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AP_NavEKF2: fixed use of antenna position when switching GPS primary 

when GPS primary switches we were using a position which had not been
corrected for antenna offset. This was used for calculating the reset
for sensor change.

This fixes that (trivial fix) and also fixes a similar issue on
position reset
This commit is contained in:
Andrew Tridgell 2020-01-26 17:06:58 +11:00 committed by Randy Mackay
parent 31b98d5d97
commit 2cf3ad4a3d
2 changed files with 46 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

68
libraries/AP_NavEKF2/AP_NavEKF2_PosVelFusion.cpp
View File

@ -28,6 +28,9 @@ void NavEKF2_core::ResetVelocity(void)
zeroRows(P,3,4);
zeroCols(P,3,4);
gps_elements gps_corrected = gpsDataNew;
CorrectGPSForAntennaOffset(gps_corrected);
if (PV_AidingMode != AID_ABSOLUTE) {
stateStruct.velocity.zero();
// set the variances using the measurement noise parameter
@ -35,8 +38,8 @@ void NavEKF2_core::ResetVelocity(void)
} else {
// reset horizontal velocity states to the GPS velocity if available
if (imuSampleTime_ms - lastTimeGpsReceived_ms < 250) {
stateStruct.velocity.x = gpsDataNew.vel.x;
stateStruct.velocity.y = gpsDataNew.vel.y;
stateStruct.velocity.x = gps_corrected.vel.x;
stateStruct.velocity.y = gps_corrected.vel.y;
// set the variances using the reported GPS speed accuracy
P[4][4] = P[3][3] = sq(MAX(frontend->_gpsHorizVelNoise,gpsSpdAccuracy));
// clear the timeout flags and counters
@ -82,6 +85,9 @@ void NavEKF2_core::ResetPosition(void)
zeroRows(P,6,7);
zeroCols(P,6,7);
gps_elements gps_corrected = gpsDataNew;
CorrectGPSForAntennaOffset(gps_corrected);
if (PV_AidingMode != AID_ABSOLUTE) {
// reset all position state history to the last known position
stateStruct.position.x = lastKnownPositionNE.x;
@ -92,10 +98,10 @@ void NavEKF2_core::ResetPosition(void)
// Use GPS data as first preference if fresh data is available
if (imuSampleTime_ms - lastTimeGpsReceived_ms < 250) {
// record the ID of the GPS for the data we are using for the reset
last_gps_idx = gpsDataNew.sensor_idx;
last_gps_idx = gps_corrected.sensor_idx;
// write to state vector and compensate for offset between last GPS measurement and the EKF time horizon
stateStruct.position.x = gpsDataNew.pos.x + 0.001f*gpsDataNew.vel.x*(float(imuDataDelayed.time_ms) - float(gpsDataNew.time_ms));
stateStruct.position.y = gpsDataNew.pos.y + 0.001f*gpsDataNew.vel.y*(float(imuDataDelayed.time_ms) - float(gpsDataNew.time_ms));
stateStruct.position.x = gps_corrected.pos.x + 0.001f*gps_corrected.vel.x*(float(imuDataDelayed.time_ms) - float(gps_corrected.time_ms));
stateStruct.position.y = gps_corrected.pos.y + 0.001f*gps_corrected.vel.y*(float(imuDataDelayed.time_ms) - float(gps_corrected.time_ms));
// set the variances using the position measurement noise parameter
P[6][6] = P[7][7] = sq(MAX(gpsPosAccuracy,frontend->_gpsHorizPosNoise));
// clear the timeout flags and counters
@ -241,6 +247,33 @@ bool NavEKF2_core::resetHeightDatum(void)
return true;
}
/*
correct GPS data for position offset of antenna phase centre relative to the IMU
*/
void NavEKF2_core::CorrectGPSForAntennaOffset(gps_elements &gps_data)
{
const Vector3f &posOffsetBody = AP::gps().get_antenna_offset(gpsDataDelayed.sensor_idx) - accelPosOffset;
if (posOffsetBody.is_zero()) {
return;
}
// Don't fuse velocity data if GPS doesn't support it
if (fuseVelData) {
// TODO use a filtered angular rate with a group delay that matches the GPS delay
Vector3f angRate = imuDataDelayed.delAng * (1.0f/imuDataDelayed.delAngDT);
Vector3f velOffsetBody = angRate % posOffsetBody;
Vector3f velOffsetEarth = prevTnb.mul_transpose(velOffsetBody);
gps_data.vel.x -= velOffsetEarth.x;
gps_data.vel.y -= velOffsetEarth.y;
gps_data.vel.z -= velOffsetEarth.z;
}
Vector3f posOffsetEarth = prevTnb.mul_transpose(posOffsetBody);
gps_data.pos.x -= posOffsetEarth.x;
gps_data.pos.y -= posOffsetEarth.y;
gps_data.hgt += posOffsetEarth.z;
}
/********************************************************
* FUSE MEASURED_DATA *
********************************************************/
@ -274,25 +307,8 @@ void NavEKF2_core::SelectVelPosFusion()
fusePosData = true;
extNavUsedForPos = false;
// correct GPS data for position offset of antenna phase centre relative to the IMU
Vector3f posOffsetBody = AP::gps().get_antenna_offset(gpsDataDelayed.sensor_idx) - accelPosOffset;
if (!posOffsetBody.is_zero()) {
// Don't fuse velocity data if GPS doesn't support it
if (fuseVelData) {
// TODO use a filtered angular rate with a group delay that matches the GPS delay
Vector3f angRate = imuDataDelayed.delAng * (1.0f/imuDataDelayed.delAngDT);
Vector3f velOffsetBody = angRate % posOffsetBody;
Vector3f velOffsetEarth = prevTnb.mul_transpose(velOffsetBody);
gpsDataDelayed.vel.x -= velOffsetEarth.x;
gpsDataDelayed.vel.y -= velOffsetEarth.y;
gpsDataDelayed.vel.z -= velOffsetEarth.z;
}
Vector3f posOffsetEarth = prevTnb.mul_transpose(posOffsetBody);
gpsDataDelayed.pos.x -= posOffsetEarth.x;
gpsDataDelayed.pos.y -= posOffsetEarth.y;
gpsDataDelayed.hgt += posOffsetEarth.z;
}
// correct for antenna position
CorrectGPSForAntennaOffset(gpsDataDelayed);
// copy corrected GPS data to observation vector
if (fuseVelData) {
@ -354,8 +370,8 @@ void NavEKF2_core::SelectVelPosFusion()
posResetNE.y = stateStruct.position.y;
// Set the position states to the position from the new GPS
stateStruct.position.x = gpsDataNew.pos.x;
stateStruct.position.y = gpsDataNew.pos.y;
stateStruct.position.x = gpsDataDelayed.pos.x;
stateStruct.position.y = gpsDataDelayed.pos.y;
// Calculate the position offset due to the reset
posResetNE.x = stateStruct.position.x - posResetNE.x;

5
libraries/AP_NavEKF2/AP_NavEKF2_core.h
View File

@ -775,7 +775,10 @@ private:
// update timing statistics structure
void updateTimingStatistics(void);
// correct gps data for antenna position
void CorrectGPSForAntennaOffset(gps_elements &gps_data);
// Length of FIFO buffers used for non-IMU sensor data.
// Must be larger than the time period defined by IMU_BUFFER_LENGTH
static const uint32_t OBS_BUFFER_LENGTH = 5;