mirror of https://github.com/ArduPilot/ardupilot
475 lines
19 KiB
C++
475 lines
19 KiB
C++
#include <AP_HAL/AP_HAL.h>
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#if HAL_CPU_CLASS >= HAL_CPU_CLASS_150
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#include "AP_NavEKF2.h"
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#include "AP_NavEKF2_core.h"
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#include <AP_AHRS/AP_AHRS.h>
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#include <AP_Vehicle/AP_Vehicle.h>
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#include <GCS_MAVLink/GCS.h>
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#include <stdio.h>
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extern const AP_HAL::HAL& hal;
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/* Monitor GPS data to see if quality is good enough to initialise the EKF
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Monitor magnetometer innovations to to see if the heading is good enough to use GPS
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Return true if all criteria pass for 10 seconds
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We also record the failure reason so that prearm_failure_reason()
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can give a good report to the user on why arming is failing
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*/
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bool NavEKF2_core::calcGpsGoodToAlign(void)
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{
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const AP_GPS &gps = AP::gps();
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if (inFlight && assume_zero_sideslip() && !use_compass()) {
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// this is a special case where a plane has launched without magnetometer
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// is now in the air and needs to align yaw to the GPS and start navigating as soon as possible
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return true;
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}
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// User defined multiplier to be applied to check thresholds
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float checkScaler = 0.01f*(float)frontend->_gpsCheckScaler;
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// If we have good magnetometer consistency and bad innovations for longer than 5 seconds then we reset heading and field states
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// This enables us to handle large changes to the external magnetic field environment that occur before arming
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if ((magTestRatio.x <= 1.0f && magTestRatio.y <= 1.0f && yawTestRatio <= 1.0f) || !consistentMagData) {
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magYawResetTimer_ms = imuSampleTime_ms;
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}
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if ((imuSampleTime_ms - magYawResetTimer_ms > 5000) && !motorsArmed) {
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// request reset of heading and magnetic field states
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magYawResetRequest = true;
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// reset timer to ensure that bad magnetometer data cannot cause a heading reset more often than every 5 seconds
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magYawResetTimer_ms = imuSampleTime_ms;
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}
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// Check for significant change in GPS position if disarmed which indicates bad GPS
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// This check can only be used when the vehicle is stationary
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const struct Location &gpsloc = gps.location(); // Current location
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const float posFiltTimeConst = 10.0f; // time constant used to decay position drift
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// calculate time lapsesd since last update and limit to prevent numerical errors
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float deltaTime = constrain_float(float(imuDataDelayed.time_ms - lastPreAlignGpsCheckTime_ms)*0.001f,0.01f,posFiltTimeConst);
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lastPreAlignGpsCheckTime_ms = imuDataDelayed.time_ms;
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// Sum distance moved
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gpsDriftNE += location_diff(gpsloc_prev, gpsloc).length();
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gpsloc_prev = gpsloc;
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// Decay distance moved exponentially to zero
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gpsDriftNE *= (1.0f - deltaTime/posFiltTimeConst);
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// Clamp the fiter state to prevent excessive persistence of large transients
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gpsDriftNE = MIN(gpsDriftNE,10.0f);
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// Fail if more than 3 metres drift after filtering whilst on-ground
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// This corresponds to a maximum acceptable average drift rate of 0.3 m/s or single glitch event of 3m
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bool gpsDriftFail = (gpsDriftNE > 3.0f*checkScaler) && onGround && (frontend->_gpsCheck & MASK_GPS_POS_DRIFT);
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// Report check result as a text string and bitmask
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if (gpsDriftFail) {
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hal.util->snprintf(prearm_fail_string,
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sizeof(prearm_fail_string),
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"GPS drift %.1fm (needs %.1f)", (double)gpsDriftNE, (double)(3.0f*checkScaler));
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gpsCheckStatus.bad_horiz_drift = true;
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} else {
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gpsCheckStatus.bad_horiz_drift = false;
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}
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// Check that the vertical GPS vertical velocity is reasonable after noise filtering
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bool gpsVertVelFail;
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if (gps.have_vertical_velocity() && onGround) {
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// check that the average vertical GPS velocity is close to zero
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gpsVertVelFilt = 0.1f * gpsDataNew.vel.z + 0.9f * gpsVertVelFilt;
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gpsVertVelFilt = constrain_float(gpsVertVelFilt,-10.0f,10.0f);
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gpsVertVelFail = (fabsf(gpsVertVelFilt) > 0.3f*checkScaler) && (frontend->_gpsCheck & MASK_GPS_VERT_SPD);
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} else if ((frontend->_fusionModeGPS == 0) && !gps.have_vertical_velocity()) {
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// If the EKF settings require vertical GPS velocity and the receiver is not outputting it, then fail
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gpsVertVelFail = true;
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// if we have a 3D fix with no vertical velocity and
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// EK2_GPS_TYPE=0 then change it to 1. It means the GPS is not
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// capable of giving a vertical velocity
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if (gps.status() >= AP_GPS::GPS_OK_FIX_3D) {
