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AP_InertialSensor: more accurately compute INS noise taking throttle into account and adding frequency noise noisily

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make SITL fast-sampling correct
This commit is contained in:
Andy Piper 2019-12-24 21:19:34 +00:00 committed by Andrew Tridgell
parent 8b0fc1207d
commit 52f59fb573
1 changed files with 129 additions and 103 deletions
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232
libraries/AP_InertialSensor/AP_InertialSensor_SITL.cpp
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@ -55,37 +55,60 @@ bool AP_InertialSensor_SITL::init_sensor(void)
return true; return true;
} }
// calculate a noisy noise component
static float calculate_noise(float noise, float noise_variation) {
return noise * (1.0f + noise_variation * rand_float());
}
/* /*
generate an accelerometer sample generate an accelerometer sample
*/ */
void AP_InertialSensor_SITL::generate_accel(uint8_t instance) void AP_InertialSensor_SITL::generate_accel(uint8_t instance)
{ {
// minimum noise levels are 2 bits, but averaged over many Vector3f accel_accum;
// samples, giving around 0.01 m/s/s uint8_t nsamples = enable_fast_sampling(accel_instance[instance]) ? 4 : 1;
float accel_noise = 0.01f; for (uint8_t j = 0; j < nsamples; j++) {
if (sitl->motors_on) { // add accel bias and noise
// add extra noise when the motors are on Vector3f accel_bias = instance == 0 ? sitl->accel_bias.get() : sitl->accel2_bias.get();
accel_noise += instance == 0 ? sitl->accel_noise : sitl->accel2_noise; float xAccel = sitl->state.xAccel + accel_bias.x;
} float yAccel = sitl->state.yAccel + accel_bias.y;
float zAccel = sitl->state.zAccel + accel_bias.z;
// minimum noise levels are 2 bits, but averaged over many
// samples, giving around 0.01 m/s/s
float accel_noise = 0.01f;
float noise_variation = 0.05;
// this smears the individual motor peaks somewhat emulating physical motors
float freq_variation = 0.12;
// add accel bias and noise
Vector3f accel_bias = instance == 0 ? sitl->accel_bias.get() : sitl->accel2_bias.get();
float xAccel = sitl->state.xAccel + accel_bias.x;
float yAccel = sitl->state.yAccel + accel_bias.y;
float zAccel = sitl->state.zAccel + accel_bias.z;
const Vector3f &vibe_freq = sitl->vibe_freq;
bool vibe_motor = !is_zero(sitl->vibe_motor);
if (vibe_freq.is_zero() && !vibe_motor) {
xAccel += accel_noise * rand_float(); xAccel += accel_noise * rand_float();
yAccel += accel_noise * rand_float(); yAccel += accel_noise * rand_float();
zAccel += accel_noise * rand_float(); zAccel += accel_noise * rand_float();
} else {
if (vibe_motor) { bool motors_on = sitl->throttle > sitl->ins_noise_throttle_min;
// on a real 180mm copter gyro noise varies between 0.8-4 m/s/s for throttle 0.2-0.8
// giving a accel noise variation of 5.33 m/s/s over the full throttle range
if (motors_on) {
// add extra noise when the motors are on
accel_noise = (instance == 0 ? sitl->accel_noise : sitl->accel2_noise) * sitl->throttle;
}
// VIB_FREQ is a static vibration applied to each axis
const Vector3f &vibe_freq = sitl->vibe_freq;
if (!vibe_freq.is_zero() && motors_on) {
float t = AP_HAL::micros() * 1.0e-6f;
xAccel += sinf(t * 2 * M_PI * vibe_freq.x) * calculate_noise(accel_noise, noise_variation);
yAccel += sinf(t * 2 * M_PI * vibe_freq.y) * calculate_noise(accel_noise, noise_variation);
zAccel += sinf(t * 2 * M_PI * vibe_freq.z) * calculate_noise(accel_noise, noise_variation);
}
// VIB_MOT_MAX is a rpm-scaled vibration applied to each axis
if (!is_zero(sitl->vibe_motor) && motors_on) {
for (uint8_t i = 0; i < sitl->state.num_motors; i++) { for (uint8_t i = 0; i < sitl->state.num_motors; i++) {
float& phase = accel_motor_phase[instance][i]; float &phase = accel_motor_phase[instance][i];
float motor_freq = sitl->state.rpm[i] / 60.0f; float motor_freq = calculate_noise(sitl->state.rpm[i] / 60.0f, freq_variation);
float phase_incr = motor_freq * 2 * M_PI / accel_sample_hz[instance]; float phase_incr = motor_freq * 2 * M_PI / (accel_sample_hz[instance] * nsamples);
phase += phase_incr; phase += phase_incr;
if (phase_incr > M_PI) { if (phase_incr > M_PI) {
