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Redesign acceleration and magnetic rejection features #116

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Aug 3, 2023
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Redesign acceleration and magnetic rejection features #116

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2 changes: 1 addition & 1 deletion Examples/Advanced/main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,7 @@ int main() {
.gain = 0.5f,
.accelerationRejection = 10.0f,
.magneticRejection = 20.0f,
.rejectionTimeout = 5 * SAMPLE_RATE, /* 5 seconds */
.recoveryTriggerPeriod = 5 * SAMPLE_RATE, /* 5 seconds */
};
FusionAhrsSetSettings(&ahrs, &settings);

Expand Down
125 changes: 75 additions & 50 deletions Fusion/FusionAhrs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,6 @@

#include <float.h> // FLT_MAX
#include "FusionAhrs.h"
#include "FusionCompass.h"
#include <math.h> // atan2f, cosf, powf, sinf

//------------------------------------------------------------------------------
Expand All @@ -29,11 +28,13 @@
//------------------------------------------------------------------------------
// Function declarations

static FusionVector HalfGravity(const FusionAhrs *const ahrs);
static inline FusionVector HalfGravity(const FusionAhrs *const ahrs);

static FusionVector HalfMagnetic(const FusionAhrs *const ahrs);
static inline FusionVector HalfMagnetic(const FusionAhrs *const ahrs);

static FusionVector Feedback(const FusionVector sensor, const FusionVector reference);
static inline FusionVector Feedback(const FusionVector sensor, const FusionVector reference);

static inline int Clamp(const int value, const int min, const int max);

//------------------------------------------------------------------------------
// Functions
Expand All @@ -48,7 +49,7 @@ void FusionAhrsInitialise(FusionAhrs *const ahrs) {
.gain = 0.5f,
.accelerationRejection = 90.0f,
.magneticRejection = 90.0f,
.rejectionTimeout = 0,
.recoveryTriggerPeriod = 0,
};
FusionAhrsSetSettings(ahrs, &settings);
FusionAhrsReset(ahrs);
Expand All @@ -67,11 +68,11 @@ void FusionAhrsReset(FusionAhrs *const ahrs) {
ahrs->halfAccelerometerFeedback = FUSION_VECTOR_ZERO;
ahrs->halfMagnetometerFeedback = FUSION_VECTOR_ZERO;
ahrs->accelerometerIgnored = false;
ahrs->accelerationRejectionTimer = 0;
ahrs->accelerationRejectionTimeout = false;
ahrs->accelerationRecoveryTrigger = 0;
ahrs->accelerationRecoveryTimeout = ahrs->settings.recoveryTriggerPeriod;
ahrs->magnetometerIgnored = false;
ahrs->magneticRejectionTimer = 0;
ahrs->magneticRejectionTimeout = false;
ahrs->magneticRecoveryTrigger = 0;
ahrs->magneticRecoveryTimeout = ahrs->settings.recoveryTriggerPeriod;
}

/**
Expand All @@ -84,8 +85,10 @@ void FusionAhrsSetSettings(FusionAhrs *const ahrs, const FusionAhrsSettings *con
ahrs->settings.gain = settings->gain;
ahrs->settings.accelerationRejection = settings->accelerationRejection == 0.0f ? FLT_MAX : powf(0.5f * sinf(FusionDegreesToRadians(settings->accelerationRejection)), 2);
ahrs->settings.magneticRejection = settings->magneticRejection == 0.0f ? FLT_MAX : powf(0.5f * sinf(FusionDegreesToRadians(settings->magneticRejection)), 2);
ahrs->settings.rejectionTimeout = settings->rejectionTimeout;
if ((settings->gain == 0.0f) || (settings->rejectionTimeout == 0)) {
ahrs->settings.recoveryTriggerPeriod = settings->recoveryTriggerPeriod;
ahrs->accelerationRecoveryTimeout = ahrs->settings.recoveryTriggerPeriod;
ahrs->magneticRecoveryTimeout = ahrs->settings.recoveryTriggerPeriod;
if ((settings->gain == 0.0f) || (settings->recoveryTriggerPeriod == 0)) {
ahrs->settings.accelerationRejection = FLT_MAX;
ahrs->settings.magneticRejection = FLT_MAX;
}
Expand Down Expand Up @@ -116,7 +119,6 @@ void FusionAhrsUpdate(FusionAhrs *const ahrs, const FusionVector gyroscope, cons
if ((ahrs->rampedGain < ahrs->settings.gain) || (ahrs->settings.gain == 0.0f)) {
ahrs->rampedGain = ahrs->settings.gain;
ahrs->initialising = false;
ahrs->accelerationRejectionTimeout = false;
}
}

