Filter: add comments and address review comments for harmonic notch

This commit is contained in:
Andy Piper 2019-08-28 21:18:00 +01:00 committed by Andrew Tridgell
parent 6ddaf81439
commit 334ebadd5a
2 changed files with 65 additions and 33 deletions

View File

@ -22,47 +22,47 @@
const AP_Param::GroupInfo HarmonicNotchFilterParams::var_info[] = {
// @Param: ENABLE
// @DisplayName: Enable
// @Description: Enable harmonic notch filter
// @DisplayName: Harmonic Notch Filter enable
// @Description: Harmonic Notch Filter enable
// @Values: 0:Disabled,1:Enabled
// @User: Advanced
AP_GROUPINFO_FLAGS("ENABLE", 1, HarmonicNotchFilterParams, _enable, 0, AP_PARAM_FLAG_ENABLE),
// @Param: FREQ
// @DisplayName: Base Frequency
// @Description: Notch base center frequency in Hz
// @DisplayName: Harmonic Notch Filter base frequency
// @Description: Harmonic Notch Filter base center frequency in Hz
// @Range: 10 400
// @Units: Hz
// @User: Advanced
AP_GROUPINFO("FREQ", 2, HarmonicNotchFilterParams, _center_freq_hz, 80),
// @Param: BW
// @DisplayName: Bandwidth
// @Description: Harmonic notch bandwidth in Hz
// @DisplayName: Harmonic Notch Filter bandwidth
// @Description: Harmonic Notch Filter bandwidth in Hz
// @Range: 5 100
// @Units: Hz
// @User: Advanced
AP_GROUPINFO("BW", 3, HarmonicNotchFilterParams, _bandwidth_hz, 20),
// @Param: ATT
// @DisplayName: Attenuation
// @Description: Harmonic notch attenuation in dB
// @DisplayName: Harmonic Notch Filter attenuation
// @Description: Harmonic Notch Filter attenuation in dB
// @Range: 5 30
// @Units: dB
// @User: Advanced
AP_GROUPINFO("ATT", 4, HarmonicNotchFilterParams, _attenuation_dB, 15),
// @Param: HMNCS
// @DisplayName: Harmonics
// @Description: Bitmask of harmonic frequencies to apply notches to. This option takes effect on the next reboot. A maximum of 3 harmonics can be used at any one time
// @DisplayName: Harmonic Notch Filter harmonics
// @Description: Bitmask of harmonic frequencies to apply Harmonic Notch Filter to. This option takes effect on the next reboot. A maximum of 3 harmonics can be used at any one time
// @Bitmask: 0:1st harmonic,1:2nd harmonic,2:3rd harmonic,3:4th hamronic,4:5th harmonic,5:6th harmonic,6:7th harmonic,7:8th harmonic
// @User: Advanced
// @RebootRequired: True
AP_GROUPINFO("HMNCS", 5, HarmonicNotchFilterParams, _harmonics, 3),
// @Param: REF
// @DisplayName: Reference value
// @Description: Reference value associated with the specified frequency to facilitate frequency scaling
// @DisplayName: Harmonic Notch Filter reference value
// @Description: Reference value associated with the specified frequency to facilitate frequency scaling of the Harmonic Notch Filter
// @User: Advanced
// @Range: 0.1 0.9
// @RebootRequired: True
@ -71,9 +71,18 @@ const AP_Param::GroupInfo HarmonicNotchFilterParams::var_info[] = {
AP_GROUPEND
};
/*
destroy all of the associated notch filters
*/
template <class T>
HarmonicNotchFilter<T>::~HarmonicNotchFilter() {
delete[] _filters;
_num_filters = 0;
}
/*
initialise filter
initialise the associated filters with the provided shaping constraints
the constraints are used to determine attenuation (A) and quality (Q) factors for the filter
*/
template <class T>
void HarmonicNotchFilter<T>::init(float sample_freq_hz, float center_freq_hz, float bandwidth_hz, float attenuation_dB)
@ -87,8 +96,10 @@ void HarmonicNotchFilter<T>::init(float sample_freq_hz, float center_freq_hz, fl
// adjust the center frequency to be in the allowable range
center_freq_hz = constrain_float(center_freq_hz, bandwidth_hz * 0.52f, sample_freq_hz * 0.48f);
// calculate attenuation and quality from the shaping constraints
NotchFilter<T>::calculate_A_and_Q(center_freq_hz, bandwidth_hz, attenuation_dB, _A, _Q);
// initialize all the configured filters with the same A & Q and multiples of the center frequency
for (uint8_t i = 0, filt = 0; i < HNF_MAX_HARMONICS && filt < _num_filters; i++) {
if ((1U<<i) & _harmonics) {
_filters[filt++].init_with_A_and_Q(sample_freq_hz, center_freq_hz * (i+1), _A, _Q);
@ -98,10 +109,10 @@ void HarmonicNotchFilter<T>::init(float sample_freq_hz, float center_freq_hz, fl
}
/*
initialise filter
allocate a collection of, at most HNF_MAX_FILTERS, notch filters to be managed by this harmonic notch filter
*/
template <class T>
void HarmonicNotchFilter<T>::create(uint8_t harmonics)
void HarmonicNotchFilter<T>::allocate_filters(uint8_t harmonics)
{
for (uint8_t i = 0; i < HNF_MAX_HARMONICS && _num_filters < HNF_MAX_FILTERS; i++) {
if ((1U<<i) & harmonics) {
@ -114,13 +125,10 @@ void HarmonicNotchFilter<T>::create(uint8_t harmonics)
_harmonics = harmonics;
}
template <class T>
HarmonicNotchFilter<T>::~HarmonicNotchFilter() {
if (_num_filters > 0) {
delete[] _filters;
}
}
/*
update the underlying filters' center frequency using the current attenuation and quality
this function is cheaper than init() because A & Q do not need to be recalculated
*/
template <class T>
void HarmonicNotchFilter<T>::update(float center_freq_hz)
{
@ -131,6 +139,7 @@ void HarmonicNotchFilter<T>::update(float center_freq_hz)
// adjust the center frequency to be in the allowable range
center_freq_hz = constrain_float(center_freq_hz, 1.0f, _sample_freq_hz * 0.48f);
// update all of the filters using the new center frequency and existing A & Q
for (uint8_t i = 0, filt = 0; i < HNF_MAX_HARMONICS && filt < _num_filters; i++) {
if ((1U<<i) & _harmonics) {
_filters[filt++].init_with_A_and_Q(_sample_freq_hz, center_freq_hz * (i+1), _A, _Q);
@ -138,6 +147,9 @@ void HarmonicNotchFilter<T>::update(float center_freq_hz)
}
}
/*
apply a sample to each of the underlying filters in turn and return the output
*/
template <class T>
T HarmonicNotchFilter<T>::apply(const T &sample)
{
@ -152,6 +164,9 @@ T HarmonicNotchFilter<T>::apply(const T &sample)
return output;
}
/*
reset all of the underlying filters
*/
template <class T>
void HarmonicNotchFilter<T>::reset()
{
@ -164,9 +179,8 @@ void HarmonicNotchFilter<T>::reset()
}
}
/*
a notch filter with enable and filter parameters - constructor
create parameters for the harmonic notch filter and initialise defaults
*/
HarmonicNotchFilterParams::HarmonicNotchFilterParams(void)
{
@ -174,6 +188,6 @@ HarmonicNotchFilterParams::HarmonicNotchFilterParams(void)
}
/*
instantiate template classes
instantiate template classes
*/
template class HarmonicNotchFilter<Vector3f>;

