#include #include "AP_NavEKF3.h" #include "AP_NavEKF3_core.h" #include #include #include #include extern const AP_HAL::HAL& hal; /* Monitor GPS data to see if quality is good enough to initialise the EKF Monitor magnetometer innovations to see if the heading is good enough to use GPS Return true if all criteria pass for 10 seconds We also record the failure reason so that prearm_failure_reason() can give a good report to the user on why arming is failing */ void NavEKF3_core::calcGpsGoodToAlign(void) { if (inFlight && assume_zero_sideslip() && !use_compass()) { // this is a special case where a plane has launched without magnetometer // is now in the air and needs to align yaw to the GPS and start navigating as soon as possible gpsGoodToAlign = true; return; } // User defined multiplier to be applied to check thresholds float checkScaler = 0.01f*(float)frontend->_gpsCheckScaler; if (gpsGoodToAlign) { /* if we have already passed GPS alignment checks then raise the check threshold so that we have some hysterisis and don't continuously change from able to arm to not able to arm */ checkScaler *= 1.3f; } // If we have good magnetometer consistency and bad innovations for longer than 5 seconds then we reset heading and field states // This enables us to handle large changes to the external magnetic field environment that occur before arming if ((magTestRatio.x <= 1.0f && magTestRatio.y <= 1.0f && yawTestRatio <= 1.0f) || !consistentMagData) { magYawResetTimer_ms = imuSampleTime_ms; } if ((imuSampleTime_ms - magYawResetTimer_ms > 5000) && !motorsArmed) { // request reset of heading and magnetic field states magYawResetRequest = true; // reset timer to ensure that bad magnetometer data cannot cause a heading reset more often than every 5 seconds magYawResetTimer_ms = imuSampleTime_ms; } // Check for significant change in GPS position if disarmed which indicates bad GPS // This check can only be used when the vehicle is stationary const AP_GPS &gps = AP::gps(); const struct Location &gpsloc = gps.location(); // Current location const float posFiltTimeConst = 10.0f; // time constant used to decay position drift // calculate time lapsed since last update and limit to prevent numerical errors float deltaTime = constrain_float(float(imuDataDelayed.time_ms - lastPreAlignGpsCheckTime_ms)*0.001f,0.01f,posFiltTimeConst); lastPreAlignGpsCheckTime_ms = imuDataDelayed.time_ms; // Sum distance moved gpsDriftNE += gpsloc_prev.get_distance(gpsloc); gpsloc_prev = gpsloc; // Decay distance moved exponentially to zero gpsDriftNE *= (1.0f - deltaTime/posFiltTimeConst); // Clamp the filter state to prevent excessive persistence of large transients gpsDriftNE = MIN(gpsDriftNE,10.0f); // Fail if more than 3 metres drift after filtering whilst on-ground // This corresponds to a maximum acceptable average drift rate of 0.3 m/s or single glitch event of 3m bool gpsDriftFail = (gpsDriftNE > 3.0f*checkScaler) && onGround && (frontend->_gpsCheck & MASK_GPS_POS_DRIFT); // Report check result as a text string and bitmask if (gpsDriftFail) { hal.util->snprintf(prearm_fail_string, sizeof(prearm_fail_string), "GPS drift %.1fm (needs %.1f)", (double)gpsDriftNE, (double)(3.0f*checkScaler)); gpsCheckStatus.bad_horiz_drift = true; } else { gpsCheckStatus.bad_horiz_drift = false; } // Check that the vertical GPS vertical velocity is reasonable after noise filtering bool gpsVertVelFail; if (gps.have_vertical_velocity() && onGround) { // check that the average vertical GPS velocity is close to zero gpsVertVelFilt = 0.1f * gpsDataNew.vel.z + 0.9f * gpsVertVelFilt; gpsVertVelFilt = constrain_float(gpsVertVelFilt,-10.0f,10.0f); gpsVertVelFail = (fabsf(gpsVertVelFilt) > 0.3f*checkScaler) && (frontend->_gpsCheck & MASK_GPS_VERT_SPD); } else if ((frontend->_fusionModeGPS == 0) && !gps.have_vertical_velocity()) { // If the EKF settings require vertical GPS velocity and the receiver is not outputting it, then fail gpsVertVelFail = true; // if we have a 3D fix with no vertical velocity and // EK3_GPS_TYPE=0 then change it to 1. It means the GPS is not // capable of giving a vertical velocity if (gps.status() >= AP_GPS::GPS_OK_FIX_3D) { frontend->_fusionModeGPS.set(1); gcs().send_text(MAV_SEVERITY_WARNING, "EK3: