ardupilot/ArduCopter/ekf_check.cpp

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#include "Copter.h"
/**
*
* Detects failures of the ekf or inertial nav system triggers an alert
* to the pilot and helps take countermeasures
*
*/
#ifndef EKF_CHECK_ITERATIONS_MAX
# define EKF_CHECK_ITERATIONS_MAX 10 // 1 second (ie. 10 iterations at 10hz) of bad variances signals a failure
#endif
#ifndef EKF_CHECK_WARNING_TIME
# define EKF_CHECK_WARNING_TIME (30*1000) // warning text messages are sent to ground no more than every 30 seconds
#endif
////////////////////////////////////////////////////////////////////////////////
// EKF_check strucutre
////////////////////////////////////////////////////////////////////////////////
static struct {
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uint8_t fail_count; // number of iterations ekf or dcm have been out of tolerances
uint8_t bad_variance : 1; // true if ekf should be considered untrusted (fail_count has exceeded EKF_CHECK_ITERATIONS_MAX)
uint32_t last_warn_time; // system time of last warning in milliseconds. Used to throttle text warnings sent to GCS
} ekf_check_state;
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// ekf_check - detects if ekf variance are out of tolerance and triggers failsafe
// should be called at 10hz
void Copter::ekf_check()
{
// exit immediately if ekf has no origin yet - this assumes the origin can never become unset
Location temp_loc;
if (!ahrs.get_origin(temp_loc)) {
return;
}
// return immediately if motors are not armed, ekf check is disabled, not using ekf or usb is connected
if (!motors->armed() || ap.usb_connected || (g.fs_ekf_thresh <= 0.0f)) {
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ekf_check_state.fail_count = 0;
ekf_check_state.bad_variance = false;
AP_Notify::flags.ekf_bad = ekf_check_state.bad_variance;
failsafe_ekf_off_event(); // clear failsafe
return;
}
// compare compass and velocity variance vs threshold
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if (ekf_over_threshold()) {
// if compass is not yet flagged as bad
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if (!ekf_check_state.bad_variance) {
// increase counter
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ekf_check_state.fail_count++;
// if counter above max then trigger failsafe
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if (ekf_check_state.fail_count >= EKF_CHECK_ITERATIONS_MAX) {
// limit count from climbing too high
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ekf_check_state.fail_count = EKF_CHECK_ITERATIONS_MAX;
ekf_check_state.bad_variance = true;
// log an error in the dataflash
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Log_Write_Error(ERROR_SUBSYSTEM_EKFCHECK, ERROR_CODE_EKFCHECK_BAD_VARIANCE);
// send message to gcs
if ((AP_HAL::millis() - ekf_check_state.last_warn_time) > EKF_CHECK_WARNING_TIME) {
gcs().send_text(MAV_SEVERITY_CRITICAL,"EKF variance");
ekf_check_state.last_warn_time = AP_HAL::millis();
}
failsafe_ekf_event();
}
}
} else {
// reduce counter
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if (ekf_check_state.fail_count > 0) {
ekf_check_state.fail_count--;
// if compass is flagged as bad and the counter reaches zero then clear flag
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if (ekf_check_state.bad_variance && ekf_check_state.fail_count == 0) {
ekf_check_state.bad_variance = false;
// log recovery in the dataflash
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Log_Write_Error(ERROR_SUBSYSTEM_EKFCHECK, ERROR_CODE_EKFCHECK_VARIANCE_CLEARED);
// clear failsafe
failsafe_ekf_off_event();
