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Robustify range finder kinematic consistency check #22117

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merged 1 commit into from
Sep 22, 2023
Merged

Robustify range finder kinematic consistency check #22117

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20 changes: 16 additions & 4 deletions src/modules/ekf2/EKF/range_finder_consistency_check.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -37,8 +37,12 @@

#include "range_finder_consistency_check.hpp"

void RangeFinderConsistencyCheck::update(float dist_bottom, float dist_bottom_var, float vz, float vz_var, uint64_t time_us)
void RangeFinderConsistencyCheck::update(float dist_bottom, float dist_bottom_var, float vz, float vz_var, bool horizontal_motion, uint64_t time_us)
{
if (horizontal_motion) {
_time_last_horizontal_motion = time_us;
}

const float dt = static_cast<float>(time_us - _time_last_update_us) * 1e-6f;

if ((_time_last_update_us == 0)
Expand Down Expand Up @@ -68,12 +72,20 @@ void RangeFinderConsistencyCheck::update(float dist_bottom, float dist_bottom_va

void RangeFinderConsistencyCheck::updateConsistency(float vz, uint64_t time_us)
{
if (fabsf(vz) < _min_vz_for_valid_consistency) {
// We can only check consistency if there is vertical motion
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Wouldn't you want to still invalidate if there's horizontal motion?

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No, we can validate regardless of the horizontal motion, but we can only invalidate if we're only moving vertically, otherwise a change in terrain height would invalidate too.

return;
}

if (fabsf(_signed_test_ratio_lpf.getState()) >= 1.f) {
_is_kinematically_consistent = false;
_time_last_inconsistent_us = time_us;
if ((time_us - _time_last_horizontal_motion) > _signed_test_ratio_tau) {
_is_kinematically_consistent = false;
_time_last_inconsistent_us = time_us;
}

} else {
if (fabsf(vz) > _min_vz_for_valid_consistency && _test_ratio < 1.f && ((time_us - _time_last_inconsistent_us) > _consistency_hyst_time_us)) {
if (_test_ratio < 1.f
&& ((time_us - _time_last_inconsistent_us) > _consistency_hyst_time_us)) {
_is_kinematically_consistent = true;
}
}
Expand Down
3 changes: 2 additions & 1 deletion src/modules/ekf2/EKF/range_finder_consistency_check.hpp
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Expand Up @@ -48,7 +48,7 @@ class RangeFinderConsistencyCheck final
RangeFinderConsistencyCheck() = default;
~RangeFinderConsistencyCheck() = default;

void update(float dist_bottom, float dist_bottom_var, float vz, float vz_var, uint64_t time_us);
void update(float dist_bottom, float dist_bottom_var, float vz, float vz_var, bool horizontal_motion, uint64_t time_us);

void setGate(float gate) { _gate = gate; }

Expand All @@ -72,6 +72,7 @@ class RangeFinderConsistencyCheck final

bool _is_kinematically_consistent{true};
uint64_t _time_last_inconsistent_us{};
uint64_t _time_last_horizontal_motion{};

static constexpr float _signed_test_ratio_tau = 2.f;

Expand Down
8 changes: 4 additions & 4 deletions src/modules/ekf2/EKF/range_height_control.cpp
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Expand Up @@ -62,15 +62,15 @@ void Ekf::controlRangeHeightFusion()
const Vector3f pos_offset_earth = _R_to_earth * pos_offset_body;
_range_sensor.setRange(_range_sensor.getRange() + pos_offset_earth(2) / _range_sensor.getCosTilt());

// Run the kinematic consistency check when not moving horizontally
if (_control_status.flags.in_air && !_control_status.flags.fixed_wing
&& (sq(_state.vel(0)) + sq(_state.vel(1)) < fmaxf(P.trace<2>(State::vel.idx), 0.1f))) {
if (_control_status.flags.in_air) {
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What's the harm in letting this always run (!in_air)? The actual usage in the terrain estimator is still going to require in_air && rng_kin_consistent.

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An issue I see is when the operator is powering the drone but is still manipulating it before takeoff. There is then a high chance to fail the consistency check for no real reason. It should then be validated again after takeoff, so in theory it's not a big problem, the terrain estimator will just start a bit later and the 5s of no terrain aiding timeout should be enough.

const bool horizontal_motion = _control_status.flags.fixed_wing
|| (sq(_state.vel(0)) + sq(_state.vel(1)) > fmaxf(P.trace<2>(State::vel.idx), 0.1f));

const float dist_dependant_var = sq(_params.range_noise_scaler * _range_sensor.getDistBottom());
const float var = sq(_params.range_noise) + dist_dependant_var;

_rng_consistency_check.setGate(_params.range_kin_consistency_gate);
_rng_consistency_check.update(_range_sensor.getDistBottom(), math::max(var, 0.001f), _state.vel(2), P(State::vel.idx + 2, State::vel.idx + 2), _time_delayed_us);
_rng_consistency_check.update(_range_sensor.getDistBottom(), math::max(var, 0.001f), _state.vel(2), P(State::vel.idx + 2, State::vel.idx + 2), horizontal_motion, _time_delayed_us);
}

} else {
Expand Down
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