Changed EK3_GPS_TYPE to 1"); } } else { gpsVertVelFail = false; } // Report check result as a text string and bitmask if (gpsVertVelFail) { hal.util->snprintf(prearm_fail_string, sizeof(prearm_fail_string), "GPS vertical speed %.2fm/s (needs %.2f)", (double)fabsf(gpsVertVelFilt), (double)(0.3f*checkScaler)); gpsCheckStatus.bad_vert_vel = true; } else { gpsCheckStatus.bad_vert_vel = false; } // Check that the horizontal GPS vertical velocity is reasonable after noise filtering // This check can only be used if the vehicle is stationary bool gpsHorizVelFail; if (onGround) { gpsHorizVelFilt = 0.1f * norm(gpsDataDelayed.vel.x,gpsDataDelayed.vel.y) + 0.9f * gpsHorizVelFilt; gpsHorizVelFilt = constrain_float(gpsHorizVelFilt,-10.0f,10.0f); gpsHorizVelFail = (fabsf(gpsHorizVelFilt) > 0.3f*checkScaler) && (frontend->_gpsCheck & MASK_GPS_HORIZ_SPD); } else { gpsHorizVelFail = false; } // Report check result as a text string and bitmask if (gpsHorizVelFail) { hal.util->snprintf(prearm_fail_string, sizeof(prearm_fail_string), "GPS horizontal speed %.2fm/s (needs %.2f)", (double)gpsDriftNE, (double)(0.3f*checkScaler)); gpsCheckStatus.bad_horiz_vel = true; } else { gpsCheckStatus.bad_horiz_vel = false; } // fail if horiziontal position accuracy not sufficient float hAcc = 0.0f; bool hAccFail; if (gps.horizontal_accuracy(hAcc)) { hAccFail = (hAcc > 5.0f*checkScaler) && (frontend->_gpsCheck & MASK_GPS_POS_ERR); } else { hAccFail = false; } // Report check result as a text string and bitmask if (hAccFail) { hal.util->snprintf(prearm_fail_string, sizeof(prearm_fail_string), "GPS horiz error %.1fm (needs %.1f)", (double)hAcc, (double)(5.0f*checkScaler)); gpsCheckStatus.bad_hAcc = true; } else { gpsCheckStatus.bad_hAcc = false; } // Check for vertical GPS accuracy float vAcc = 0.0f; bool vAccFail = false; if (gps.vertical_accuracy(vAcc)) { vAccFail = (vAcc > 7.5f * checkScaler) && (frontend->_gpsCheck & MASK_GPS_POS_ERR); } // Report check result as a text string and bitmask if (vAccFail) { hal.util->snprintf(prearm_fail_string, sizeof(prearm_fail_string), "GPS vert error %.1fm (needs < %.1f)", (double)vAcc, (double)(7.5f * checkScaler)); gpsCheckStatus.bad_vAcc = true; } else { gpsCheckStatus.bad_vAcc = false; } // fail if reported speed accuracy greater than threshold bool gpsSpdAccFail = (gpsSpdAccuracy > 1.0f*checkScaler) && (frontend->_gpsCheck & MASK_GPS_SPD_ERR); // Report check result as a text string and bitmask if (gpsSpdAccFail) { hal.util->snprintf(prearm_fail_string, sizeof(prearm_fail_string), "GPS speed error %.1f (needs < %.1f)", (double)gpsSpdAccuracy, (double)(1.0f*checkScaler)); gpsCheckStatus.bad_sAcc = true; } else { gpsCheckStatus.bad_sAcc = false; } // fail if satellite geometry is poor bool hdopFail = (gps.get_hdop() > 250) && (frontend->_gpsCheck & MASK_GPS_HDOP); // Report check result as a text string and bitmask if (hdopFail) { hal.util->snprintf(prearm_fail_string, sizeof(prearm_fail_string), "GPS HDOP %.1f (needs 2.5)", (double)(0.01f * gps.get_hdop())); gpsCheckStatus.bad_hdop = true; } else { gpsCheckStatus.bad_hdop = false; } // fail if not enough sats bool numSatsFail = (gps.num_sats() < 6) && (frontend->_gpsCheck & MASK_GPS_NSATS); // Report check result as a text string and bitmask if (numSatsFail) { hal.util->snprintf(prearm_fail_string, sizeof(prearm_fail_string), "GPS numsats %u (needs 6)", gps.num_sats()); gpsCheckStatus.bad_sats = true; } else { gpsCheckStatus.bad_sats = false; } // fail if magnetometer innovations are outside limits indicating bad yaw // with bad yaw we are unable to use GPS bool yawFail; if ((magTestRatio.x > 1.0f || magTestRatio.y > 1.0f || yawTestRatio > 1.0f) && (frontend->_gpsCheck & MASK_GPS_YAW_ERR)) { yawFail = true; } else { yawFail = false; } // Report check result as a text string and bitmask if (yawFail) { hal.util->snprintf(prearm_fail_string, sizeof(prearm_fail_string), "Mag yaw error x=%.1f y=%.1f", (double)magTestRatio.x, (double)magTestRatio.y); gpsCheckStatus.bad_yaw = true; } else { gpsCheckStatus.bad_yaw = false; } // assume failed first time through and notify user checks have started if (lastGpsVelFail_ms == 