}
}
}
// set AP_Notify flags
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AP_Notify::flags.ekf_bad = ekf_check_state.bad_variance;
// To-Do: add ekf variances to extended status
}
// ekf_over_threshold - returns true if the ekf's variance are over the tolerance
bool Copter::ekf_over_threshold()
{
// return false immediately if disabled
if (g.fs_ekf_thresh <= 0.0f) {
return false;
}
// return true immediately if position is bad
if (!ekf_position_ok() && !optflow_position_ok()) {
return true;
}
// use EKF to get variance
float position_variance, vel_variance, height_variance, tas_variance;
Vector3f mag_variance;
Vector2f offset;
ahrs.get_variances(vel_variance, position_variance, height_variance, mag_variance, tas_variance, offset);
// return true if two of compass, velocity and position variances are over the threshold
uint8_t over_thresh_count = 0;
if (mag_variance.length() >= g.fs_ekf_thresh) {
over_thresh_count++;
}
if (vel_variance >= g.fs_ekf_thresh) {
over_thresh_count++;
}
if (position_variance >= g.fs_ekf_thresh) {
over_thresh_count++;
}
return (over_thresh_count >= 2);
}
// failsafe_ekf_event - perform ekf failsafe
void Copter::failsafe_ekf_event()
{
// return immediately if ekf failsafe already triggered
if (failsafe.ekf) {
return;
}
// do nothing if motors disarmed
if (!motors->armed()) {
return;
}
// do nothing if not in GPS flight mode and ekf-action is not land-even-stabilize
if ((control_mode != LAND) && !mode_requires_GPS(control_mode) && (g.fs_ekf_action != FS_EKF_ACTION_LAND_EVEN_STABILIZE)) {
return;
}
// EKF failsafe event has occurred
failsafe.ekf = true;
Log_Write_Error(ERROR_SUBSYSTEM_FAILSAFE_EKFINAV, ERROR_CODE_FAILSAFE_OCCURRED);
// take action based on fs_ekf_action parameter
switch (g.fs_ekf_action) {
case FS_EKF_ACTION_ALTHOLD:
// AltHold
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if (failsafe.radio || !set_mode(ALT_HOLD, MODE_REASON_EKF_FAILSAFE)) {
set_mode_land_with_pause(MODE_REASON_EKF_FAILSAFE);
}
break;
default:
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set_mode_land_with_pause(MODE_REASON_EKF_FAILSAFE);
break;
}
// if flight mode is already LAND ensure it's not the GPS controlled LAND
if (control_mode == LAND) {
land_do_not_use_GPS();
}
}
// failsafe_ekf_off_event - actions to take when EKF failsafe is cleared
void Copter::failsafe_ekf_off_event(void)
{
// return immediately if not in ekf failsafe
if (!failsafe.ekf) {
return;
}
// clear flag and log recovery
failsafe.ekf = false;
Log_Write_Error(ERROR_SUBSYSTEM_FAILSAFE_EKFINAV, ERROR_CODE_FAILSAFE_RESOLVED);
}
// check for ekf yaw reset and adjust target heading, also log position reset
void Copter::check_ekf_reset()
{
// check for yaw reset
float yaw_angle_change_rad = 0.0f;
uint32_t new_ekfYawReset_ms = ahrs.getLastYawResetAngle(yaw_angle_change_rad);
if (new_ekfYawReset_ms != ekfYawReset_ms) {
attitude_control->shift_ef_yaw_target(ToDeg(yaw_angle_change_rad) * 100.0f);
ekfYawReset_ms = new_ekfYawReset_ms;
Log_Write_Event(DATA_EKF_YAW_RESET);
}
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#if AP_AHRS_NAVEKF_AVAILABLE
// check for change in primary EKF (log only, AC_WPNav handles position target adjustment)
if ((EKF2.getPrimaryCoreIndex() != ekf_primary_core) && (EKF2.getPrimaryCoreIndex() != -1)) {
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ekf_primary_core = EKF2.getPrimaryCoreIndex();
Log_Write_Error(ERROR_SUBSYSTEM_EKF_PRIMARY, ekf_primary_core);
gcs().send_text(MAV_SEVERITY_WARNING, "EKF primary changed:%d\n", (unsigned)ekf_primary_core);
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}
#endif
}