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frontend->_fusionModeGPS.set(1);
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gcs().send_text(MAV_SEVERITY_WARNING, "EK2: Changed EK2_GPS_TYPE to 1");
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}
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} else {
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gpsVertVelFail = false;
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}
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// Report check result as a text string and bitmask
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if (gpsVertVelFail) {
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hal.util->snprintf(prearm_fail_string,
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sizeof(prearm_fail_string),
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"GPS vertical speed %.2fm/s (needs %.2f)", (double)fabsf(gpsVertVelFilt), (double)(0.3f*checkScaler));
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gpsCheckStatus.bad_vert_vel = true;
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} else {
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gpsCheckStatus.bad_vert_vel = false;
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}
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// Check that the horizontal GPS vertical velocity is reasonable after noise filtering
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// This check can only be used if the vehicle is stationary
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bool gpsHorizVelFail;
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if (onGround) {
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gpsHorizVelFilt = 0.1f * norm(gpsDataDelayed.vel.x,gpsDataDelayed.vel.y) + 0.9f * gpsHorizVelFilt;
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gpsHorizVelFilt = constrain_float(gpsHorizVelFilt,-10.0f,10.0f);
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gpsHorizVelFail = (fabsf(gpsHorizVelFilt) > 0.3f*checkScaler) && (frontend->_gpsCheck & MASK_GPS_HORIZ_SPD);
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} else {
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gpsHorizVelFail = false;
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}
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// Report check result as a text string and bitmask
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if (gpsHorizVelFail) {
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hal.util->snprintf(prearm_fail_string,
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sizeof(prearm_fail_string),
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"GPS horizontal speed %.2fm/s (needs %.2f)", (double)gpsDriftNE, (double)(0.3f*checkScaler));
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gpsCheckStatus.bad_horiz_vel = true;
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} else {
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gpsCheckStatus.bad_horiz_vel = false;
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}
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// fail if horiziontal position accuracy not sufficient
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float hAcc = 0.0f;
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bool hAccFail;
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if (gps.horizontal_accuracy(hAcc)) {
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hAccFail = (hAcc > 5.0f*checkScaler) && (frontend->_gpsCheck & MASK_GPS_POS_ERR);
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} else {
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hAccFail = false;
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}
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// Report check result as a text string and bitmask
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if (hAccFail) {
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hal.util->snprintf(prearm_fail_string,
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sizeof(prearm_fail_string),
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"GPS horiz error %.1fm (needs %.1f)", (double)hAcc, (double)(5.0f*checkScaler));
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gpsCheckStatus.bad_hAcc = true;
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} else {
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gpsCheckStatus.bad_hAcc = false;
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}
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// Check for vertical GPS accuracy
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float vAcc = 0.0f;
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bool vAccFail = false;
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if (gps.vertical_accuracy(vAcc)) {
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vAccFail = (vAcc > 7.5f * checkScaler) && (frontend->_gpsCheck & MASK_GPS_POS_ERR);
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}
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// Report check result as a text string and bitmask
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if (vAccFail) {
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hal.util->snprintf(prearm_fail_string,
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sizeof(prearm_fail_string),
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"GPS vert error %.1fm (needs < %.1f)", (double)vAcc, (double)(7.5f * checkScaler));
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gpsCheckStatus.bad_vAcc = true;
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} else {
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gpsCheckStatus.bad_vAcc = false;
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}
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// fail if reported speed accuracy greater than threshold
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bool gpsSpdAccFail = (gpsSpdAccuracy > 1.0f*checkScaler) && (frontend->_gpsCheck & MASK_GPS_SPD_ERR);
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// Report check result as a text string and bitmask
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if (gpsSpdAccFail) {
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hal.util->snprintf(prearm_fail_string,
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sizeof(prearm_fail_string),
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"GPS speed error %.1f (needs %.1f)", (double)gpsSpdAccuracy, (double)(1.0f*checkScaler));
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gpsCheckStatus.bad_sAcc = true;
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} else {
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gpsCheckStatus.bad_sAcc = false;
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}
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// fail if satellite geometry is poor
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bool hdopFail = (gps.get_hdop() > 250) && (frontend->_gpsCheck & MASK_GPS_HDOP);
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// Report check result as a text string and bitmask
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if (hdopFail) {
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hal.util->snprintf(prearm_fail_string, sizeof(prearm_fail_string),
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"GPS HDOP %.1f (needs 2.5)", (double)(0.01f * gps.get_hdop()));
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gpsCheckStatus.bad_hdop = true;
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} else {
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gpsCheckStatus.bad_hdop = false;
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}
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// fail if not enough sats
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bool numSatsFail = (gps.num_sats() < 6) && (frontend->_gpsCheck & MASK_GPS_NSATS);
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// Report check result as a text string and bitmask
