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flow: restructure optical flow control logic (#928)
- extract motion checks performed on ground - move all non-timing check to controlOpticalFlowFusion. This simplifies and standardirzes the setOpticalFlowData function. Furthermore, in some cases (SITL, PX4Flow), the dt is forced to 0 when the quality is 0 (which is usual on ground) so the ekf needs to ignore those values on ground to initialize properly the flow fusion. - add filter convergence test - move check for dt time max in setOpticalFlowData - in the simulator, do not update dt as this is the sensor integration period.
This commit is contained in:
Mathieu Bresciani
+101
-82
@@ -144,12 +144,13 @@ void Ekf::controlFusionModes()
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// This means we stop looking for new data until the old data has been fused, unless we are not fusing optical flow,
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// in this case we need to empty the buffer
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if (!_flow_data_ready || !_control_status.flags.opt_flow) {
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_flow_data_ready = _flow_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_flow_sample_delayed)
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&& (_R_to_earth(2, 2) > _params.range_cos_max_tilt);
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_flow_data_ready = _flow_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_flow_sample_delayed);
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}
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// check if we should fuse flow data for terrain estimation
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if (!_flow_for_terrain_data_ready && _flow_data_ready && _control_status.flags.in_air) {
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// TODO: WARNING, _flow_data_ready can be modified in controlOpticalFlowFusion
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// due to some checks failing
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// only fuse flow for terrain if range data hasn't been fused for 5 seconds
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_flow_for_terrain_data_ready = isTimedOut(_time_last_hagl_fuse, (uint64_t)5E6);
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// only fuse flow for terrain if the main filter is not fusing flow and we are using gps
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@@ -343,33 +344,56 @@ void Ekf::controlExternalVisionFusion()
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void Ekf::controlOpticalFlowFusion()
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{
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// TODO: These motion checks run all the time. Pull them out of this function
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// Check if on ground motion is un-suitable for use of optical flow
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if (!_control_status.flags.in_air) {
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// When on ground check if the vehicle is being shaken or moved in a way that could cause a loss of navigation
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const float accel_norm = _accel_vec_filt.norm();
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const bool motion_is_excessive = ((accel_norm > (CONSTANTS_ONE_G * 1.5f)) // upper g limit
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|| (accel_norm < (CONSTANTS_ONE_G * 0.5f)) // lower g limit
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|| (_ang_rate_magnitude_filt > _flow_max_rate) // angular rate exceeds flow sensor limit
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|| (_R_to_earth(2,2) < cosf(math::radians(30.0f)))); // tilted excessively
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if (motion_is_excessive) {
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_time_bad_motion_us = _imu_sample_delayed.time_us;
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} else {
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_time_good_motion_us = _imu_sample_delayed.time_us;
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}
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updateOnGroundMotionForOpticalFlowChecks();
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} else {
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_time_bad_motion_us = 0;
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_time_good_motion_us = _imu_sample_delayed.time_us;
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resetOnGroundMotionForOpticalFlowChecks();
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}
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// Accumulate autopilot gyro data across the same time interval as the flow sensor
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_imu_del_ang_of += _imu_sample_delayed.delta_ang - _state.delta_ang_bias;
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_delta_time_of += _imu_sample_delayed.delta_ang_dt;
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if (_flow_data_ready) {
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const bool is_quality_good = (_flow_sample_delayed.quality >= _params.flow_qual_min);
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const bool is_magnitude_good = !_flow_sample_delayed.flow_xy_rad.longerThan(_flow_sample_delayed.dt * _flow_max_rate);
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const bool is_tilt_good = (_R_to_earth(2, 2) > _params.range_cos_max_tilt);
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const float delta_time_min = fmaxf(0.8f * _delta_time_of, 0.001f);
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const float delta_time_max = fminf(1.2f * _delta_time_of, 0.2f);
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const bool is_delta_time_good = _flow_sample_delayed.dt >= delta_time_min
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&& _flow_sample_delayed.dt <= delta_time_max;
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const bool is_body_rate_comp_available = calcOptFlowBodyRateComp();
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if (is_quality_good
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&& is_magnitude_good
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&& is_tilt_good
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&& is_body_rate_comp_available
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&& is_delta_time_good) {
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// compensate for body motion to give a LOS rate
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_flow_compensated_XY_rad = _flow_sample_delayed.flow_xy_rad - _flow_sample_delayed.gyro_xyz.xy();
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} else if (!_control_status.flags.in_air && is_body_rate_comp_available) {
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if (!is_delta_time_good) {
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// handle special case of SITL and PX4Flow where dt is forced to
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// zero when the quaity is 0
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_flow_sample_delayed.dt = delta_time_min;
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}
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// when on the ground with poor flow quality,
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// assume zero ground relative velocity and LOS rate
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_flow_compensated_XY_rad.setZero();
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} else {
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// don't use this flow data and wait for the next data to arrive
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_flow_data_ready = false;
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_flow_for_terrain_data_ready = false; // TODO: find a better place