View File

@ -16,44 +16,62 @@
#include <AP_Math/AP_Math.h>
#include <cmath>
#include <inttypes.h>
#include <AP_Param/AP_Param.h>
#include "NotchFilter.h"
/*
a filter that manages a set of notch filters targetted at a fundamental center frequency
and multiples of that fundamental frequency
*/
template <class T>
class HarmonicNotchFilter {
public:
// set parameters
void create(uint8_t harmonics);
void init(float sample_freq_hz, float center_freq_hz, float bandwidth_hz, float attenuation_dB);
T apply(const T &sample);
void reset();
void update(float center_freq_hz);
~HarmonicNotchFilter();
// allocate a bank of notch filters for this harmonic notch filter
void allocate_filters(uint8_t harmonics);
// initialize the underlying filters using the provided filter parameters
void init(float sample_freq_hz, float center_freq_hz, float bandwidth_hz, float attenuation_dB);
// update the underlying filters' center frequencies using center_freq_hz as the fundamental
void update(float center_freq_hz);
// apply a sample to each of the underlying filters in turn
T apply(const T &sample);
// reset each of the underlying filters
void reset();
private:
// underlying bank of notch filters
NotchFilter<T>* _filters;
// sample frequency for each filter
float _sample_freq_hz;
// attenuation for each filter
float _A;
// quality factor of each filter
float _Q;
// a bitmask of the harmonics to use
uint8_t _harmonics;
// number of allocated filters
uint8_t _num_filters;
bool _initialised;
};
/*
notch filter enable and filter parameters
harmonic notch filter configuration parameters
*/
class HarmonicNotchFilterParams : public NotchFilterParams {
public:
HarmonicNotchFilterParams(void);
// set the fundamental center frequency of the harmonic notch
void set_center_freq_hz(float center_freq) { _center_freq_hz.set(center_freq); }
// harmonics enabled on the harmonic notch
uint8_t harmonics(void) const { return _harmonics; }
// reference value of the harmonic notch
float reference(void) const { return _reference; }
static const struct AP_Param::GroupInfo var_info[];
private:
// notch harmonics
AP_Int8 _harmonics;
// notch reference value
AP_Float _reference;
};