mirror of https://github.com/ArduPilot/ardupilot
AP_NavEKF: Fix bug in optical flow fusion smoothing
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@ -397,6 +397,7 @@ NavEKF::NavEKF(const AP_AHRS *ahrs, AP_Baro &baro) :
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_msecMagAvg = 100; // average number of msec between magnetometer measurements
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_msecBetaAvg = 100; // average number of msec between synthetic sideslip measurements
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_msecBetaMax = 200; // maximum number of msec between synthetic sideslip measurements
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_msecFlowAvg = 100; // average number of msec between optical flow measurements
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dtVelPos = 0.02; // number of seconds between position and velocity corrections. This should be a multiple of the imu update interval.
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// Misc initial conditions
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@ -545,7 +546,7 @@ void NavEKF::InitialiseFilterDynamic(void)
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dtIMU = constrain_float(_ahrs->get_ins().get_delta_time(),0.001f,1.0f);
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dtIMUinv = 1.0f / dtIMU;
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// If we have a high rate update step of >100 Hz, then there may not enough time to all the fusion steps at once, so load levelling is used
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// If we have a high rate update step of >100 Hz, then there may not be enough time to do all the fusion steps at once, so load levelling is used
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if (dtIMU < 0.009f) {
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inhibitLoadLeveling = false;
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} else {
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@ -558,6 +559,8 @@ void NavEKF::InitialiseFilterDynamic(void)
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hgtUpdateCountMax = uint8_t(1.0f/hgtUpdateCountMaxInv);
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magUpdateCountMaxInv = (dtIMU * 1000.0f)/float(_msecMagAvg);
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magUpdateCountMax = uint8_t(1.0f/magUpdateCountMaxInv);
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flowUpdateCountMaxInv = (dtIMU * 1000.0f)/float(_msecFlowAvg);
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flowUpdateCountMax = uint8_t(1.0f/flowUpdateCountMaxInv);
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// calculate initial orientation and earth magnetic field states
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state.quat = calcQuatAndFieldStates(_ahrs->roll, _ahrs->pitch);
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@ -931,6 +934,9 @@ void NavEKF::SelectFlowFusion()
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// if the filter is initialised, we have data to fuse and the vehicle is not excessively tilted, then perform optical flow fusion
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if (useOptFlow() && newDataFlow && tiltOK && !delayFusion && !staticMode)
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{
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// reset state updates and counter used to spread fusion updates across several frames to reduce 10Hz pulsing
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memset(&flowIncrStateDelta[0], 0, sizeof(flowIncrStateDelta));
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flowUpdateCount = 0;
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// Set the flow noise used by the fusion processes
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R_LOS = sq(max(_flowNoise, 0.05f));
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// Fuse the optical flow X axis data into the main filter
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@ -944,6 +950,7 @@ void NavEKF::SelectFlowFusion()
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flowFusePerformed = true;
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// update the time stamp
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prevFlowFusionTime_ms = imuSampleTime_ms;
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} else if (flow_state.obsIndex == 1 && !delayFusion){
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// Fuse the optical flow Y axis data into the main filter
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FuseOptFlow();
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@ -3020,10 +3027,10 @@ void NavEKF::FuseOptFlow()
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}
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// Attitude, velocity and position corrections are averaged across multiple prediction cycles between now and the anticipated time for the next measurement.
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// Don't do averaging of quaternion state corrections if total angle change across predicted interval is going to exceed 0.1 rad
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bool highRates = ((magUpdateCountMax * correctedDelAng.length()) > 0.1f);
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// Calculate the number of averaging frames left to go. This is required becasue magnetometer fusion is applied across three consecutive prediction cycles
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bool highRates = ((flowUpdateCountMax * correctedDelAng.length()) > 0.1f);
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// Calculate the number of averaging frames left to go. This is required because flow fusion is applied across two consecutive prediction cycles
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// There is no point averaging if the number of cycles left is less than 2
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float minorFramesToGo = float(magUpdateCountMax) - float(magUpdateCount);
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float minorFramesToGo = float(flowUpdateCountMax) - float(flowUpdateCount);
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for (uint8_t i = 0; i<=21; i++) {
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if ((i <= 3 && highRates) || i >= 10 || minorFramesToGo < 1.5f) {
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states[i] = states[i] - Kfusion[i] * innovOptFlow[obsIndex];
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@ -4292,6 +4299,7 @@ void NavEKF::ZeroVariables()
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memset(&gpsIncrStateDelta[0], 0, sizeof(gpsIncrStateDelta));
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memset(&hgtIncrStateDelta[0], 0, sizeof(hgtIncrStateDelta));
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memset(&magIncrStateDelta[0], 0, sizeof(magIncrStateDelta));
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memset(&flowIncrStateDelta[0], 0, sizeof(flowIncrStateDelta));
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gpsPosGlitchOffsetNE.zero();
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// optical flow variables
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newDataFlow = false;
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@ -545,7 +545,7 @@ private:
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// Used by smoothing of state corrections
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float gpsIncrStateDelta[10]; // vector of corrections to attitude, velocity and position to be applied over the period between the current and next GPS measurement
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float hgtIncrStateDelta[10]; // vector of corrections to attitude, velocity and position to be applied over the period between the current and next height measurement
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float flowIncrStateDelta[10]; // vector of corrections to attitude, velocity and position to be applied over the period between the current and next magnetometer measurement
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float magIncrStateDelta[10]; // vector of corrections to attitude, velocity and position to be applied over the period between the current and next magnetometer measurement
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uint8_t gpsUpdateCount; // count of the number of minor state corrections using GPS data
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uint8_t gpsUpdateCountMax; // limit on the number of minor state corrections using GPS data
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float gpsUpdateCountMaxInv; // floating point inverse of gpsFilterCountMax
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@ -595,14 +595,15 @@ private:
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float R_LOS; // variance of optical flow rate measurements (rad/sec)^2
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float auxRngTestRatio; // square of range finder innovations divided by fail threshold used by main filter where >1.0 is a fail
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Vector2f flowGyroBias; // bias error of optical flow sensor gyro output
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float magIncrStateDelta[10]; // vector of corrections to attitude, velocity and position to be applied over the period between the current and next magnetometer measurement
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uint8_t flowUpdateCount; // count of the number of minor state corrections using optical flow data
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uint8_t flowUpdateCountMax; // limit on the number of minor state corrections using optical flow data
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float flowUpdateCountMaxInv; // floating point inverse of flowUpdateCountMax
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float flowIncrStateDelta[10]; // vector of corrections to attitude, velocity and position to be applied over the period between the current and next magnetometer measurement
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bool newDataRng; // true when new valid range finder data has arrived.
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bool velHoldMode; // true when holding velocity in optical flow mode when no flow measurements are available
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bool lastHoldVelocity; // last value of holdVelocity
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Vector2f heldVelNE; // velocity held when no aiding is available
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uint16_t _msecFlowAvg; // average number of msec between synthetic sideslip measurements
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// states held by optical flow fusion across time steps
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// optical flow X,Y motion compensated rate measurements are fused across two time steps
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