Expand All @@ -128,25 +130,29 @@ void FusionAhrsUpdate(FusionAhrs *const ahrs, const FusionVector gyroscope, cons
ahrs->accelerometerIgnored = true;
if (FusionVectorIsZero(accelerometer) == false) {

// Enter acceleration recovery state if acceleration rejection times out
if (ahrs->accelerationRejectionTimer > ahrs->settings.rejectionTimeout) {
const FusionQuaternion quaternion = ahrs->quaternion;
FusionAhrsReset(ahrs);
ahrs->quaternion = quaternion;
ahrs->accelerationRejectionTimer = 0;
ahrs->accelerationRejectionTimeout = true;
}

// Calculate accelerometer feedback scaled by 0.5
ahrs->halfAccelerometerFeedback = Feedback(FusionVectorNormalise(accelerometer), halfGravity);

// Ignore accelerometer if acceleration distortion detected
if ((ahrs->initialising == true) || (FusionVectorMagnitudeSquared(ahrs->halfAccelerometerFeedback) <= ahrs->settings.accelerationRejection)) {
halfAccelerometerFeedback = ahrs->halfAccelerometerFeedback;
// Don't ignore accelerometer if acceleration error below threshold
if ((ahrs->initialising == true) || ((FusionVectorMagnitudeSquared(ahrs->halfAccelerometerFeedback) <= ahrs->settings.accelerationRejection))) {
ahrs->accelerometerIgnored = false;
ahrs->accelerationRecoveryTrigger -= 9;
} else {
ahrs->accelerationRecoveryTrigger += 1;
}

// Don't ignore accelerometer during acceleration recovery
if (ahrs->accelerationRecoveryTrigger > ahrs->accelerationRecoveryTimeout) {
ahrs->accelerationRecoveryTimeout = 0;
ahrs->accelerometerIgnored = false;
ahrs->accelerationRejectionTimer -= ahrs->accelerationRejectionTimer >= 10 ? 10 : 0;
} else {
ahrs->accelerationRejectionTimer++;
ahrs->accelerationRecoveryTimeout = ahrs->settings.recoveryTriggerPeriod;
}
ahrs->accelerationRecoveryTrigger = Clamp(ahrs->accelerationRecoveryTrigger, 0, ahrs->settings.recoveryTriggerPeriod);

// Apply accelerometer feedback
if (ahrs->accelerometerIgnored == false) {
halfAccelerometerFeedback = ahrs->halfAccelerometerFeedback;
}
}

Expand All @@ -155,27 +161,32 @@ void FusionAhrsUpdate(FusionAhrs *const ahrs, const FusionVector gyroscope, cons
ahrs->magnetometerIgnored = true;
if (FusionVectorIsZero(magnetometer) == false) {

// Set to compass heading if magnetic rejection times out
ahrs->magneticRejectionTimeout = false;
if (ahrs->magneticRejectionTimer > ahrs->settings.rejectionTimeout) {
FusionAhrsSetHeading(ahrs, FusionCompassCalculateHeading(ahrs->settings.convention, halfGravity, magnetometer));
ahrs->magneticRejectionTimer = 0;
ahrs->magneticRejectionTimeout = true;
}

// Calculate direction of magnetic field indicated by algorithm
const FusionVector halfMagnetic = HalfMagnetic(ahrs);

// Calculate magnetometer feedback scaled by 0.5
ahrs->halfMagnetometerFeedback = Feedback(FusionVectorNormalise(FusionVectorCrossProduct(halfGravity, magnetometer)), halfMagnetic);