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if (numSatsFail) {
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hal.util->snprintf(prearm_fail_string, sizeof(prearm_fail_string),
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"GPS numsats %u (needs 6)", gps.num_sats());
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gpsCheckStatus.bad_sats = true;
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} else {
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gpsCheckStatus.bad_sats = false;
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}
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// fail if magnetometer innovations are outside limits indicating bad yaw
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// with bad yaw we are unable to use GPS
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bool yawFail;
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if ((magTestRatio.x > 1.0f || magTestRatio.y > 1.0f || yawTestRatio > 1.0f) && (frontend->_gpsCheck & MASK_GPS_YAW_ERR)) {
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yawFail = true;
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} else {
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yawFail = false;
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}
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// Report check result as a text string and bitmask
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if (yawFail) {
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hal.util->snprintf(prearm_fail_string,
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sizeof(prearm_fail_string),
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"Mag yaw error x=%.1f y=%.1f",
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(double)magTestRatio.x,
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(double)magTestRatio.y);
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gpsCheckStatus.bad_yaw = true;
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} else {
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gpsCheckStatus.bad_yaw = false;
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}
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// assume failed first time through and notify user checks have started
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if (lastGpsVelFail_ms == 0) {
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hal.util->snprintf(prearm_fail_string, sizeof(prearm_fail_string), "EKF starting GPS checks");
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lastGpsVelFail_ms = imuSampleTime_ms;
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}
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// record time of fail
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if (gpsSpdAccFail || numSatsFail || hdopFail || hAccFail || vAccFail || yawFail || gpsDriftFail || gpsVertVelFail || gpsHorizVelFail) {
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lastGpsVelFail_ms = imuSampleTime_ms;
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}
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// continuous period without fail required to return a healthy status
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if (imuSampleTime_ms - lastGpsVelFail_ms > 10000) {
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return true;
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}
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return false;
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}
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// update inflight calculaton that determines if GPS data is good enough for reliable navigation
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void NavEKF2_core::calcGpsGoodForFlight(void)
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{
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// use a simple criteria based on the GPS receivers claimed speed accuracy and the EKF innovation consistency checks
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// set up varaibles and constants used by filter that is applied to GPS speed accuracy
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const float alpha1 = 0.2f; // coefficient for first stage LPF applied to raw speed accuracy data
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const float tau = 10.0f; // time constant (sec) of peak hold decay
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if (lastGpsCheckTime_ms == 0) {
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lastGpsCheckTime_ms = imuSampleTime_ms;
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}
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float dtLPF = (imuSampleTime_ms - lastGpsCheckTime_ms) * 1e-3f;
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lastGpsCheckTime_ms = imuSampleTime_ms;
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float alpha2 = constrain_float(dtLPF/tau,0.0f,1.0f);
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// get the receivers reported speed accuracy
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float gpsSpdAccRaw;
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if (!AP::gps().speed_accuracy(gpsSpdAccRaw)) {
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gpsSpdAccRaw = 0.0f;
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}
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// filter the raw speed accuracy using a LPF
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sAccFilterState1 = constrain_float((alpha1 * gpsSpdAccRaw + (1.0f - alpha1) * sAccFilterState1),0.0f,10.0f);
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// apply a peak hold filter to the LPF output
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sAccFilterState2 = MAX(sAccFilterState1,((1.0f - alpha2) * sAccFilterState2));
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// Apply a threshold test with hysteresis to the filtered GPS speed accuracy data
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if (sAccFilterState2 > 1.5f ) {
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gpsSpdAccPass = false;
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} else if(sAccFilterState2 < 1.0f) {
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gpsSpdAccPass = true;
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}
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// Apply a threshold test with hysteresis to the normalised position and velocity innovations
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// Require a fail for one second and a pass for 10 seconds to transition
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if (lastInnovFailTime_ms == 0) {
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lastInnovFailTime_ms = imuSampleTime_ms;
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lastInnovPassTime_ms = imuSampleTime_ms;
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}
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if (velTestRatio < 1.0f && posTestRatio < 1.0f) {
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lastInnovPassTime_ms = imuSampleTime_ms;
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} else if (velTestRatio > 0.7f || posTestRatio > 0.7f) {
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lastInnovFailTime_ms = imuSampleTime_ms;
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}
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if ((imuSampleTime_ms - lastInnovPassTime_ms) > 1000) {
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ekfInnovationsPass = false;
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} else if ((imuSampleTime_ms - lastInnovFailTime_ms) > 10000) {
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ekfInnovationsPass = true;
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}
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// both GPS speed accuracy and EKF innovations must pass
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gpsAccuracyGood = gpsSpdAccPass && ekfInnovationsPass;
