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Dynamic filter performance improvement for 16k and 32k gyro loop frequency (#5450)

* * FAST_RAM-ing variables used to compute FFT
* Eradicated global static variables in favour of define
* FFT_WINDOW_SIZE / 2 replaced with FFT_BIN_COUNT
* Limit call count of filters update to necessary minimum on 32k and 16k gyro sampling rate
* Dynamic filter recalculation freq. is at least FFT_SAMPLING_RATE + update time
* Moved global variables used in local scope only to local scope

* * Based on diehertzs review I removed all 0 initializations of global variables

* * Fixed calculation of update frequency for center frequency filter, thx rav-rav for pointing the problem

* * Silenced the warning signed vs unsigned comparison

* * Replaced magick values 3*4 and 12 with preprocessor macro as requested by DieHertz

* * Replaced hardcoded axis count with proper preprocessor macro
This commit is contained in:
Miroslav Drbal [ApoC] 2018-03-20 12:17:34 +01:00 committed by Michael Keller
parent c182748dbb
commit 3ce8223c96
2 changed files with 49 additions and 46 deletions

View file

@ -39,43 +39,42 @@
// A sampling frequency of 1000 and max frequency of 500 at a window size of 32 gives 16 frequency bins each with a width 31.25Hz
// Eg [0,31), [31,62), [62, 93) etc
#define FFT_WINDOW_SIZE 32 // max for f3 targets
#define FFT_MIN_FREQ 100 // not interested in filtering frequencies below 100Hz
#define FFT_SAMPLING_RATE 1000 // allows analysis up to 500Hz which is more than motors create
#define FFT_BPF_HZ 200 // use a bandpass on gyro data to ignore extreme low and extreme high frequencies
#define DYN_NOTCH_WIDTH 100 // just an orientation and start value
#define DYN_NOTCH_CHANGERATE 60 // lower cut does not improve the performance much, higher cut makes it worse...
#define DYN_NOTCH_MIN_CUTOFF 120 // don't cut too deep into low frequencies
#define DYN_NOTCH_MAX_CUTOFF 200 // don't go above this cutoff (better filtering with "constant" delay at higher center frequencies)
#define FFT_WINDOW_SIZE 32 // max for f3 targets
#define FFT_BIN_COUNT (FFT_WINDOW_SIZE / 2)
#define FFT_MIN_FREQ 100 // not interested in filtering frequencies below 100Hz
#define FFT_SAMPLING_RATE 1000 // allows analysis up to 500Hz which is more than motors create
#define FFT_MAX_FREQUENCY (FFT_SAMPLING_RATE / 2) // nyquist rate
#define FFT_BPF_HZ 200 // use a bandpass on gyro data to ignore extreme low and extreme high frequencies
#define FFT_RESOLUTION ((float)FFT_SAMPLING_RATE / FFT_WINDOW_SIZE) // hz per bin
#define DYN_NOTCH_WIDTH 100 // just an orientation and start value
#define DYN_NOTCH_CHANGERATE 60 // lower cut does not improve the performance much, higher cut makes it worse...
#define DYN_NOTCH_MIN_CUTOFF 120 // don't cut too deep into low frequencies
#define DYN_NOTCH_MAX_CUTOFF 200 // don't go above this cutoff (better filtering with "constant" delay at higher center frequencies)
#define DYN_NOTCH_CALC_TICKS (XYZ_AXIS_COUNT * 4) // we need 4 steps for each axis
#define BIQUAD_Q 1.0f / sqrtf(2.0f) // quality factor - butterworth
static uint16_t samplingFrequency; // gyro rate
static uint8_t fftBinCount;