// Ignore magnetometer if magnetic distortion detected
if ((ahrs->initialising == true) || (FusionVectorMagnitudeSquared(ahrs->halfMagnetometerFeedback) <= ahrs->settings.magneticRejection)) {
halfMagnetometerFeedback = ahrs->halfMagnetometerFeedback;
// Don't ignore magnetometer if magnetic error below threshold
if ((ahrs->initialising == true) || ((FusionVectorMagnitudeSquared(ahrs->halfMagnetometerFeedback) <= ahrs->settings.magneticRejection))) {
ahrs->magnetometerIgnored = false;
ahrs->magneticRejectionTimer -= ahrs->magneticRejectionTimer >= 10 ? 10 : 0;
ahrs->magneticRecoveryTrigger -= 9;
} else {
ahrs->magneticRejectionTimer++;
ahrs->magneticRecoveryTrigger += 1;
}

// Don't ignore magnetometer during magnetic recovery
if (ahrs->magneticRecoveryTrigger > ahrs->magneticRecoveryTimeout) {
ahrs->magneticRecoveryTimeout = 0;
ahrs->magnetometerIgnored = false;
} else {
ahrs->magneticRecoveryTimeout = ahrs->settings.recoveryTriggerPeriod;
}
ahrs->magneticRecoveryTrigger = Clamp(ahrs->magneticRecoveryTrigger, 0, ahrs->settings.recoveryTriggerPeriod);

// Apply magnetometer feedback
if (ahrs->magnetometerIgnored == false) {
halfMagnetometerFeedback = ahrs->halfMagnetometerFeedback;
}
}

Expand All @@ -198,7 +209,7 @@ void FusionAhrsUpdate(FusionAhrs *const ahrs, const FusionVector gyroscope, cons
* @param ahrs AHRS algorithm structure.
* @return Direction of gravity scaled by 0.5.
*/
static FusionVector HalfGravity(const FusionAhrs *const ahrs) {
static inline FusionVector HalfGravity(const FusionAhrs *const ahrs) {
#define Q ahrs->quaternion.element
switch (ahrs->settings.convention) {
case FusionConventionNwu:
Expand Down Expand Up @@ -228,7 +239,7 @@ static FusionVector HalfGravity(const FusionAhrs *const ahrs) {
* @param ahrs AHRS algorithm structure.
* @return Direction of the magnetic field scaled by 0.5.
*/
static FusionVector HalfMagnetic(const FusionAhrs *const ahrs) {
static inline FusionVector HalfMagnetic(const FusionAhrs *const ahrs) {
#define Q ahrs->quaternion.element
switch (ahrs->settings.convention) {
case FusionConventionNwu: {
Expand Down Expand Up @@ -266,13 +277,30 @@ static FusionVector HalfMagnetic(const FusionAhrs *const ahrs) {
* @param reference Reference.
* @return Feedback.
*/
static FusionVector Feedback(const FusionVector sensor, const FusionVector reference) {
static inline FusionVector Feedback(const FusionVector sensor, const FusionVector reference) {
if (FusionVectorDotProduct(sensor, reference) < 0.0f) { // if error is >90 degrees
return FusionVectorNormalise(FusionVectorCrossProduct(sensor, reference));
}
return FusionVectorCrossProduct(sensor, reference);
}

/**
* @brief Returns a value limited to maximum and minimum.
* @param value Value.
* @param min Minimum value.
* @param max Maximum value.
* @return Value limited to maximum and minimum.
*/
static inline int Clamp(const int value, const int min, const int max) {
if (value < min) {
return min;
}
if (value > max) {
return max;
}
return value;
}

/**
* @brief Updates the AHRS algorithm using the gyroscope and accelerometer
* measurements only.
Expand All @@ -287,7 +315,7 @@ void FusionAhrsUpdateNoMagnetometer(FusionAhrs *const ahrs, const FusionVector g
FusionAhrsUpdate(ahrs, gyroscope, accelerometer, FUSION_VECTOR_ZERO, deltaTime);