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}
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}
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// New optical flow data is available and is ready to be fused when the midpoint of the sample falls behind the fusion time horizon
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if (_flow_data_ready) {
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// Inhibit flow use if motion is un-suitable or we have good quality GPS
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@@ -377,47 +401,38 @@ void Ekf::controlOpticalFlowFusion()
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const float gps_err_norm_lim = _control_status.flags.opt_flow ? 0.7f : 1.0f;
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// Check if we are in-air and require optical flow to control position drift
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bool flow_required = _control_status.flags.in_air &&
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(_is_dead_reckoning // is doing inertial dead-reckoning so must constrain drift urgently
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|| (isOnlyActiveSourceOfHorizontalAiding(_control_status.flags.opt_flow))
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|| (_control_status.flags.gps && (_gps_error_norm > gps_err_norm_lim))); // is using GPS, but GPS is bad
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const bool is_flow_required = _control_status.flags.in_air
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&& (_is_dead_reckoning // is doing inertial dead-reckoning so must constrain drift urgently
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|| isOnlyActiveSourceOfHorizontalAiding(_control_status.flags.opt_flow)
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|| (_control_status.flags.gps && (_gps_error_norm > gps_err_norm_lim))); // is using GPS, but GPS is bad
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if (!_inhibit_flow_use && _control_status.flags.opt_flow) {
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// inhibit use of optical flow if motion is unsuitable and we are not reliant on it for flight navigation
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bool preflight_motion_not_ok = !_control_status.flags.in_air && ((_imu_sample_delayed.time_us - _time_good_motion_us) > (uint64_t)1E5);
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bool flight_motion_not_ok = _control_status.flags.in_air && !isTerrainEstimateValid();
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if ((preflight_motion_not_ok || flight_motion_not_ok) && !flow_required) {
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_inhibit_flow_use = true;
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}
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} else if (_inhibit_flow_use && !_control_status.flags.opt_flow){
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// allow use of optical flow if motion is suitable or we are reliant on it for flight navigation
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bool preflight_motion_ok = !_control_status.flags.in_air && ((_imu_sample_delayed.time_us - _time_bad_motion_us) > (uint64_t)5E6);
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bool flight_motion_ok = _control_status.flags.in_air && isRangeAidSuitable();
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if (preflight_motion_ok || flight_motion_ok || flow_required) {
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_inhibit_flow_use = false;
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}
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}
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// Handle cases where we are using optical flow but are no longer able to because data is old
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// or its use has been inhibited.
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// inhibit use of optical flow if motion is unsuitable and we are not reliant on it for flight navigation
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const bool preflight_motion_not_ok = !_control_status.flags.in_air
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&& ((_imu_sample_delayed.time_us > (_time_good_motion_us + (uint64_t)1E5))
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|| (_imu_sample_delayed.time_us < (_time_bad_motion_us + (uint64_t)5E6)));
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const bool flight_condition_not_ok = _control_status.flags.in_air && !isTerrainEstimateValid();
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_inhibit_flow_use = ((preflight_motion_not_ok || flight_condition_not_ok) && !is_flow_required)
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|| !_control_status.flags.tilt_align;
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// Handle cases where we are using optical flow but we should not use it anymore
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if (_control_status.flags.opt_flow) {
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if (_inhibit_flow_use) {
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stopFlowFusion();
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_time_last_of_fuse = 0;
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if (!(_params.fusion_mode & MASK_USE_OF)
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|| _inhibit_flow_use) {
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} else if (isTimedOut(_time_last_of_fuse, (uint64_t)_params.reset_timeout_max)) {
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stopFlowFusion();
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return;
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}
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}
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// optical flow fusion mode selection logic
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if ((_params.fusion_mode & MASK_USE_OF) // optical flow has been selected by the user
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&& !_control_status.flags.opt_flow // we are not yet using flow data
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&& _control_status.flags.tilt_align // we know our tilt attitude
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&& !_inhibit_flow_use
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&& isTerrainEstimateValid())
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&& !_inhibit_flow_use)
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{
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// If the heading is not aligned, reset the yaw and magnetic field states
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// TODO: ekf2 should always try to align itself if not already aligned
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if (!_control_status.flags.yaw_align) {
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_control_status.flags.yaw_align = resetMagHeading(_mag_lpf.getState());
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}
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@@ -430,61 +445,65 @@ void Ekf::controlOpticalFlowFusion()
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// if we are not using GPS or external vision aiding, then the velocity and position states and covariances need to be set
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const bool flow_aid_only = !isOtherSourceOfHorizontalAidingThan(_control_status.flags.opt_flow);
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if (flow_aid_only) {
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// TODO: Issue: First time we want to reset the optical flow velocity
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// we will use _flow_compensated_XY_rad in the resetVelocity() function,
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// but _flow_compensated_XY_rad is this zero as it gets updated for the first time below here.