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}
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// Detect if we are in flight or on ground
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void NavEKF2_core::detectFlight()
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{
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/*
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If we are a fly forward type vehicle (eg plane), then in-air status can be determined through a combination of speed and height criteria.
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Because of the differing certainty requirements of algorithms that need the in-flight / on-ground status we use two booleans where
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onGround indicates a high certainty we are not flying and inFlight indicates a high certainty we are flying. It is possible for
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both onGround and inFlight to be false if the status is uncertain, but they cannot both be true.
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If we are a plane as indicated by the assume_zero_sideslip() status, then different logic is used
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TODO - this logic should be moved out of the EKF and into the flight vehicle code.
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*/
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if (assume_zero_sideslip()) {
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// To be confident we are in the air we use a criteria which combines arm status, ground speed, airspeed and height change
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float gndSpdSq = sq(gpsDataDelayed.vel.x) + sq(gpsDataDelayed.vel.y);
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bool highGndSpd = false;
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bool highAirSpd = false;
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bool largeHgtChange = false;
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// trigger at 8 m/s airspeed
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if (_ahrs->airspeed_sensor_enabled()) {
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const AP_Airspeed *airspeed = _ahrs->get_airspeed();
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if (airspeed->get_airspeed() * airspeed->get_EAS2TAS() > 10.0f) {
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highAirSpd = true;
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}
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}
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// trigger at 10 m/s GPS velocity, but not if GPS is reporting bad velocity errors
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if (gndSpdSq > 100.0f && gpsSpdAccuracy < 1.0f) {
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highGndSpd = true;
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}
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// trigger if more than 10m away from initial height
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if (fabsf(hgtMea) > 10.0f) {
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largeHgtChange = true;
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}
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// Determine to a high certainty we are flying
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if (motorsArmed && highGndSpd && (highAirSpd || largeHgtChange)) {
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onGround = false;
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inFlight = true;
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}
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// if is possible we are in flight, set the time this condition was last detected
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if (motorsArmed && (highGndSpd || highAirSpd || largeHgtChange)) {
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airborneDetectTime_ms = imuSampleTime_ms;
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onGround = false;
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}
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// Determine to a high certainty we are not flying
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// after 5 seconds of not detecting a possible flight condition or we are disarmed, we transition to on-ground mode
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if(!motorsArmed || ((imuSampleTime_ms - airborneDetectTime_ms) > 5000)) {
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onGround = true;
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inFlight = false;
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}
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} else {
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// Non fly forward vehicle, so can only use height and motor arm status
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// If the motors are armed then we could be flying and if they are not armed then we are definitely not flying
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if (motorsArmed) {
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onGround = false;
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} else {
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inFlight = false;
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onGround = true;
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}
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if (!onGround) {
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// If height has increased since exiting on-ground, then we definitely are flying
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if ((stateStruct.position.z - posDownAtTakeoff) < -1.5f) {
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inFlight = true;
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}
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// If rangefinder has increased since exiting on-ground, then we definitely are flying
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if ((rangeDataNew.rng - rngAtStartOfFlight) > 0.5f) {
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inFlight = true;
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}
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// If more than 5 seconds since likely_flying was set
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// true, then set inFlight true
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if (_ahrs->get_time_flying_ms() > 5000) {
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inFlight = true;
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}
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}
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}
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// store current on-ground and in-air status for next time
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prevOnGround = onGround;
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prevInFlight = inFlight;
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// Store vehicle height and range prior to takeoff for use in post takeoff checks
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if (onGround) {
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// store vertical position at start of flight to use as a reference for ground relative checks
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posDownAtTakeoff = stateStruct.position.z;
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// store the range finder measurement which will be used as a reference to detect when we have taken off
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rngAtStartOfFlight = rangeDataNew.rng;
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// if the magnetic field states have been set, then continue to update the vertical position
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// quaternion and yaw innovation snapshots to use as a reference when we start to fly.