// Zero heading during initialisation
if ((ahrs->initialising == true) && (ahrs->accelerationRejectionTimeout == false)) {
if (ahrs->initialising == true) {
FusionAhrsSetHeading(ahrs, 0.0f);
}
}
Expand Down Expand Up @@ -417,10 +445,10 @@ FusionAhrsInternalStates FusionAhrsGetInternalStates(const FusionAhrs *const ahr
const FusionAhrsInternalStates internalStates = {
.accelerationError = FusionRadiansToDegrees(FusionAsin(2.0f * FusionVectorMagnitude(ahrs->halfAccelerometerFeedback))),
.accelerometerIgnored = ahrs->accelerometerIgnored,
.accelerationRejectionTimer = ahrs->settings.rejectionTimeout == 0 ? 0.0f : (float) ahrs->accelerationRejectionTimer / (float) ahrs->settings.rejectionTimeout,
.accelerationRecoveryTrigger = ahrs->settings.recoveryTriggerPeriod == 0 ? 0.0f : (float) ahrs->accelerationRecoveryTrigger / (float) ahrs->settings.recoveryTriggerPeriod,
.magneticError = FusionRadiansToDegrees(FusionAsin(2.0f * FusionVectorMagnitude(ahrs->halfMagnetometerFeedback))),
.magnetometerIgnored = ahrs->magnetometerIgnored,
.magneticRejectionTimer = ahrs->settings.rejectionTimeout == 0 ? 0.0f : (float) ahrs->magneticRejectionTimer / (float) ahrs->settings.rejectionTimeout,
.magneticRecoveryTrigger = ahrs->settings.recoveryTriggerPeriod == 0 ? 0.0f : (float) ahrs->magneticRecoveryTrigger / (float) ahrs->settings.recoveryTriggerPeriod,
};
return internalStates;
}
Expand All @@ -431,13 +459,10 @@ FusionAhrsInternalStates FusionAhrsGetInternalStates(const FusionAhrs *const ahr
* @return AHRS algorithm flags.
*/
FusionAhrsFlags FusionAhrsGetFlags(const FusionAhrs *const ahrs) {
const unsigned int warningTimeout = ahrs->settings.rejectionTimeout / 4;
const FusionAhrsFlags flags = {
.initialising = ahrs->initialising,
.accelerationRejectionWarning = ahrs->accelerationRejectionTimer > warningTimeout,
.accelerationRejectionTimeout = ahrs->accelerationRejectionTimeout,
.magneticRejectionWarning = ahrs->magneticRejectionTimer > warningTimeout,
.magneticRejectionTimeout = ahrs->magneticRejectionTimeout,
.accelerationRecovery = ahrs->accelerationRecoveryTrigger > ahrs->accelerationRecoveryTimeout,
.magneticRecovery= ahrs->magneticRecoveryTrigger > ahrs->magneticRecoveryTimeout,
};
return flags;
}
Expand Down
20 changes: 9 additions & 11 deletions Fusion/FusionAhrs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ typedef struct {
float gain;
float accelerationRejection;
float magneticRejection;
unsigned int rejectionTimeout;
unsigned int recoveryTriggerPeriod;
} FusionAhrsSettings;

/**
Expand All @@ -43,11 +43,11 @@ typedef struct {
FusionVector halfAccelerometerFeedback;
FusionVector halfMagnetometerFeedback;
bool accelerometerIgnored;
unsigned int accelerationRejectionTimer;
bool accelerationRejectionTimeout;
int accelerationRecoveryTrigger;
int accelerationRecoveryTimeout;
bool magnetometerIgnored;
unsigned int magneticRejectionTimer;
bool magneticRejectionTimeout;
int magneticRecoveryTrigger;
int magneticRecoveryTimeout;
} FusionAhrs;

/**
Expand All @@ -56,21 +56,19 @@ typedef struct {
typedef struct {
float accelerationError;
bool accelerometerIgnored;
float accelerationRejectionTimer;
float accelerationRecoveryTrigger;
float magneticError;
bool magnetometerIgnored;
float magneticRejectionTimer;
float magneticRecoveryTrigger;
} FusionAhrsInternalStates;

/**
* @brief AHRS algorithm flags.
*/
typedef struct {
bool initialising;
bool accelerationRejectionWarning;
bool accelerationRejectionTimeout;
bool magneticRejectionWarning;
bool magneticRejectionTimeout;
bool accelerationRecovery;
bool magneticRecovery;
} FusionAhrsFlags;