phase -= 2 * M_PI; phase -= 2 * M_PI;
@ -93,53 +116,48 @@ void AP_InertialSensor_SITL::generate_accel(uint8_t instance)
else if (phase_incr < -M_PI) { else if (phase_incr < -M_PI) {
phase += 2 * M_PI; phase += 2 * M_PI;
} }
xAccel += sinf(phase) * accel_noise; xAccel += sinf(phase) * calculate_noise(accel_noise, noise_variation);
yAccel += sinf(phase) * accel_noise; yAccel += sinf(phase) * calculate_noise(accel_noise, noise_variation);
zAccel += sinf(phase) * accel_noise; zAccel += sinf(phase) * calculate_noise(accel_noise, noise_variation);
} }
} }
if (!vibe_freq.is_zero()) {
float t = AP_HAL::micros() * 1.0e-6f; // correct for the acceleration due to the IMU position offset and angular acceleration
xAccel += sinf(t * 2 * M_PI * vibe_freq.x) * accel_noise; // correct for the centripetal acceleration
yAccel += sinf(t * 2 * M_PI * vibe_freq.y) * accel_noise; // only apply corrections to first accelerometer
zAccel += sinf(t * 2 * M_PI * vibe_freq.z) * accel_noise; Vector3f pos_offset = sitl->imu_pos_offset;
if (!pos_offset.is_zero()) {
// calculate sensed acceleration due to lever arm effect
// Note: the % operator has been overloaded to provide a cross product
Vector3f angular_accel = Vector3f(radians(sitl->state.angAccel.x), radians(sitl->state.angAccel.y), radians(sitl->state.angAccel.z));
Vector3f lever_arm_accel = angular_accel % pos_offset;
// calculate sensed acceleration due to centripetal acceleration
Vector3f angular_rate = Vector3f(radians(sitl->state.rollRate), radians(sitl->state.pitchRate), radians(sitl->state.yawRate));
Vector3f centripetal_accel = angular_rate % (angular_rate % pos_offset);
// apply corrections
xAccel += lever_arm_accel.x + centripetal_accel.x;
yAccel += lever_arm_accel.y + centripetal_accel.y;
zAccel += lever_arm_accel.z + centripetal_accel.z;
} }
}
// correct for the acceleration due to the IMU position offset and angular acceleration
// correct for the centripetal acceleration
// only apply corrections to first accelerometer
Vector3f pos_offset = sitl->imu_pos_offset;
if (!pos_offset.is_zero()) {
// calculate sensed acceleration due to lever arm effect
// Note: the % operator has been overloaded to provide a cross product
Vector3f angular_accel = Vector3f(radians(sitl->state.angAccel.x) , radians(sitl->state.angAccel.y) , radians(sitl->state.angAccel.z));
Vector3f lever_arm_accel = angular_accel % pos_offset;
// calculate sensed acceleration due to centripetal acceleration if (fabsf(sitl->accel_fail) > 1.0e-6f) {
Vector3f angular_rate = Vector3f(radians(sitl->state.rollRate), radians(sitl->state.pitchRate), radians(sitl->state.yawRate)); xAccel = sitl->accel_fail;
Vector3f centripetal_accel = angular_rate % (angular_rate % pos_offset); yAccel = sitl->accel_fail;
zAccel = sitl->accel_fail;
}
// apply corrections Vector3f accel = Vector3f(xAccel, yAccel, zAccel);
xAccel += lever_arm_accel.x + centripetal_accel.x;
yAccel += lever_arm_accel.y + centripetal_accel.y; _rotate_and_correct_accel(accel_instance[instance], accel);
zAccel += lever_arm_accel.z + centripetal_accel.z; _notify_new_accel_sensor_rate_sample(instance, accel);
accel_accum += accel;
} }
if (fabsf(sitl->accel_fail) > 1.0e-6f) { accel_accum /= nsamples;
xAccel = sitl->accel_fail; _notify_new_accel_raw_sample(accel_instance[instance], accel_accum);
yAccel = sitl->accel_fail;
zAccel = sitl->accel_fail;
}
Vector3f accel = Vector3f(xAccel, yAccel, zAccel);
_rotate_and_correct_accel(accel_instance[instance], accel);
uint8_t nsamples = enable_fast_sampling(accel_instance[instance]) ? 4 : 1;
for (uint8_t i=0; i<nsamples; i++) {
_notify_new_accel_raw_sample(accel_instance[instance], accel);
}
_publish_temperature(instance, 23); _publish_temperature(instance, 23);
} }
@ -149,30 +167,46 @@ void AP_InertialSensor_SITL::generate_accel(uint8_t instance)
*/ */
void AP_InertialSensor_SITL::generate_gyro(uint8_t instance) void AP_InertialSensor_SITL::generate_gyro(uint8_t instance)
{ {
// minimum gyro noise is less than 1 bit Vector3f gyro_accum;
float gyro_noise = ToRad(0.04f); uint8_t nsamples = enable_fast_sampling(gyro_instance[instance]) ? 8 : 1;
for (uint8_t j = 0; j < nsamples; j++) {