static float fftResolution; // hz per bin
static float gyroData[3][FFT_WINDOW_SIZE]; // gyro data used for frequency analysis
static FAST_RAM uint16_t fftSamplingScale;
static arm_rfft_fast_instance_f32 fftInstance;
static float fftData[FFT_WINDOW_SIZE];
static float rfftData[FFT_WINDOW_SIZE];
static gyroFftData_t fftResult[3];
static uint16_t fftMaxFreq = 0; // nyquist rate
static uint16_t fftIdx = 0; // use a circular buffer for the last FFT_WINDOW_SIZE samples
// gyro data used for frequency analysis
static float FAST_RAM gyroData[XYZ_AXIS_COUNT][FFT_WINDOW_SIZE];
static FAST_RAM arm_rfft_fast_instance_f32 fftInstance;
static FAST_RAM float fftData[FFT_WINDOW_SIZE];
static FAST_RAM float rfftData[FFT_WINDOW_SIZE];
static FAST_RAM gyroFftData_t fftResult[XYZ_AXIS_COUNT];
// accumulator for oversampled data => no aliasing and less noise
static float fftAcc[3] = {0, 0, 0};
static int fftAccCount = 0;
static int fftSamplingScale;
// use a circular buffer for the last FFT_WINDOW_SIZE samples
static FAST_RAM uint16_t fftIdx;
// bandpass filter gyro data
static biquadFilter_t fftGyroFilter[3];
static FAST_RAM biquadFilter_t fftGyroFilter[XYZ_AXIS_COUNT];
// filter for smoothing frequency estimation
static biquadFilter_t fftFreqFilter[3];
static FAST_RAM biquadFilter_t fftFreqFilter[XYZ_AXIS_COUNT];
// Hanning window, see https://en.wikipedia.org/wiki/Window_function#Hann_.28Hanning.29_window
static float hanningWindow[FFT_WINDOW_SIZE];
static FAST_RAM float hanningWindow[FFT_WINDOW_SIZE];
void initHanning(void)
{
@ -93,27 +92,20 @@ void initGyroData(void)
}
}
static inline int fftFreqToBin(int freq)
{
return ((FFT_WINDOW_SIZE / 2 - 1) * freq) / (fftMaxFreq);
}
void gyroDataAnalyseInit(uint32_t targetLooptimeUs)
{
// initialise even if FEATURE_DYNAMIC_FILTER not set, since it may be set later
samplingFrequency = 1000000 / targetLooptimeUs;
const uint16_t samplingFrequency = 1000000 / targetLooptimeUs;
fftSamplingScale = samplingFrequency / FFT_SAMPLING_RATE;
fftMaxFreq = FFT_SAMPLING_RATE / 2;
fftBinCount = fftFreqToBin(fftMaxFreq) + 1;
fftResolution = FFT_SAMPLING_RATE / FFT_WINDOW_SIZE;
arm_rfft_fast_init_f32(&fftInstance, FFT_WINDOW_SIZE);
initGyroData();
initHanning();
// recalculation of filters takes 4 calls per axis => each filter gets updated every 3 * 4 = 12 calls
// recalculation of filters takes 4 calls per axis => each filter gets updated every DYN_NOTCH_CALC_TICKS calls
// at 4khz gyro loop rate this means 4khz / 4 / 3 = 333Hz => update every 3ms
float looptime = targetLooptimeUs * 4 * 3;
// for gyro rate > 16kHz, we have update frequency of 1kHz => 1ms
const float looptime = MAX(1000000u / FFT_SAMPLING_RATE, targetLooptimeUs * DYN_NOTCH_CALC_TICKS);
for (int axis = 0; axis < XYZ_AXIS_COUNT; axis++) {
fftResult[axis].centerFreq = 200; // any init value
biquadFilterInitLPF(&fftFreqFilter[axis], DYN_NOTCH_CHANGERATE, looptime);
@ -132,6 +124,12 @@ const gyroFftData_t *gyroFftData(int axis)
*/
void gyroDataAnalyse(const gyroDev_t *gyroDev, biquadFilter_t *notchFilterDyn)
{
// accumulator for oversampled data => no aliasing and less noise
static FAST_RAM float fftAcc[XYZ_AXIS_COUNT];
static FAST_RAM uint32_t fftAccCount;