0) { hal.util->snprintf(prearm_fail_string, sizeof(prearm_fail_string), "EKF starting GPS checks"); lastGpsVelFail_ms = imuSampleTime_ms; } // record time of pass or fail if (gpsSpdAccFail || numSatsFail || hdopFail || hAccFail || vAccFail || yawFail || gpsDriftFail || gpsVertVelFail || gpsHorizVelFail) { lastGpsVelFail_ms = imuSampleTime_ms; } else { lastGpsVelPass_ms = imuSampleTime_ms; } // continuous period of 10s without fail required to set healthy // continuous period of 5s without pass required to set unhealthy if (!gpsGoodToAlign && imuSampleTime_ms - lastGpsVelFail_ms > 10000) { gpsGoodToAlign = true; } else if (gpsGoodToAlign && imuSampleTime_ms - lastGpsVelPass_ms > 5000) { gpsGoodToAlign = false; } } // update inflight calculaton that determines if GPS data is good enough for reliable navigation void NavEKF3_core::calcGpsGoodForFlight(void) { // use a simple criteria based on the GPS receivers claimed speed accuracy and the EKF innovation consistency checks // set up varaibles and constants used by filter that is applied to GPS speed accuracy const float alpha1 = 0.2f; // coefficient for first stage LPF applied to raw speed accuracy data const float tau = 10.0f; // time constant (sec) of peak hold decay if (lastGpsCheckTime_ms == 0) { lastGpsCheckTime_ms = imuSampleTime_ms; } float dtLPF = (imuSampleTime_ms - lastGpsCheckTime_ms) * 1e-3f; lastGpsCheckTime_ms = imuSampleTime_ms; float alpha2 = constrain_float(dtLPF/tau,0.0f,1.0f); // get the receivers reported speed accuracy float gpsSpdAccRaw; if (!AP::gps().speed_accuracy(gpsSpdAccRaw)) { gpsSpdAccRaw = 0.0f; } // filter the raw speed accuracy using a LPF sAccFilterState1 = constrain_float((alpha1 * gpsSpdAccRaw + (1.0f - alpha1) * sAccFilterState1),0.0f,10.0f); // apply a peak hold filter to the LPF output sAccFilterState2 = MAX(sAccFilterState1,((1.0f - alpha2) * sAccFilterState2)); // Apply a threshold test with hysteresis to the filtered GPS speed accuracy data if (sAccFilterState2 > 1.5f ) { gpsSpdAccPass = false; } else if(sAccFilterState2 < 1.0f) { gpsSpdAccPass = true; } // Apply a threshold test with hysteresis to the normalised position and velocity innovations // Require a fail for one second and a pass for 10 seconds to transition if (lastInnovFailTime_ms == 0) { lastInnovFailTime_ms = imuSampleTime_ms; lastInnovPassTime_ms = imuSampleTime_ms; } if (velTestRatio < 1.0f && posTestRatio < 1.0f) { lastInnovPassTime_ms = imuSampleTime_ms; } else if (velTestRatio > 0.7f || posTestRatio > 0.7f) { lastInnovFailTime_ms = imuSampleTime_ms; } if ((imuSampleTime_ms - lastInnovPassTime_ms) > 1000) { ekfInnovationsPass = false; } else if ((imuSampleTime_ms - lastInnovFailTime_ms) > 10000) { ekfInnovationsPass = true; } // both GPS speed accuracy and EKF innovations must pass gpsAccuracyGood = gpsSpdAccPass && ekfInnovationsPass; } // Detect if we are in flight or on ground void NavEKF3_core::detectFlight() { /* 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. Because of the differing certainty requirements of algorithms that need the in-flight / on-ground status we use two booleans where onGround indicates a high certainty we are not flying and inFlight indicates a high certainty we are flying. It is possible for both onGround and inFlight to be false if the status is uncertain, but they cannot both be true. If we are a plane as indicated by the assume_zero_sideslip() status, then different logic is used TODO - this logic should be moved out of the EKF and into the flight vehicle code. */ if (assume_zero_sideslip()) { // To be confident we are in the air we use a criteria which combines arm status, ground speed, airspeed and height change float gndSpdSq = sq(gpsDataDelayed.vel.x) + sq(gpsDataDelayed.vel.y); bool highGndSpd = false; bool highAirSpd = false; bool largeHgtChange = false; // trigger at 8 m/s airspeed if (_ahrs->airspeed_sensor_enabled()) { const AP_Airspeed *airspeed = _ahrs->get_airspeed(); if (airspeed->get_airspeed() * AP::ahrs().get_EAS2TAS() > 10.0f) { highAirSpd = true; } } // trigger at 10 m/s GPS velocity, but not if GPS is reporting bad velocity errors if (gndSpdSq > 100.0f && gpsSpdAccuracy < 1.0f) { highGndSpd = true; } // trigger if more than 10m away from