//------------------------------------------------------------------------------
Expand Down
24 changes: 7 additions & 17 deletions Python/Python-C-API/Flags.h
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Original file line number Diff line number Diff line change
Expand Up @@ -18,28 +18,18 @@ static PyObject *flags_get_initialising(Flags *self) {
return build_bool(self->flags.initialising);
}

static PyObject *flags_get_acceleration_rejection_warning(Flags *self) {
return build_bool(self->flags.accelerationRejectionWarning);
static PyObject *flags_get_acceleration_recovery(Flags *self) {
return build_bool(self->flags.accelerationRecovery);
}

static PyObject *flags_get_acceleration_rejection_timeout(Flags *self) {
return build_bool(self->flags.accelerationRejectionTimeout);
}

static PyObject *flags_get_magnetic_rejection_warning(Flags *self) {
return build_bool(self->flags.magneticRejectionWarning);
}

static PyObject *flags_get_magnetic_rejection_timeout(Flags *self) {
return build_bool(self->flags.magneticRejectionTimeout);
static PyObject *flags_get_magnetic_recovery(Flags *self) {
return build_bool(self->flags.magneticRecovery);
}

static PyGetSetDef flags_get_set[] = {
{"initialising", (getter) flags_get_initialising, NULL, "", NULL},
{"acceleration_rejection_warning", (getter) flags_get_acceleration_rejection_warning, NULL, "", NULL},
{"acceleration_rejection_timeout", (getter) flags_get_acceleration_rejection_timeout, NULL, "", NULL},
{"magnetic_rejection_warning", (getter) flags_get_magnetic_rejection_warning, NULL, "", NULL},
{"magnetic_rejection_timeout", (getter) flags_get_magnetic_rejection_timeout, NULL, "", NULL},
{"initialising", (getter) flags_get_initialising, NULL, "", NULL},
{"acceleration_recovery", (getter) flags_get_acceleration_recovery, NULL, "", NULL},
{"magnetic_recovery", (getter) flags_get_magnetic_recovery, NULL, "", NULL},
{NULL} /* sentinel */
};

Expand Down
20 changes: 10 additions & 10 deletions Python/Python-C-API/InternalStates.h
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Expand Up @@ -22,8 +22,8 @@ static PyObject *internal_states_get_accelerometer_ignored(InternalStates *self)
return build_bool(self->internal_states.accelerometerIgnored);
}

static PyObject *internal_states_get_acceleration_rejection_timer(InternalStates *self) {
return Py_BuildValue("f", self->internal_states.accelerationRejectionTimer);
static PyObject *internal_states_get_acceleration_recovery_trigger(InternalStates *self) {
return Py_BuildValue("f", self->internal_states.accelerationRecoveryTrigger);
}

static PyObject *internal_states_get_magnetic_error(InternalStates *self) {
Expand All @@ -34,17 +34,17 @@ static PyObject *internal_states_get_magnetometer_ignored(InternalStates *self)
return build_bool(self->internal_states.magnetometerIgnored);
}

static PyObject *internal_states_get_magnetic_rejection_timer(InternalStates *self) {
return Py_BuildValue("f", self->internal_states.magneticRejectionTimer);
static PyObject *internal_states_get_magnetic_recovery_trigger(InternalStates *self) {
return Py_BuildValue("f", self->internal_states.magneticRecoveryTrigger);
}

static PyGetSetDef internal_states_get_set[] = {
{"acceleration_error", (getter) internal_states_get_acceleration_error, NULL, "", NULL},
{"accelerometer_ignored", (getter) internal_states_get_accelerometer_ignored, NULL, "", NULL},
{"acceleration_rejection_timer", (getter) internal_states_get_acceleration_rejection_timer, NULL, "", NULL},
{"magnetic_error", (getter) internal_states_get_magnetic_error, NULL, "", NULL},
{"magnetometer_ignored", (getter) internal_states_get_magnetometer_ignored, NULL, "", NULL},
{"magnetic_rejection_timer", (getter) internal_states_get_magnetic_rejection_timer, NULL, "", NULL},
{"acceleration_error", (getter) internal_states_get_acceleration_error, NULL, "", NULL},
{"accelerometer_ignored", (getter) internal_states_get_accelerometer_ignored, NULL, "", NULL},
{"acceleration_recovery_trigger", (getter) internal_states_get_acceleration_recovery_trigger, NULL, "", NULL},
{"magnetic_error", (getter) internal_states_get_magnetic_error, NULL, "", NULL},
{"magnetometer_ignored", (getter) internal_states_get_magnetometer_ignored, NULL, "", NULL},
{"magnetic_recovery_trigger", (getter) internal_states_get_magnetic_recovery_trigger, NULL, "", NULL},
{NULL} /* sentinel */
};

Expand Down
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