static FAST_RAM uint32_t gyroDataAnalyseUpdateTicks;
// if gyro sampling is > 1kHz, accumulate multiple samples
for (int axis = 0; axis < XYZ_AXIS_COUNT; axis++) {
fftAcc[axis] += gyroDev->gyroADC[axis];
@ -153,10 +151,16 @@ void gyroDataAnalyse(const gyroDev_t *gyroDev, biquadFilter_t *notchFilterDyn)
}
fftIdx = (fftIdx + 1) % FFT_WINDOW_SIZE;
// We need DYN_NOTCH_CALC_TICKS tick to update all axis with newly sampled value
gyroDataAnalyseUpdateTicks = DYN_NOTCH_CALC_TICKS;
}
// calculate FFT and update filters
gyroDataAnalyseUpdate(notchFilterDyn);
if (gyroDataAnalyseUpdateTicks > 0) {
gyroDataAnalyseUpdate(notchFilterDyn);
--gyroDataAnalyseUpdateTicks;
}
}
void stage_rfft_f32(arm_rfft_fast_instance_f32 * S, float32_t * p, float32_t * pOut);
@ -181,8 +185,8 @@ typedef enum {
*/
void gyroDataAnalyseUpdate(biquadFilter_t *notchFilterDyn)
{
static int axis = 0;
static int step = 0;
static int axis;
static int step;
arm_cfft_instance_f32 * Sint = &(fftInstance.Sint);
uint32_t startTime = 0;
@ -193,7 +197,7 @@ void gyroDataAnalyseUpdate(biquadFilter_t *notchFilterDyn)
switch (step) {
case STEP_ARM_CFFT_F32:
{
switch (FFT_WINDOW_SIZE / 2) {
switch (FFT_BIN_COUNT) {
case 16:
// 16us
arm_cfft_radix8by2_f32(Sint, fftData);
@ -204,7 +208,7 @@ void gyroDataAnalyseUpdate(biquadFilter_t *notchFilterDyn)
break;
case 64:
// 70us
arm_radix8_butterfly_f32(fftData, FFT_WINDOW_SIZE / 2, Sint->pTwiddle, 1);
arm_radix8_butterfly_f32(fftData, FFT_BIN_COUNT, Sint->pTwiddle, 1);
break;
}
DEBUG_SET(DEBUG_FFT_TIME, 1, micros() - startTime);
@ -229,7 +233,7 @@ void gyroDataAnalyseUpdate(biquadFilter_t *notchFilterDyn)
case STEP_ARM_CMPLX_MAG_F32:
{
// 8us
arm_cmplx_mag_f32(rfftData, fftData, fftBinCount);
arm_cmplx_mag_f32(rfftData, fftData, FFT_BIN_COUNT);
DEBUG_SET(DEBUG_FFT_TIME, 2, micros() - startTime);
step++;
FALLTHROUGH;
@ -243,7 +247,7 @@ void gyroDataAnalyseUpdate(biquadFilter_t *notchFilterDyn)
fftResult[axis].maxVal = 0;
// iterate over fft data and calculate weighted indexes
float squaredData;
for (int i = 0; i < fftBinCount; i++) {
for (int i = 0; i < FFT_BIN_COUNT; i++) {
squaredData = fftData[i] * fftData[i]; //more weight on higher peaks
fftResult[axis].maxVal = MAX(fftResult[axis].maxVal, squaredData);
fftSum += squaredData;
@ -259,9 +263,9 @@ void gyroDataAnalyseUpdate(biquadFilter_t *notchFilterDyn)
// don't go below the minimal cutoff frequency + 10 and don't jump around too much
float centerFreq;
centerFreq = constrain(fftMeanIndex * fftResolution, DYN_NOTCH_MIN_CUTOFF + 10, fftMaxFreq);
centerFreq = constrain(fftMeanIndex * FFT_RESOLUTION, DYN_NOTCH_MIN_CUTOFF + 10, FFT_MAX_FREQUENCY);
centerFreq = biquadFilterApply(&fftFreqFilter[axis], centerFreq);
centerFreq = constrain(centerFreq, DYN_NOTCH_MIN_CUTOFF + 10, fftMaxFreq);
centerFreq = constrain(centerFreq, DYN_NOTCH_MIN_CUTOFF + 10, FFT_MAX_FREQUENCY);
fftResult[axis].centerFreq = centerFreq;
if (axis == 0) {
DEBUG_SET(DEBUG_FFT, 3, lrintf(fftMeanIndex * 100));

View file

@ -20,7 +20,6 @@
#include "common/time.h"
#include "common/filter.h"
#define GYRO_FFT_BIN_COUNT 16 // FFT_WINDOW_SIZE / 2
typedef struct gyroFftData_s {
float maxVal;
uint16_t centerFreq;