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resetVelocity();
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resetHorizontalPosition();
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}
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}
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} else if (!(_params.fusion_mode & MASK_USE_OF)) {
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_control_status.flags.opt_flow = false;
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}
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// handle the case when we have optical flow, are reliant on it, but have not been using it for an extended period
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if (isOnlyActiveSourceOfHorizontalAiding(_control_status.flags.opt_flow)) {
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if (_control_status.flags.opt_flow) {
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// Wait until the midpoint of the flow sample has fallen behind the fusion time horizon
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if (_imu_sample_delayed.time_us > (_flow_sample_delayed.time_us - uint32_t(1e6f * _flow_sample_delayed.dt) / 2)) {
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// Fuse optical flow LOS rate observations into the main filter only if height above ground has been updated recently
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// but use a relaxed time criteria to enable it to coast through bad range finder data
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if (isRecent(_time_last_hagl_fuse, (uint64_t)10e6)) {
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fuseOptFlow();
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_last_known_posNE = _state.pos.xy();
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}
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bool do_reset = isTimedOut(_time_last_of_fuse, _params.reset_timeout_max);
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_flow_data_ready = false;
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}
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// handle the case when we have optical flow, are reliant on it, but have not been using it for an extended period
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if (isTimedOut(_time_last_of_fuse, _params.reset_timeout_max)
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&& !isOtherSourceOfHorizontalAidingThan(_control_status.flags.opt_flow)) {
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if (do_reset) {
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resetVelocity();
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resetHorizontalPosition();
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}
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}
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// Only fuse optical flow if valid body rate compensation data is available
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if (calcOptFlowBodyRateComp()) {
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bool flow_quality_good = (_flow_sample_delayed.quality >= _params.flow_qual_min);
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if (!flow_quality_good && !_control_status.flags.in_air) {
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// when on the ground with poor flow quality, assume zero ground relative velocity and LOS rate
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_flow_compensated_XY_rad.setZero();
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} else {
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// compensate for body motion to give a LOS rate
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_flow_compensated_XY_rad = _flow_sample_delayed.flow_xy_rad - _flow_sample_delayed.gyro_xyz.xy();
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}
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} else {
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// don't use this flow data and wait for the next data to arrive
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_flow_data_ready = false;
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}
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} else if (_control_status.flags.opt_flow && (_imu_sample_delayed.time_us > _flow_sample_delayed.time_us + (uint64_t)10e6)) {
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stopFlowFusion();
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}
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}
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// Wait until the midpoint of the flow sample has fallen behind the fusion time horizon
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if (_flow_data_ready && (_imu_sample_delayed.time_us > _flow_sample_delayed.time_us - uint32_t(1e6f * _flow_sample_delayed.dt) / 2)) {
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// Fuse optical flow LOS rate observations into the main filter only if height above ground has been updated recently
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// but use a relaxed time criteria to enable it to coast through bad range finder data
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if (_control_status.flags.opt_flow && isRecent(_time_last_hagl_fuse, (uint64_t)10e6)) {
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fuseOptFlow();
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_last_known_posNE = _state.pos.xy();
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}
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void Ekf::updateOnGroundMotionForOpticalFlowChecks()
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{
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// When on ground check if the vehicle is being shaken or moved in a way that could cause a loss of navigation
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const float accel_norm = _accel_vec_filt.norm();
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_flow_data_ready = false;
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const bool motion_is_excessive = ((accel_norm > (CONSTANTS_ONE_G * 1.5f)) // upper g limit
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|| (accel_norm < (CONSTANTS_ONE_G * 0.5f)) // lower g limit
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|| (_ang_rate_magnitude_filt > _flow_max_rate) // angular rate exceeds flow sensor limit
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|| (_R_to_earth(2,2) < cosf(math::radians(30.0f)))); // tilted excessively
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if (motion_is_excessive) {
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_time_bad_motion_us = _imu_sample_delayed.time_us;
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} else {
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_time_good_motion_us = _imu_sample_delayed.time_us;
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}
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}
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void Ekf::resetOnGroundMotionForOpticalFlowChecks()
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{
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_time_bad_motion_us = 0;
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_time_good_motion_us = _imu_sample_delayed.time_us;
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}
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void Ekf::controlGpsFusion()
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{
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// Check for new GPS data that has fallen behind the fusion time horizon
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