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if (magStateInitComplete) {
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posDownAtLastMagReset = stateStruct.position.z;
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quatAtLastMagReset = stateStruct.quat;
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yawInnovAtLastMagReset = innovYaw;
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}
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}
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}
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// determine if a takeoff is expected so that we can compensate for expected barometer errors due to ground effect
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bool NavEKF2_core::getTakeoffExpected()
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{
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if (expectGndEffectTakeoff && imuSampleTime_ms - takeoffExpectedSet_ms > frontend->gndEffectTimeout_ms) {
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expectGndEffectTakeoff = false;
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}
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return expectGndEffectTakeoff;
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}
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// called by vehicle code to specify that a takeoff is happening
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// causes the EKF to compensate for expected barometer errors due to ground effect
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void NavEKF2_core::setTakeoffExpected(bool val)
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{
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takeoffExpectedSet_ms = imuSampleTime_ms;
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expectGndEffectTakeoff = val;
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}
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// determine if a touchdown is expected so that we can compensate for expected barometer errors due to ground effect
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bool NavEKF2_core::getTouchdownExpected()
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{
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if (expectGndEffectTouchdown && imuSampleTime_ms - touchdownExpectedSet_ms > frontend->gndEffectTimeout_ms) {
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expectGndEffectTouchdown = false;
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}
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return expectGndEffectTouchdown;
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}
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// called by vehicle code to specify that a touchdown is expected to happen
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// causes the EKF to compensate for expected barometer errors due to ground effect
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void NavEKF2_core::setTouchdownExpected(bool val)
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|
{
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touchdownExpectedSet_ms = imuSampleTime_ms;
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expectGndEffectTouchdown = val;
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}
|
|
|
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// Set to true if the terrain underneath is stable enough to be used as a height reference
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|
// in combination with a range finder. Set to false if the terrain underneath the vehicle
|
|
// cannot be used as a height reference
|
|
void NavEKF2_core::setTerrainHgtStable(bool val)
|
|
{
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|
terrainHgtStableSet_ms = imuSampleTime_ms;
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|
terrainHgtStable = val;
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|
}
|
|
|
|
// Detect takeoff for optical flow navigation
|
|
void NavEKF2_core::detectOptFlowTakeoff(void)
|
|
{
|
|
if (!onGround && !takeOffDetected && (imuSampleTime_ms - timeAtArming_ms) > 1000) {
|
|
// we are no longer confidently on the ground so check the range finder and gyro for signs of takeoff
|
|
const AP_InertialSensor &ins = AP::ins();
|
|
Vector3f angRateVec;
|
|
Vector3f gyroBias;
|
|
getGyroBias(gyroBias);
|
|
bool dual_ins = ins.get_gyro_health(0) && ins.get_gyro_health(1);
|
|
if (dual_ins) {
|
|
angRateVec = (ins.get_gyro(0) + ins.get_gyro(1)) * 0.5f - gyroBias;
|
|
} else {
|
|
angRateVec = ins.get_gyro() - gyroBias;
|
|
}
|
|
|
|
takeOffDetected = (takeOffDetected || (angRateVec.length() > 0.1f) || (rangeDataNew.rng > (rngAtStartOfFlight + 0.1f)));
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|
} else if (onGround) {
|
|
// we are confidently on the ground so set the takeoff detected status to false
|
|
takeOffDetected = false;
|
|
}
|
|
}
|
|
|
|
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|
#endif // HAL_CPU_CLASS
|