ardupilot/Rover/ekf_check.cpp

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#include "Rover.h"
/**
*
* Detects failures of the ekf and triggers a failsafe
*
*/
#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 structure
static struct {
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;
// ekf_check - detects if ekf variance are out of tolerance and triggers failsafe
// should be called at 10hz
void Rover::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, or ekf check is disabled
if (!arming.is_armed() || (g.fs_ekf_thresh <= 0.0f)) {
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
if (ekf_over_threshold()) {
// if compass is not yet flagged as bad
if (!ekf_check_state.bad_variance) {
// increase counter
ekf_check_state.fail_count++;
// if counter above max then trigger failsafe
if (ekf_check_state.fail_count >= EKF_CHECK_ITERATIONS_MAX) {
// limit count from climbing too high
ekf_check_state.fail_count = EKF_CHECK_ITERATIONS_MAX;
ekf_check_state.bad_variance = true;
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AP::logger().Write_Error(LogErrorSubsystem::EKFCHECK,
LogErrorCode::EKFCHECK_BAD_VARIANCE);
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// 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
if (ekf_check_state.fail_count > 0) {
ekf_check_state.fail_count--;
// if variance is flagged as bad and the counter reaches zero then clear flag
if (ekf_check_state.bad_variance && ekf_check_state.fail_count == 0) {
ekf_check_state.bad_variance = false;
AP::logger().Write_Error(LogErrorSubsystem::EKFCHECK,
LogErrorCode::EKFCHECK_VARIANCE_CLEARED);
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// clear failsafe
failsafe_ekf_off_event();
}
}
}
// set AP_Notify flags
AP_Notify::flags.ekf_bad = ekf_check_state.bad_variance;
}
// returns true if the ekf's variance are over the tolerance
bool Rover::ekf_over_threshold()
{
// return false immediately if disabled
if (g.fs_ekf_thresh <= 0.0f) {
return false;
}
// use EKF to get variance
float position_variance, vel_variance, height_variance, tas_variance;
Vector3f mag_variance;
ahrs.get_variances(vel_variance, position_variance, height_variance, mag_variance, tas_variance);
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// 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++;
}
if (over_thresh_count >= 2) {
return true;
}
if (ekf_position_ok()) {
return false;
}
return true;
}
// ekf_position_ok - returns true if the ekf claims it's horizontal absolute position estimate is ok and home position is set
bool Rover::ekf_position_ok()
{
if (!ahrs.have_inertial_nav()) {
// do not allow navigation with dcm position
return false;
}
// get EKF filter status
nav_filter_status filt_status;
rover.ahrs.get_filter_status(filt_status);
// if disarmed we accept a predicted horizontal absolute or relative position
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if (!arming.is_armed()) {
return (filt_status.flags.horiz_pos_abs || filt_status.flags.pred_horiz_pos_abs || filt_status.flags.horiz_pos_rel || filt_status.flags.pred_horiz_pos_rel);
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} else {
// once armed we require a good absolute or relative position and EKF must not be in const_pos_mode
return ((filt_status.flags.horiz_pos_abs || filt_status.flags.horiz_pos_rel) && !filt_status.flags.const_pos_mode);
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}
}
// perform ekf failsafe
void Rover::failsafe_ekf_event()
{
// return immediately if ekf failsafe already triggered
if (failsafe.ekf) {
return;
}
// EKF failsafe event has occurred
failsafe.ekf = true;
AP::logger().Write_Error(LogErrorSubsystem::FAILSAFE_EKFINAV,
LogErrorCode::FAILSAFE_OCCURRED);
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// does this mode require position?
if (!control_mode->requires_position()) {
return;
}
// take action based on fs_ekf_action parameter
switch ((enum fs_ekf_action)g.fs_ekf_action.get()) {
case FS_EKF_DISABLE:
// do nothing
return;
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case FS_EKF_REPORT_ONLY:
break;
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case FS_EKF_HOLD:
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default:
set_mode(mode_hold, ModeReason::EKF_FAILSAFE);
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break;
}
gcs().send_text(MAV_SEVERITY_CRITICAL,"EKF failsafe");
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}
// failsafe_ekf_off_event - actions to take when EKF failsafe is cleared
void Rover::failsafe_ekf_off_event(void)
{
// return immediately if not in ekf failsafe
if (!failsafe.ekf) {
return;
}
failsafe.ekf = false;
AP::logger().Write_Error(LogErrorSubsystem::FAILSAFE_EKFINAV,
LogErrorCode::FAILSAFE_RESOLVED);
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gcs().send_text(MAV_SEVERITY_CRITICAL,"EKF failsafe cleared");
}