n]

Definition at line 83 of file notch_filter.h.

References b, SecondOrderNotchFilter::costheta, SecondOrderNotchFilter::d2, SecondOrderNotchFilter::xn1, SecondOrderNotchFilter::xn2, SecondOrderNotchFilter::yn1, and SecondOrderNotchFilter::yn2.

Referenced by adaptive_notch_filter_update(), indi_apply_notch_filters(), and oneloop_andi_propagate_filters().

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