initial height if (fabsf(hgtMea) > 10.0f) { largeHgtChange = true; } // Determine to a high certainty we are flying if (motorsArmed && highGndSpd && (highAirSpd || largeHgtChange)) { onGround = false; inFlight = true; } // if is possible we are in flight, set the time this condition was last detected if (motorsArmed && (highGndSpd || highAirSpd || largeHgtChange)) { airborneDetectTime_ms = imuSampleTime_ms; onGround = false; } // Determine to a high certainty we are not flying // after 5 seconds of not detecting a possible flight condition or we are disarmed, we transition to on-ground mode if(!motorsArmed || ((imuSampleTime_ms - airborneDetectTime_ms) > 5000)) { onGround = true; inFlight = false; } } else { // Non fly forward vehicle, so can only use height and motor arm status // If the motors are armed then we could be flying and if they are not armed then we are definitely not flying if (motorsArmed) { onGround = false; } else { inFlight = false; onGround = true; } if (!onGround) { // If height has increased since exiting on-ground, then we definitely are flying if ((stateStruct.position.z - posDownAtTakeoff) < -1.5f) { inFlight = true; } // If rangefinder has increased since exiting on-ground, then we definitely are flying if ((rangeDataNew.rng - rngAtStartOfFlight) > 0.5f) { inFlight = true; } // If more than 5 seconds since likely_flying was set // true, then set inFlight true if (_ahrs->get_time_flying_ms() > 5000) { inFlight = true; } } } // store current on-ground and in-air status for next time prevOnGround = onGround; prevInFlight = inFlight; // Store vehicle height and range prior to takeoff for use in post takeoff checks if (onGround) { // store vertical position at start of flight to use as a reference for ground relative checks posDownAtTakeoff = stateStruct.position.z; // store the range finder measurement which will be used as a reference to detect when we have taken off rngAtStartOfFlight = rangeDataNew.rng; // if the magnetic field states have been set, then continue to update the vertical position // quaternion and yaw innovation snapshots to use as a reference when we start to fly. if (magStateInitComplete) { posDownAtLastMagReset = stateStruct.position.z; quatAtLastMagReset = stateStruct.quat; yawInnovAtLastMagReset = innovYaw; } } } // determine if a takeoff is expected so that we can compensate for expected barometer errors due to ground effect bool NavEKF3_core::getTakeoffExpected() { if (expectGndEffectTakeoff && imuSampleTime_ms - takeoffExpectedSet_ms > frontend->gndEffectTimeout_ms) { expectGndEffectTakeoff = false; } return expectGndEffectTakeoff; } // called by vehicle code to specify that a takeoff is happening // causes the EKF to compensate for expected barometer errors due to ground effect void NavEKF3_core::setTakeoffExpected(bool val) { takeoffExpectedSet_ms = imuSampleTime_ms; expectGndEffectTakeoff = val; } // determine if a touchdown is expected so that we can compensate for expected barometer errors due to ground effect bool NavEKF3_core::getTouchdownExpected() { if (expectGndEffectTouchdown && imuSampleTime_ms - touchdownExpectedSet_ms > frontend->gndEffectTimeout_ms) { expectGndEffectTouchdown = false; } return expectGndEffectTouchdown; } // called by vehicle code to specify that a touchdown is expected to happen // causes the EKF to compensate for expected barometer errors due to ground effect void NavEKF3_core::setTouchdownExpected(bool val) { touchdownExpectedSet_ms = imuSampleTime_ms; expectGndEffectTouchdown = val; } // Set to true if the terrain underneath is stable enough to be used as a height reference // in combination with a range finder. Set to false if the terrain underneath the vehicle // cannot be used as a height reference void NavEKF3_core::setTerrainHgtStable(bool val) { terrainHgtStableSet_ms = imuSampleTime_ms; terrainHgtStable = val; } // Detect takeoff for optical flow navigation void NavEKF3_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.use_gyro(0) && ins.use_gyro(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))); } else if (onGround) { // we are confidently on the ground so set the takeoff detected status to false takeOffDetected = false; } }