if (sitl->motors_on) { float p = radians(sitl->state.rollRate) + gyro_drift();
// add extra noise when the motors are on float q = radians(sitl->state.pitchRate) + gyro_drift();
gyro_noise += ToRad(sitl->gyro_noise); float r = radians(sitl->state.yawRate) + gyro_drift();
}
float p = radians(sitl->state.rollRate) + gyro_drift(); // minimum gyro noise is less than 1 bit
float q = radians(sitl->state.pitchRate) + gyro_drift(); float gyro_noise = ToRad(0.04f);
float r = radians(sitl->state.yawRate) + gyro_drift(); float noise_variation = 0.05f;
// this smears the individual motor peaks somewhat emulating physical motors
float freq_variation = 0.12f;
const Vector3f &vibe_freq = sitl->vibe_freq;
bool vibe_motor = !is_zero(sitl->vibe_motor);
if (vibe_freq.is_zero() && !vibe_motor) {
p += gyro_noise * rand_float(); p += gyro_noise * rand_float();
q += gyro_noise * rand_float(); q += gyro_noise * rand_float();
r += gyro_noise * rand_float(); r += gyro_noise * rand_float();
} else {
if (vibe_motor) { bool motors_on = sitl->throttle > sitl->ins_noise_throttle_min;
// on a real 180mm copter gyro noise varies between 0.2-0.4 rad/s for throttle 0.2-0.8
// giving a gyro noise variation of 0.33 rad/s or 20deg/s over the full throttle range
if (motors_on) {
// add extra noise when the motors are on
gyro_noise = ToRad(sitl->gyro_noise) * sitl->throttle;
}
// VIB_FREQ is a static vibration applied to each axis
const Vector3f &vibe_freq = sitl->vibe_freq;
if (!vibe_freq.is_zero() && motors_on) {
float t = AP_HAL::micros() * 1.0e-6f;
p += sinf(t * 2 * M_PI * vibe_freq.x) * calculate_noise(gyro_noise, noise_variation);
q += sinf(t * 2 * M_PI * vibe_freq.y) * calculate_noise(gyro_noise, noise_variation);
r += sinf(t * 2 * M_PI * vibe_freq.z) * calculate_noise(gyro_noise, noise_variation);
}
// VIB_MOT_MAX is a rpm-scaled vibration applied to each axis
if (!is_zero(sitl->vibe_motor) && motors_on) {
for (uint8_t i = 0; i < sitl->state.num_motors; i++) { for (uint8_t i = 0; i < sitl->state.num_motors; i++) {
float motor_freq = sitl->state.rpm[i] / 60.0f; float motor_freq = calculate_noise(sitl->state.rpm[i] / 60.0f, freq_variation);
float phase_incr = motor_freq * 2 * M_PI / gyro_sample_hz[instance]; float phase_incr = motor_freq * 2 * M_PI / (gyro_sample_hz[instance] * nsamples);
float& phase = gyro_motor_phase[instance][i]; float &phase = gyro_motor_phase[instance][i];
phase += phase_incr; phase += phase_incr;
if (phase_incr > M_PI) { if (phase_incr > M_PI) {
phase -= 2 * M_PI; phase -= 2 * M_PI;
@ -180,34 +214,26 @@ void AP_InertialSensor_SITL::generate_gyro(uint8_t instance)
else if (phase_incr < -M_PI) { else if (phase_incr < -M_PI) {
phase += 2 * M_PI; phase += 2 * M_PI;
} }
p += sinf(phase) * calculate_noise(gyro_noise, noise_variation);
p += sinf(phase) * gyro_noise; q += sinf(phase) * calculate_noise(gyro_noise, noise_variation);
q += sinf(phase) * gyro_noise; r += sinf(phase) * calculate_noise(gyro_noise, noise_variation);
r += sinf(phase) * gyro_noise;
} }
} }
if (!vibe_freq.is_zero()) {
float t = AP_HAL::micros() * 1.0e-6f; Vector3f gyro = Vector3f(p, q, r);
p += sinf(t * 2 * M_PI * vibe_freq.x) * gyro_noise;
q += sinf(t * 2 * M_PI * vibe_freq.y) * gyro_noise; // add in gyro scaling
r += sinf(t * 2 * M_PI * vibe_freq.z) * gyro_noise; Vector3f scale = sitl->gyro_scale;
} gyro.x *= (1 + scale.x * 0.01f);
} gyro.y *= (1 + scale.y * 0.01f);
gyro.z *= (1 + scale.z * 0.01f);
Vector3f gyro = Vector3f(p, q, r);
_rotate_and_correct_gyro(gyro_instance[instance], gyro);
// add in gyro scaling gyro_accum += gyro;
Vector3f scale = sitl->gyro_scale; _notify_new_gyro_sensor_rate_sample(instance, gyro);
gyro.x *= (1 + scale.x * 0.01f);
gyro.y *= (1 + scale.y * 0.01f);
gyro.z *= (1 + scale.z * 0.01f);
_rotate_and_correct_gyro(gyro_instance[instance], gyro);
uint8_t nsamples = enable_fast_sampling(gyro_instance[instance]) ? 8 : 1;
for (uint8_t i = 0; i < nsamples; i++) {
_notify_new_gyro_raw_sample(gyro_instance[instance], gyro);
} }
gyro_accum /= nsamples;
_notify_new_gyro_raw_sample(gyro_instance[instance], gyro_accum);
} }
void AP_InertialSensor_SITL::timer_update(void) void AP_InertialSensor_SITL::timer_update(void)